reconcile '[]' and [] (#644), solve remaining conformity issues (#648), move (-->) from dcgs.pl to builtins.pl (#649)

Improved readline

.dockerignore

@@ -0,0 +1,6 @@
+target
+Dockerfile
+README.md
+.git
+.gitignore
+.gitmodules

.gitignore

@@ -1,4 +1,3 @@
 target/
-Cargo.lock
 
 

.travis.yml

@@ -1,13 +1,31 @@
 language: rust
-rust:
-    - stable
-    - beta
-    - nightly
-matrix:
-    allow_failures:
-        - rust: nightly
-    fast_finish: true
+cache: cargo
+os: linux
+dist: xenial
 
-script:
-    - cargo build --verbose --all
-    - cargo test --verbose --all
+before_script:
+  - cargo fetch
+
+jobs:
+  allow_failures:
+    env:
+      - CAN_FAIL=true
+  include:
+  - stage: "Stable: Build"
+    rust: stable
+    script: cargo rustc --verbose -- -D warnings
+    name: "Build Stable"
+  - stage: "Stable: Tests"
+    rust: stable
+    script: cargo test --verbose --all
+    name: "Tests Stable"
+  - stage: "Features"
+    rust: stable
+    script: cargo test --verbose --all --no-default-features --features num
+    name: "num Tests"
+    env: CAN_FAIL=true
+  - stage: "Beta: Build"
+  # - #
+    rust: beta
+    script: cargo rustc --verbose -- -D warnings
+    name: "Build Beta"

Cargo.toml

@@ -1,28 +1,50 @@
 [package]
 name = "scryer-prolog"
-version = "0.8.112"
+version = "0.8.127"
 authors = ["Mark Thom <markjordanthom@gmail.com>"]
-build = "build.rs"
-repository = "https://github.com/mthom/scryer-prolog"
-description = "A modern Prolog implementation written mostly in Rust."
-license = "BSD-3-Clause"
 edition = "2018"
+description = "A modern Prolog implementation written mostly in Rust."
+readme = "README.md"
+repository = "https://github.com/mthom/scryer-prolog"
+license = "BSD-3-Clause"
+keywords = ["prolog", "prolog-interpreter", "prolog-system"]
+categories = ["command-line-utilities"]
+build = "build.rs"
 
 [build-dependencies]
 indexmap = "1.0.2"
 
+[features]
+default = ["rug", "prolog_parser/rug"]
+num = ["num-rug-adapter", "prolog_parser/num"]
+
 [dependencies]
+cpu-time = "1.0.0"
+crossterm = "0.16.0"
 dirs = "2.0.2"
+divrem = "0.1.0"
 downcast = "0.10.0"
+git-version = "0.3.4"
+hostname = "0.3.1"
 indexmap = "1.0.2"
 lazy_static = "1.4.0"
 libc = "0.2.62"
 nix = "0.15.0"
+num-rug-adapter = { optional = true, version = "0.1.3" }
 ordered-float = "0.5.0"
-prolog_parser = "0.8.33"
+prolog_parser = { version = "0.8.65", default-features = false }
 ref_thread_local = "0.0.0"
-rug = "1.4.0"
-rustyline = "5.0.3"
-
-[dependencies.termion]
-version = "1.4.0"
+rug = { version = "1.4.0", optional = true }
+rustyline = "6.0.0"
+unicode_reader = "1.0.0"
+ring = "0.16.13"
+ripemd160 = "0.8.0"
+sha3 = "0.8.2"
+blake2 = "0.8.1"
+openssl = { version = "0.10.29", features = ["vendored"] }
+native-tls = "0.2.4"
+chrono = "0.4.11"
+select = "0.4.3"
+roxmltree = "0.11.0"
+base64 = "0.12.3"
+sodiumoxide = "0.2.6"

Dockerfile

@@ -0,0 +1,30 @@
+# Based on https://hub.docker.com/_/rust?tab=description and https://blog.sedrik.se/posts/my-docker-setup-for-rust/
+
+# The first container is for build purposes only.
+FROM rust as builder
+
+WORKDIR /usr/src/scryer-prolog
+
+# Using a dummy build.rs and src/main.rs with your Cargo.toml lets Docker cache your Rust dependencies and not rebuild
+# them every time.
+COPY Cargo.toml .
+COPY Cargo.lock .
+RUN mkdir -p src
+RUN echo "fn main() {}" > src/main.rs
+RUN echo "fn main() {}" > build.rs
+RUN cargo build --release
+
+# We need to touch our real main.rs and build.rs files or else
+# docker will use the cached ones.
+COPY . .
+RUN touch src/main.rs
+RUN touch build.rs
+
+RUN cargo build --release
+
+RUN ls ./target/release
+
+# Finally, copy the scryer-prolog executable to a slimmer container.
+FROM debian:buster-slim
+COPY --from=builder /usr/src/scryer-prolog/target/release/scryer-prolog /usr/local/bin/scryer-prolog
+CMD ["scryer-prolog"]

README.md

@@ -5,6 +5,8 @@ source industrial strength production environment that is also a
 testbed for bleeding edge research in logic and constraint
 programming, which is itself written in a high-level language.
 
+![Scryer Logo: Cryer](logo/scryer.png)
+
 ## Phase 1
 
 Produce an implementation of the Warren Abstract Machine in Rust, done
@@ -30,10 +32,8 @@ Extend Scryer Prolog to include the following, among other features:
 - [x] Built-in predicates for list processing and top-level declarative
       control (`setup_call_cleanup/3`, `call_with_inference_limit/3`,
       etc.)
-- [x] Default representation of strings as list of chars, using a packed
-      internal representation.
-        - A representation of 'partial strings' as difference lists
-          of characters.
+- [x] ~~Default representation of strings as lists of characters, using a packed
+      internal representation.~~
 - [x] `term_expansion/2` and `goal_expansion/2`.
 - [x] Definite Clause Grammars.
 - [x] Attributed variables using the SICStus Prolog interface and
@@ -42,7 +42,7 @@ Extend Scryer Prolog to include the following, among other features:
   - [x] Support for `verify_attributes/3`
   - [x] Support for `attribute_goals/2` and `project_attributes/2`
   - [x] `call_residue_vars/2`
-- [x] `if_` and related predicates, following the developments of the
+- [x] `if_/3` and related predicates, following the developments of the
       paper "Indexing `dif/2`".
 - [x] All-solutions predicates (`findall/{3,4}`, `bagof/3`, `setof/3`, `forall/2`).
 - [x] Clause creation and destruction (`asserta/1`, `assertz/1`,
@@ -50,11 +50,20 @@ Extend Scryer Prolog to include the following, among other features:
 - [x] Backtrackable and non-backtrackable global variables via `bb_get/2`
       `bb_put/2` (non-backtrackable) and `bb_b_put/2`
       (backtrackable).
-- [ ] Streams and predicates for stream control (_in progress_).
-- [ ] An incremental compacting garbage collector satisfying the five
+- [x] Delimited continuations based on reset/3, shift/1 (documented in
+      "Delimited Continuations for Prolog").
+- [x] Tabling library based on delimited continuations
+      (documented in "Tabling as a Library with Delimited Control").
+- [x] A _redone_ representation of strings as difference lists of
+      characters, using a packed internal representation.
+- [x] clp(B) and clp(ℤ) as builtin libraries.
+- [x] Streams and predicates for stream control.
+  - [x] A simple sockets library representing TCP connections as streams.  
+- [ ] Incremental compilation and loading process, newly written,
+      primarily in Prolog. (_in progress_)
+- [ ] A compacting garbage collector satisfying the five
       properties of "Precise Garbage Collection in Prolog."
 - [ ] Mode declarations.
-- [ ] Extensions for clp(FD).
 
 ## Phase 3
 
@@ -79,218 +88,127 @@ Programming?"
 unum implementation or an ad hoc one. Unums are described in
 Gustafson's book "The End of Error."
 
-3. Add support for shift/reset delimited continuations, see "Delimited
-Continuations for Prolog."
-
-4. Add concurrent tables to manage shared references to atoms and
+3. Add concurrent tables to manage shared references to atoms and
 strings.
 
-5. Add optional SLG resolution for fast memoization of predicates.
-
-6. Add some form of JIT predicate indexing.
+4. Add some form of JIT predicate indexing.
 
 ## Installing Scryer Prolog
 
+### Native Install (Unix Only)
+
 First, install the latest stable version of
 [Rust](https://www.rust-lang.org/en-US/install.html) using your
-preferred method. Then install the latest Scryer Prolog with cargo,
-like so:
+preferred method. Scryer tends to use features from newer Rust
+releases, whereas Rust packages in Linux distributions, Macports,
+etc. tend to lag behind. [rustup](http://rustup.rs) will keep your
+Rust updated to the latest stable release; any existing Rust
+distribution should be uninstalled from your system before rustup is
+used.
+
+Scryer Prolog can be installed with cargo, like so:
 
 ```
 $> cargo install scryer-prolog
 ```
 
 cargo will download and install the libraries Scryer Prolog uses
-automatically. You can find the `scryer-prolog` executable in
-`~/.cargo/bin`.
+automatically from crates.io. You can find the `scryer-prolog`
+executable in `~/.cargo/bin`.
 
-Note on compatibility: Scryer Prolog should work on Linux, Mac OS X,
-and BSD variants on which Rust runs. Windows support hinges on
-rustyline and Termion being functional in that environment, which to
-my knowledge is not currently the case.
+Publishing Rust crates to crates.io and pushing to git are entirely
+distinct, independent processes, so to be sure you have the latest
+commit, it is recommended to clone directly from this git repository,
+which can be done as follows:
 
-## Built-in predicates
+```
+$> git clone https://github.com/mthom/scryer-prolog
+$> cd scryer-prolog
+$> cargo run [--release]
+```
 
-The following predicates are built-in to Scryer.
+The optional `--release` flag will perform various optimizations,
+producing a faster executable.
 
-* Arithmetic support:
-    * `is/2` works for `(+)/{1,2}`, `(-)/{1,2}`, `(*)/2`, `(//)/2`, `(**)/2`,
-      `(^)/2`, `(div)/2`, `(/)/2`, `(rdiv)/2`, `(xor)/2`, `(rem)/2`,
-      `(mod)/2`, `(/\)/2`, `(\/)/2`, `(>>)/2`,`(<<)/2`, `(\)/1`,
-      `abs/1`, `sin/1`, `cos/1`, `tan/1`, `asin/1`, `acos/1`,
-      `atan/1`, `atan2/2`, `log/1`, `exp/1`, `sqrt/1`, `float/1`,
-      `truncate/1`, `round/1`, `floor/1`, `ceiling/1`, `pi/0`,
-      `min/1`, `max/1`      
-    * Comparison operators: `>`, `<`, `=<`, `>=`, `=:=`, `=\=`.
-* `(:)/2`
-* `(@>)/2`
-* `(@>=)/2`
-* `(@=<)/2`
-* `(@<)/2`
-* `(\+)/1`
-* `(==)/2`
-* `(\==)/2`
-* `(=)/2`
-* `(\=)/2`
-* `(=..)/2`
-* `(->)/2`
-* `(;)/2`
-* `abolish/1`
-* `acyclic_term/2`
-* `append/3`
-* `arg/3`
-* `asserta/1`
-* `assertz/1`
-* `atom/1`
-* `atomic/1`
-* `atom_chars/2`
-* `atom_codes/2`
-* `atom_concat/3`
-* `atom_length/2`
-* `bagof/3`
-* `bb_b_put/2`
-* `bb_get/2`
-* `bb_put/2`
-* `between/3`
-* `call/1..62`
-* `call_cleanup/2`
-* `call_with_inference_limit/3`
-* `call_residue_vars/2`
-* `can_be/2`
-* `catch/3`
-* `clause/2`
-* `compare/3`
-* `compound/1`
-* `copy_term/2`
-* `current_predicate/1`
-* `current_op/3`
-* `cyclic_term/1`
-* `dif/2`
-* `expand_goal/2`
-* `expand_term/2`
-* `fail/0`
-* `false/0`
-* `findall/{3,4}`
-* `float/1`
-* `forall/2`
-* `freeze/2`
-* `functor/3`
-* `gen_int/1`
-* `gen_nat/1`
-* `get_char/1`
-* `goal_expansion/2`
-* `ground/1`
-* `halt/0`
-* `integer/1`
-* `is_list/1`
-* `is_partial_string/1`
-* `keysort/2`
-* `length/2`
-* `maplist/2..9`
-* `member/2`
-* `memberchk/2`
-* `must_be/2`
-* `nl/0`
-* `nonvar/1`
-* `number_chars/2`
-* `number_codes/2`
-* `numbervars/2`
-* `numlist/{2,3}`
-* `once/1`
-* `op/3`
-* `partial_string/2`
-* `phrase/{2,3}`
-* `rational/1`
-* `read/1`
-* `repeat/{0,1}`
-* `retract/1`
-* `reverse/2`
-* `select/3`
-* `setof/3`
-* `setup_call_cleanup/3`
-* `sort/2`
-* `string/1`
-* `sub_atom/5`
-* `subsumes_term/2`
-* `term_expansion/2`
-* `term_variables/2`
-* `throw/1`
-* `true/0`
-* `unify_with_occurs_check/2`
-* `use_module/{1,2}`
-* `user:goal_expansion/2`
-* `user:term_expansion/2`
-* `var/1`
-* `variant/2`
-* `wam_instructions/2`
-* `write/1`
-* `write_canonical/1`
-* `writeq/1`
-* `write_term/2`
+### Docker Install (All Platforms)
+
+First, install [Docker](https://docs.docker.com/get-docker/) on Linux,
+Windows, or Mac.
+
+Once Docker is installed, you can download and run Scryer Prolog with a single
+command:
+```
+$> docker run -it mjt128/scryer-prolog
+```
+
+To consult your Prolog files, bind mount your programs folder as a
+[Docker volume](https://docs.docker.com/storage/volumes/):
+
+```
+$> docker run -v /home/user/prolog:/mnt -it mjt128/scryer-prolog
+?- consult('/mnt/program.pl').
+true.
+```
+
+This works on Windows too:
+
+```
+$> docker run -v C:\Users\user\Documents\prolog:/mnt -it mjt128/scryer-prolog
+?- consult('/mnt/program.pl').
+true.
+```
 
 ## Tutorial
-To enter a multi-clause predicate, the directive "[user]" is used.
 
-For example,
-```
-?- [user].
-(type Enter + Ctrl-D to terminate the stream when finished)
-p(f(f(X)), h(W), Y) :- g(W), h(W), f(X).
-p(X, Y, Z) :- h(Y), z(Z).
-?- [user].
-(type Enter + Ctrl-D to terminate the stream when finished)
-h(x). h(y).
-h(z).
-```
-In the example, `Enter + Ctrl-D` is used to terminate the standard
-input stream. The instructive message is always printed.
+Prolog files are loaded by specifying them as arguments on the command
+line. For example, to load `program.pl`, use:
 
-Queries are issued as
 ```
-?- p(X, Y, Z).
+$> scryer-prolog program.pl
 ```
 
-Pressing `SPACE` will backtrack through other possible answers, if any exist.
-Pressing `.` will abort the search and return to the prompt.
+Loading a Prolog file is also called “consulting” it. The built-in
+predicate `consult/1` can be used to consult a file from within
+Prolog:
 
-Wildcards work as well:
+```
+?- consult('program.pl').
+```
+
+As an abbreviation for `consult/1`, you can specify a *list* of
+program files, given as *atoms*:
+
+```
+?- ['program.pl'].
+```
+
+The special notation `[user]` is used to read Prolog&nbsp;text from
+standard input. For example,
 
 ```
 ?- [user].
-(type Enter + Ctrl-D to terminate the stream when finished)
-member(X, [X|_]).
-member(X, [_|Xs]) :- member(X, Xs).
-?- member(X, [a, b, c]).
-true .
-X = a ;
-X = b ;
-X = c ;
-false.
-```
-and so do conjunctive queries:
-```
-?- [user].
-(type Enter + Ctrl-D to terminate the stream when finished)
-f(X) :- g(X).
-g(x). g(y). g(z).
-h(call(f, X)).
-?- h(X), X.
-true .
-X = call(f, x) ;
-X = call(f, y) ;
-X = call(f, z).
+hello(declarative_world).
+hello(pure_world).
 ```
 
-Note that the values of variables belonging to successful queries are
-printed out, on one line each. Uninstantiated variables are denoted by
-a number preceded by an underscore (`X = _0` in an example above).
+Pressing `RETURN` followed by `Ctrl-d` stops reading from
+standard&nbsp;input and consults the entered Prolog&nbsp;text.
+
+After a program is consulted, you can ask *queries* about the
+predicates it defines. For example, with the program shown above:
 
-To clear the database, type
 ```
-?- [clear].
+?- hello(What).
+   What = declarative_world
+;  What = pure_world.
 ```
 
-To quit scryer-prolog, type
+Press `SPACE` to show further answers, if any exist. Press `RETURN` or
+&nbsp;`.` to abort the search and return to the toplevel&nbsp;prompt.
+Press&nbsp;`h` to show a help message.
+
+To quit Scryer Prolog, use the standard predicate `halt/0`:
+
 ```
 ?- halt.
 ```
@@ -301,42 +219,247 @@ Scryer supports dynamic operators. Using the built-in
 arithmetic operators with the usual precedences,
 
 ```
-?- write_canonical(-5 + 3 - (2 * 4) // 8).
--(+(-(5), 3), //(*(2, 4), 8))
-true.
+?- write_canonical(-5 + 3 - (2 * 4) // 8), nl.
+-(+(-5,3),//(*(2,4),8))
+   true.
 ```
 
 New operators can be defined using the `op` declaration.
 
-### Partial strings
+### Strings and partial strings
 
-Scryer has two specialized, non-ISO builtin predicates for handling
-so-called "partial strings". Partial strings imitate difference lists
-of characters, but are much more space efficient. This efficiency
-comes at the cost of full generality -- you cannot unify the tail
-variables of two distinct partial strings, because their buffers will
-always be distinct.
+In Scryer Prolog, the default value of the Prolog flag `double_quotes`
+is `chars`, which is also the recommended setting. This means that
+double-quoted strings are interpreted as lists of *characters*, in the
+tradition of Marseille&nbsp;Prolog.
 
-If `X` is a free variable, the query
+For example, the following query succeeds:
 
-`?- partial_string("abc", X), X = [a, b, c | Y], is_partial_string(X),
-is_partial_string(Y).`
+```
+?- "abc" = [a,b,c].
+   true.
+```
 
-will succeed. Further, if `Y` a free variable, unifying `Y` against
-another string, "def" in this case, produces the equations
+Internally, strings are represented very compactly in packed
+UTF-8&nbsp;encoding. A naive representation of strings as lists of
+characters would use one memory&nbsp;cell per character, one
+memory&nbsp;cell per list constructor, and one memory&nbsp;cell for
+each tail that occurs in the list. Since one memory&nbsp;cell takes
+8&nbsp;bytes on 64-bit machines, the packed representation used by
+Scryer&nbsp;Prolog yields an up&nbsp;to **24-fold&nbsp;reduction** of
+memory usage, and corresponding reduction of memory&nbsp;accesses when
+creating and processing strings.
 
-`X = [a, b, c, d, e, f], Y = [d, e, f].`
+Scryer Prolog uses the same efficient encoding for *partial* strings,
+which appear to Prolog code as partial lists of characters. The
+predicate `partial_string/3` from `library(iso_ext)` lets you
+construct partial&nbsp;strings explicitly. For example:
+
+```
+?- partial_string("abc", Ls0, Ls).
+   Ls0 = [a,b,c|Ls].
+```
+
+In this case, and as the answer illustrates, `Ls0` is
+indistinguishable from a partial&nbsp;list with tail&nbsp;`Ls`, while
+the efficient packed representation is used internally.
+
+An important design goal of Scryer Prolog is to *automatically* use
+the efficient string representation whenever possible. Therefore, it
+is only very rarely necessary to use `partial_string/3` explicitly. In
+the above example, posting <tt>Ls0&nbsp;=&nbsp;[a,b,c|Ls]</tt> yields
+the exact same internal representation, and has the advantage that
+only the standard predicate&nbsp;`(=)/2` is used.
+
+Definite clause grammars as provided by
+[`library(dcgs)`](src/lib/lists.pl), and the predicates from
+[`library(lists)`](src/lib/lists.pl), are ideally suited for reasoning
+about strings.
+
+Partial strings were first proposed by Ulrich Neumerkel in issue
+[#95](https://github.com/mthom/scryer-prolog/issues/95).
+
+### Tabling (SLG resolution)
+
+One of the foremost attractions of Prolog is that logical consequences
+of pure&nbsp;programs can be derived by various execution strategies
+that differ regarding essential properties such as termination,
+completeness and efficiency.
+
+The default execution strategy of Prolog is depth-first search with
+chronological backtracking. This strategy is very efficient. Its main
+drawback is that it is *incomplete*: It may fail to find any solution
+even if one exists.
+
+Scryer Prolog supports an alternative execution strategy which is
+called *tabling* and also known as tabled&nbsp;execution and
+SLG&nbsp;resolution. To enable tabled execution for a predicate, use
+[`library(tabling)`](src/lib/tabling.pl) and add a `(table)/1`
+directive for the desired predicate indicator. For example, if we
+write:
+
+```
+:- use_module(library(tabling)).
+:- table a/0.
+
+a :- a.
+```
+
+Then the query `?- a.` *terminates* (and fails), whereas it
+does&nbsp;not terminate with the default execution strategy.
+
+Scryer Prolog implements tabling via *delimited continuations* as
+described in [*Tabling as a Library with Delimited
+Control*](https://biblio.ugent.be/publication/6880648/file/6885145.pdf)
+by Desouter&nbsp;et.&nbsp;al.
+
+### Constraint Logic Programming (CLP)
+
+Scryer Prolog provides excellent support for Constraint Logic
+Programming&nbsp;(CLP), which is the amalgamation of
+Logic&nbsp;Programming&nbsp;(LP) and Constraints.
+
+In addition to built-in support for [`dif/2`](src/lib/dif.pl),
+[`freeze/2`](src/lib/freeze.pl),
+[CLP(B)](src/lib/clpb.pl) and [CLP(ℤ)](src/lib/clpz.pl),
+Scryer provides a convenient way to implement new user-defined
+constraints: *Attributed variables* are available via
+[`library(atts)`](src/lib/atts.pl) as in SICStus&nbsp;Prolog,
+which is one of the most sophisticated and fastest constraint systems
+in existence. In [`library(iso_ext)`](src/lib/iso_ext.pl),
+Scryer provides predicates for backtrackable (`bb_b_put/2`) and
+non-backtrackable (`bb_put/2`) global variables, which are needed to
+implement certain types of constraint&nbsp;solvers.
+
+These features make Scryer Prolog an ideal platform for teaching,
+learning and developing portable CLP&nbsp;applications.
 
 ### Modules
 
 Scryer has a simple predicate-based module system. It provides a
 way to separate units of code into distinct namespaces, for both
-predicates and operators. See the files `src/prolog/lib/*.pl` for
+predicates and operators. See the files
+[`src/lib/*.pl`](src/lib) for
 examples.
 
-At the time of this writing, several control and list processing
-operators and predicates are hidden in their own modules that have not
-been exported to the toplevel. To export them, write
+At the time of this writing, many predicates reside in their own
+modules that need to be imported before they can be used.
+The modules that ship with Scryer&nbsp;Prolog are also called
+*library*&nbsp;modules or *libraries*, and include:
+
+* [`lists`](src/lib/lists.pl)
+  providing `length/2`, `member/2`, `select/3`, `append/[2,3]`,
+  `foldl/[4,5]`, `maplist/[2-9]`, `same_length/2`, `transpose/2` etc.
+* [`dcgs`](src/lib/dcgs.pl)
+  Definite Clause Grammars (DCGs), a built-in grammar mechanism
+  that uses the operator `(-->)/2` to define grammar rules,
+  and the predicates `phrase/[2,3]` to invoke them.
+* [`dif`](src/lib/dif.pl)
+  The predicate `dif/2` provides declarative disequality:
+  It is true if and only if its arguments are different, and
+  delays the test until a sound decision can be made.
+* [`reif`](src/lib/reif.pl)
+  providing `if_/3`, `tfilter/3` and related predicates
+  as described in *Indexing&nbsp;dif/2*.
+* [`clpz`](src/lib/clpz.pl)
+  CLP(ℤ): Constraint Logic Programming over Integers,
+  providing declarative integer arithmetic via `(#=)/2`, `(#\=)/2`,
+  `(#>=)/2` etc., and various global constraints and
+  enumeration predicates for solving combinatorial tasks.
+* [`pairs`](src/lib/pairs.pl)
+  By convention, *pairs* are Prolog terms with
+  principal&nbsp;functor `(-)/2`, written as `Key-Value`.
+  This library provides `pairs_keys_values/3`,
+  `pairs_keys/2`, and other predicates to reason about pairs.
+* [`si`](src/lib/si.pl)
+  The predicates `atom_si/1`, `integer_si/1`, `atomic_si/1`
+  and `list_si/1` implement sound type checks. They raise
+  instantiation errors if no decision can be made.
+  They are declarative replacements for logically flawed
+  lower-level type tests. For instance, instead of `integer(X)`,
+  write `integer_si(X)` to ensure soundness of your programs.
+  "si" stands for *sufficiently instantiated*, and also for
+  *sound&nbsp;inference*.
+* [`debug`](src/lib/debug.pl)
+  Various predicates that allow for declarative debugging.
+* [`pio`](src/lib/pio.pl)
+  `phrase_from_file/2` applies a DCG nonterminal to the contents of a
+  file, reading lazily only as much as is needed. Due to the compact
+  internal string representation, also extremely large files can be
+  efficiently processed with Scryer&nbsp;Prolog in this way.
+* [`charsio`](src/lib/charsio.pl) Various predicates that are useful
+  for parsing and reasoning about characters, notably `char_type/2` to
+  classify characters according to their type, and conversion
+  predicates for different encodings of strings.
+* [`error`](src/lib/error.pl)
+  `must_be/2` and `can_be/2` complement the type checks provided by
+  [`library(si)`](src/lib/si.pl), and are especially useful for
+  Prolog library authors.
+* [`tabling`](src/lib/tabling.pl)
+  The operator `(table)/1` is used in directives that prepare
+  predicates for tabled execution (SLG&nbsp;resolution).
+* [`format`](src/lib/format.pl)
+  The nonterminal `format_//2` is used to describe formatted output,
+  arranging arguments according to a given format&nbsp;string.
+  The predicates `format/[2,3]`, `portray_clause/[1,2]` and `listing/1`
+  provide formatted *impure* output.
+* [`assoc`](src/lib/assoc.pl)
+  providing `empty_assoc/1`, `get_assoc/3`, `put_assoc/4` etc.
+  to manage elements in AVL&nbsp;trees which ensure
+  *O*(log(*N*))&nbsp;access.
+* [`ordsets`](src/lib/ordsets.pl)
+  represents ordered sets as lists.
+* [`clpb`](src/lib/clpb.pl)
+  CLP(B): Constraint Logic Programming over Boolean variables,
+  a BDD-based SAT&nbsp;solver provided via the predicates
+  `sat/1`, `taut/2`, `labeling/1` etc.
+* [`arithmetic`](src/lib/arithmetic.pl)
+  Arithmetic predicates such as `lsb/2`, `msb/2` and
+  `number_to_rational/2`.
+* [`time`](src/lib/time.pl) Predicates for reasoning about
+  time, including `time/1` to measure the CPU&nbsp;time of a goal,
+  `current_time/1` to obtain the current system time, the nonterminal
+  `format_time//2` to describe strings with dates and times, and
+  `sleep/1` to slow down a computation.
+* [`files`](src/lib/files.pl)
+  Predicates for reasoning about files and directories, such as
+  `directory_files/2`, `file_exists/1` and `file_size/2`.
+* [`cont`](src/lib/cont.pl)
+  Provides *delimited continuations* via `reset/3` and `shift/1`.
+* [`random`](src/lib/random.pl)
+  Probabilistic predicates and random number generators.
+* [`http/http_open`](src/lib/http/http_open.pl) Open a stream to
+  read answers from web&nbsp;servers. HTTPS is also supported.
+* [`sgml`](src/lib/sgml.pl)
+  `load_html/3` and `load_xml/3` represent HTML and XML&nbsp;documents
+  as Prolog&nbsp;terms for convenient and efficient reasoning. Use
+  [`library(xpath)`](src/lib/iso_ext.pl) to extract information from
+  parsed documents.
+* [`csv`](src/lib/csv.pl)
+  `parse_csv//1` and `parse_csv//2` can be used with [`phrase_from_file/2`](src/lib/pio.pl)
+  or [`phrase/2`](src/lib/dcgs.pl) to parse csv
+* [`xpath`](src/lib/xpath.pl)
+  The predicate `xpath/3` is used for convenient reasoning about HTML
+  and XML&nbsp;documents, inspired by the XPath language. This library
+  is often used together with [`library(sgml)`](src/lib/sgml.pl).
+* [`sockets`](src/lib/sockets.pl)
+  Predicates for opening and accepting TCP connections as streams.
+  TLS negotiation is performed via the option `tls(true)` in
+  `socket_client_open/3`, yielding secure encrypted connections.
+* [`os`](src/lib/os.pl)
+  Predicates for reasoning about environment&nbsp;variables.
+* [`iso_ext`](src/lib/iso_ext.pl)
+  Conforming extensions to and candidates for inclusion in the Prolog
+  ISO&nbsp;standard, such as `setup_call_cleanup/3` and
+  `call_with_inference_limit/3`.
+* [`crypto`](src/lib/crypto.pl)
+  Cryptographically secure random numbers and hashes, HMAC-based key
+  derivation&nbsp;(HKDF), password-based key derivation&nbsp;(PBKDF2),
+  public key signatures and signature verification with&nbsp;Ed25519,
+  ECDH key&nbsp;exchange over Curve25519 (X25519), authenticated symmetric
+  encryption with ChaCha20-Poly1305, and reasoning about elliptic curves.
+
+To use predicates provided by the `lists` library, write:
 
 ```
 ?- use_module(library(lists)).
@@ -371,7 +494,6 @@ REPL:
 
 ```
 ?- [user].
-(type Enter + Ctrl-D to terminate the stream when finished)
 :- module(test, [local_member/2]).
 :- use_module(library(lists)).
 
@@ -379,4 +501,18 @@ local_member(X, Xs) :- member(X, Xs).
 ```
 
 The user listing can also be terminated by placing `end_of_file.` at
-the end of the stream.
+the end of the stream.
+
+### Configuration file
+
+At startup, Scryer Prolog consults the file `~/.scryerrc`, if the file
+exists. This file is useful to automatically load libraries and define
+predicates that you need often.
+
+For example, a sensible starting point for `~/.scryerrc` is:
+
+```
+:- use_module(library(lists)).
+:- use_module(library(dcgs)).
+:- use_module(library(reif)).
+```

build.rs

@@ -1,56 +1,55 @@
 extern crate indexmap;
 
-use indexmap::IndexSet;
-
 use std::env;
-use std::fs::{File, copy, read_dir};
+use std::fs;
+use std::fs::File;
 use std::io::Write;
 use std::path::Path;
 
-fn main()
-{
+fn find_prolog_files(libraries: &mut File, prefix: &str, current_dir: &Path) {
+    let entries = match current_dir.read_dir() {
+        Ok(entries) => entries,
+        Err(_) => return,
+    };
+    for entry in entries.filter_map(Result::ok).map(|e| e.path()) {
+        if entry.is_dir() {
+            if let Some(file_name) = entry.file_name() {
+                let new_prefix =
+                    prefix.to_owned() + file_name.to_str().unwrap() + "/";
+                find_prolog_files(libraries, &new_prefix, &entry);
+            }
+        } else if entry.is_file() {
+            let ext = std::ffi::OsStr::new("pl");
+            if entry.extension() == Some(ext) {
+                let contain =
+                    String::from_utf8(fs::read(&entry).unwrap()).unwrap();
+                let name = entry.file_stem().unwrap().to_str().unwrap();
+                let line = format!(
+                    "        m.insert(\"{}\",\n{:?});\n",
+                    prefix.to_owned() + name,
+                    contain
+                );
+
+                libraries.write_all(line.as_bytes()).unwrap();
+            }
+        }
+    }
+}
+
+fn main() {
     let out_dir = env::var("OUT_DIR").unwrap();
     let dest_path = Path::new(&out_dir).join("libraries.rs");
 
     let mut libraries = File::create(&dest_path).unwrap();
-    let mut library_index = IndexSet::new();
+    let lib_path = Path::new("src/lib");
 
-    let paths = read_dir("./src/prolog/lib").unwrap();
-
-    for item in paths {
-        let item = item.unwrap().path();
-
-        if let Some(file_name) = item.file_name() {
-            if let Some(ext) = item.extension() {
-                if ext == "pl" {
-                    let file_stem = item.file_stem().unwrap();
-                    let file_str  = file_stem.to_string_lossy().to_uppercase();
-                    let dest = Path::new(&out_dir).join(file_name);
-
-                    match copy(&item, dest) {
-                        Ok(_) => {},
-                        Err(e) => panic!("die: {:?}", e)
-                    };
-
-                    let include_line = format!("static {}: &str = include_str!(\"{}.pl\");\n",
-                                               file_str, file_stem.to_string_lossy());
-
-                    libraries.write_all(include_line.as_bytes()).unwrap();
-                    library_index.insert(file_stem.to_string_lossy().to_string());
-                }
-            }
-        }
-    }
-
-    libraries.write_all(b"\nref_thread_local! {
+    libraries
+        .write_all(
+            b"ref_thread_local! {
     pub static managed LIBRARIES: IndexMap<&'static str, &'static str> = {
-        let mut m = IndexMap::new();\n").unwrap();
-
-    for item in library_index {
-        let line = format!("\n        m.insert(\"{}\", {});", item, item.to_uppercase());
-        libraries.write_all(line.as_bytes()).unwrap();
-    }
-
-    libraries.write_all(b"\n\n        m\n    };
-}").unwrap();
+        let mut m = IndexMap::new();\n",
+        )
+        .unwrap();
+    find_prolog_files(&mut libraries, "", &lib_path);
+    libraries.write_all(b"\n        m\n    };\n}\n").unwrap();
 }

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+<path d="M0 285 h 300 v 15 h -300 z"/>
+<path d="M0 0 v 300 h 15 v -300 z"/>
+<path d="M285 0 v 300 h 15 v -300 z"/>
+</svg>

src/allocator.rs

@@ -1,9 +1,9 @@
-use prolog_parser::ast::*;
+use crate::prolog_parser::ast::*;
 
-use crate::prolog::fixtures::*;
-use crate::prolog::forms::*;
-use crate::prolog::machine::machine_indices::*;
-use crate::prolog::targets::*;
+use crate::fixtures::*;
+use crate::forms::*;
+use crate::machine::machine_indices::*;
+use crate::targets::*;
 
 use std::cell::Cell;
 use std::rc::Rc;

src/arithmetic.rs

@@ -1,26 +1,29 @@
-use prolog_parser::ast::*;
+use crate::prolog_parser::ast::*;
 
-use crate::prolog::clause_types::*;
-use crate::prolog::fixtures::*;
-use crate::prolog::forms::*;
-use crate::prolog::instructions::*;
-use crate::prolog::iterators::*;
+use crate::clause_types::*;
+use crate::fixtures::*;
+use crate::forms::*;
+use crate::instructions::*;
+use crate::iterators::*;
 
-use crate::prolog::machine::machine_errors::*;
-use crate::prolog::machine::machine_indices::*;
+use crate::machine::heap::*;
+use crate::machine::machine_errors::*;
+use crate::machine::machine_indices::*;
 
-use crate::prolog::ordered_float::*;
-use crate::prolog::rug::ops::PowAssign;
-use crate::prolog::rug::{Assign, Integer, Rational};
+use crate::ordered_float::*;
+use crate::rug::ops::PowAssign;
+use crate::rug::{Assign, Integer, Rational};
 
 use std::cell::Cell;
 use std::cmp::{max, min, Ordering};
+use std::convert::TryFrom;
 use std::f64;
 use std::num::FpCategory;
 use std::ops::{Add, Div, Mul, Neg, Sub};
 use std::rc::Rc;
 use std::vec::Vec;
 
+#[derive(Debug)]
 pub struct ArithInstructionIterator<'a> {
     state_stack: Vec<TermIterState<'a>>,
 }
@@ -66,6 +69,7 @@ impl<'a> ArithInstructionIterator<'a> {
     }
 }
 
+#[derive(Debug)]
 pub enum ArithTermRef<'a> {
     Constant(&'a Constant),
     Op(ClauseName, usize), // name, arity.
@@ -107,6 +111,7 @@ impl<'a> Iterator for ArithInstructionIterator<'a> {
     }
 }
 
+#[derive(Debug)]
 pub struct ArithmeticEvaluator<'a> {
     bindings: &'a AllocVarDict,
     interm: Vec<ArithmeticTerm>,
@@ -159,6 +164,7 @@ impl<'a> ArithmeticEvaluator<'a> {
             "round" => Ok(ArithmeticInstruction::Round(a1, t)),
             "ceiling" => Ok(ArithmeticInstruction::Ceiling(a1, t)),
             "floor" => Ok(ArithmeticInstruction::Floor(a1, t)),
+            "sign" => Ok(ArithmeticInstruction::Sign(a1, t)),
             "\\" => Ok(ArithmeticInstruction::BitwiseComplement(a1, t)),
             _ => Err(ArithmeticError::NonEvaluableFunctor(
                 Constant::Atom(name, None),
@@ -192,6 +198,7 @@ impl<'a> ArithmeticEvaluator<'a> {
             "xor" => Ok(ArithmeticInstruction::Xor(a1, a2, t)),
             "mod" => Ok(ArithmeticInstruction::Mod(a1, a2, t)),
             "rem" => Ok(ArithmeticInstruction::Rem(a1, a2, t)),
+            "gcd" => Ok(ArithmeticInstruction::Gcd(a1, a2, t)),
             "atan2" => Ok(ArithmeticInstruction::ATan2(a1, a2, t)),
             _ => Err(ArithmeticError::NonEvaluableFunctor(
                 Constant::Atom(name, None),
@@ -260,6 +267,9 @@ impl<'a> ArithmeticEvaluator<'a> {
 
     fn push_constant(&mut self, c: &Constant) -> Result<(), ArithmeticError> {
         match c {
+            &Constant::Fixnum(n) => self
+                .interm
+                .push(ArithmeticTerm::Number(Number::Fixnum(n))),
             &Constant::Integer(ref n) => self
                 .interm
                 .push(ArithmeticTerm::Number(Number::Integer(n.clone()))),
@@ -314,18 +324,25 @@ impl<'a> ArithmeticEvaluator<'a> {
 }
 
 // integer division rounding function -- 9.1.3.1.
-pub fn rnd_i<'a>(n: &'a Number) -> RefOrOwned<'a, Integer> {
+pub fn rnd_i<'a>(n: &'a Number) -> RefOrOwned<'a, Number> {
     match n {
-        &Number::Integer(ref n) => RefOrOwned::Borrowed(n),
+        &Number::Integer(_) => {
+            RefOrOwned::Borrowed(n)
+        }
         &Number::Float(OrderedFloat(f)) => {
-            RefOrOwned::Owned(Integer::from_f64(f.floor()).unwrap_or_else(|| Integer::from(0)))
+            RefOrOwned::Owned(Number::from(
+                Integer::from_f64(f.floor()).unwrap_or_else(|| Integer::from(0))
+            ))
+        }
+        &Number::Fixnum(n) => {
+            RefOrOwned::Owned(Number::from(n))
         }
         &Number::Rational(ref r) => {
             let r_ref = r.fract_floor_ref();
             let (mut fract, mut floor) = (Rational::new(), Integer::new());
-
             (&mut fract, &mut floor).assign(r_ref);
-            RefOrOwned::Owned(floor)
+
+            RefOrOwned::Owned(Number::from(floor))
         }
     }
 }
@@ -333,6 +350,7 @@ pub fn rnd_i<'a>(n: &'a Number) -> RefOrOwned<'a, Integer> {
 // floating point rounding function -- 9.1.4.1.
 pub fn rnd_f(n: &Number) -> f64 {
     match n {
+        &Number::Fixnum(n) => n as f64,
         &Number::Integer(ref n) => n.to_f64(),
         &Number::Float(OrderedFloat(f)) => f,
         &Number::Rational(ref r) => r.to_f64(),
@@ -368,22 +386,32 @@ where
     }
 }
 
+#[inline]
+fn float_fn_to_f(n: isize) -> Result<f64, EvalError> {
+    classify_float(n as f64, rnd_f)
+}
+
+#[inline]
 fn float_i_to_f(n: &Integer) -> Result<f64, EvalError> {
     classify_float(n.to_f64(), rnd_f)
 }
 
+#[inline]
 fn float_r_to_f(r: &Rational) -> Result<f64, EvalError> {
     classify_float(r.to_f64(), rnd_f)
 }
 
+#[inline]
 fn add_f(f1: f64, f2: f64) -> Result<OrderedFloat<f64>, EvalError> {
     Ok(OrderedFloat(classify_float(f1 + f2, rnd_f)?))
 }
 
+#[inline]
 fn mul_f(f1: f64, f2: f64) -> Result<OrderedFloat<f64>, EvalError> {
     Ok(OrderedFloat(classify_float(f1 * f2, rnd_f)?))
 }
 
+#[inline]
 fn div_f(f1: f64, f2: f64) -> Result<OrderedFloat<f64>, EvalError> {
     if FpCategory::Zero == f2.classify() {
         Err(EvalError::ZeroDivisor)
@@ -397,23 +425,46 @@ impl Add<Number> for Number {
 
     fn add(self, rhs: Number) -> Self::Output {
         match (self, rhs) {
-            (Number::Integer(n1), Number::Integer(n2)) => Ok(Number::Integer(n1 + n2)), // add_i
+            (Number::Fixnum(n1), Number::Fixnum(n2)) => {
+                Ok(if let Some(result) = n1.checked_add(n2) {
+                    Number::Fixnum(result)
+                } else {
+                    Number::from(Integer::from(n1) + Integer::from(n2))
+                })
+            }
+            (Number::Fixnum(n1), Number::Integer(n2)) |
+            (Number::Integer(n2), Number::Fixnum(n1)) => {
+                Ok(Number::from(Integer::from(n1) + &*n2))
+            }
+            (Number::Fixnum(n1), Number::Rational(n2)) |
+            (Number::Rational(n2), Number::Fixnum(n1)) => {
+                Ok(Number::from(Rational::from(n1) + &*n2))
+            }
+            (Number::Fixnum(n1), Number::Float(OrderedFloat(n2))) |
+            (Number::Float(OrderedFloat(n2)), Number::Fixnum(n1)) => {
+                Ok(Number::Float(add_f(float_fn_to_f(n1)?, n2)?))
+            }
+            (Number::Integer(n1), Number::Integer(n2)) => {
+                Ok(Number::from(Integer::from(&*n1) + &*n2)) // add_i
+            }
             (Number::Integer(n1), Number::Float(OrderedFloat(n2)))
-            | (Number::Float(OrderedFloat(n2)), Number::Integer(n1)) => {
+          | (Number::Float(OrderedFloat(n2)), Number::Integer(n1)) => {
                 Ok(Number::Float(add_f(float_i_to_f(&n1)?, n2)?))
             }
             (Number::Integer(n1), Number::Rational(n2))
-            | (Number::Rational(n2), Number::Integer(n1)) => {
-                Ok(Number::Rational(Rational::from(n1) + n2))
+          | (Number::Rational(n2), Number::Integer(n1)) => {
+                Ok(Number::from(Rational::from(&*n1) + &*n2))
             }
             (Number::Rational(n1), Number::Float(OrderedFloat(n2)))
-            | (Number::Float(OrderedFloat(n2)), Number::Rational(n1)) => {
+          | (Number::Float(OrderedFloat(n2)), Number::Rational(n1)) => {
                 Ok(Number::Float(add_f(float_r_to_f(&n1)?, n2)?))
             }
             (Number::Float(OrderedFloat(f1)), Number::Float(OrderedFloat(f2))) => {
                 Ok(Number::Float(add_f(f1, f2)?))
             }
-            (Number::Rational(r1), Number::Rational(r2)) => Ok(Number::Rational(r1 + r2)),
+            (Number::Rational(r1), Number::Rational(r2)) => {
+                Ok(Number::from(Rational::from(&*r1) + &*r2))
+            }
         }
     }
 }
@@ -423,9 +474,15 @@ impl Neg for Number {
 
     fn neg(self) -> Self::Output {
         match self {
-            Number::Integer(n) => Number::Integer(-n),
+            Number::Fixnum(n) =>
+                if let Some(n) = n.checked_neg() {
+                    Number::Fixnum(n)
+                } else {
+                    Number::from(-Integer::from(n))
+                }
+            Number::Integer(n) => Number::Integer(Rc::new(-Integer::from(&*n))),
             Number::Float(OrderedFloat(f)) => Number::Float(OrderedFloat(-f)),
-            Number::Rational(r) => Number::Rational(-r),
+            Number::Rational(r) => Number::Rational(Rc::new(-Rational::from(&*r))),
         }
     }
 }
@@ -443,14 +500,35 @@ impl Mul<Number> for Number {
 
     fn mul(self, rhs: Number) -> Self::Output {
         match (self, rhs) {
-            (Number::Integer(n1), Number::Integer(n2)) => Ok(Number::Integer(n1 * n2)), // mul_i
+            (Number::Fixnum(n1), Number::Fixnum(n2)) => {
+                Ok(if let Some(result) = n1.checked_mul(n2) {
+                    Number::Fixnum(result)
+                } else {
+                    Number::from(Integer::from(n1) * Integer::from(n2))
+                })
+            }
+            (Number::Fixnum(n1), Number::Integer(n2)) |
+            (Number::Integer(n2), Number::Fixnum(n1)) => {
+                Ok(Number::from(Integer::from(n1) * &*n2))
+            }
+            (Number::Fixnum(n1), Number::Rational(n2)) |
+            (Number::Rational(n2), Number::Fixnum(n1)) => {
+                Ok(Number::from(Rational::from(n1) * &*n2))
+            }
+            (Number::Fixnum(n1), Number::Float(OrderedFloat(n2))) |
+            (Number::Float(OrderedFloat(n2)), Number::Fixnum(n1)) => {
+                Ok(Number::Float(mul_f(float_fn_to_f(n1)?, n2)?))
+            }
+            (Number::Integer(n1), Number::Integer(n2)) => {
+                Ok(Number::Integer(Rc::new(Integer::from(&*n1) * &*n2))) // mul_i
+            }
             (Number::Integer(n1), Number::Float(OrderedFloat(n2)))
             | (Number::Float(OrderedFloat(n2)), Number::Integer(n1)) => {
                 Ok(Number::Float(mul_f(float_i_to_f(&n1)?, n2)?))
             }
             (Number::Integer(n1), Number::Rational(n2))
             | (Number::Rational(n2), Number::Integer(n1)) => {
-                Ok(Number::Rational(Rational::from(n1) * n2))
+                Ok(Number::Rational(Rc::new(Rational::from(&*n1) * &*n2)))
             }
             (Number::Rational(n1), Number::Float(OrderedFloat(n2)))
             | (Number::Float(OrderedFloat(n2)), Number::Rational(n1)) => {
@@ -459,7 +537,9 @@ impl Mul<Number> for Number {
             (Number::Float(OrderedFloat(f1)), Number::Float(OrderedFloat(f2))) => {
                 Ok(Number::Float(mul_f(f1, f2)?))
             }
-            (Number::Rational(r1), Number::Rational(r2)) => Ok(Number::Rational(r1 * r2)),
+            (Number::Rational(r1), Number::Rational(r2)) => {
+                Ok(Number::Rational(Rc::new(Rational::from(&*r1) * &*r2)))
+            }
         }
     }
 }
@@ -469,24 +549,72 @@ impl Div<Number> for Number {
 
     fn div(self, rhs: Number) -> Self::Output {
         match (self, rhs) {
-            (Number::Integer(n1), Number::Integer(n2)) => Ok(Number::Float(div_f(
-                float_i_to_f(&n1)?,
-                float_i_to_f(&n2)?,
-            )?)),
+            (Number::Fixnum(n1), Number::Fixnum(n2)) => {
+                Ok(Number::Float(div_f(
+                    float_fn_to_f(n1)?,
+                    float_fn_to_f(n2)?,
+                )?))
+            }
+            (Number::Fixnum(n1), Number::Integer(n2)) => {
+                Ok(Number::Float(div_f(
+                    float_fn_to_f(n1)?,
+                    float_i_to_f(&n2)?,
+                )?))
+            }
+            (Number::Integer(n1), Number::Fixnum(n2)) => {
+                Ok(Number::Float(div_f(
+                    float_i_to_f(&n1)?,
+                    float_fn_to_f(n2)?,
+                )?))
+            }
+            (Number::Fixnum(n1), Number::Rational(n2)) => {
+                Ok(Number::Float(div_f(
+                    float_fn_to_f(n1)?,
+                    float_r_to_f(&n2)?,
+                )?))
+            }
+            (Number::Rational(n1), Number::Fixnum(n2)) => {
+                Ok(Number::Float(div_f(
+                    float_r_to_f(&n1)?,
+                    float_fn_to_f(n2)?,
+                )?))
+            }
+            (Number::Fixnum(n1), Number::Float(OrderedFloat(n2))) => {
+                Ok(Number::Float(div_f(
+                    float_fn_to_f(n1)?,
+                    n2,
+                )?))
+            }
+            (Number::Float(OrderedFloat(n1)), Number::Fixnum(n2)) => {
+                Ok(Number::Float(div_f(
+                    n1,
+                    float_fn_to_f(n2)?,
+                )?))
+            }
+            (Number::Integer(n1), Number::Integer(n2)) => {
+                Ok(Number::Float(div_f(
+                    float_i_to_f(&n1)?,
+                    float_i_to_f(&n2)?,
+                )?))
+            }
             (Number::Integer(n1), Number::Float(OrderedFloat(n2))) => {
                 Ok(Number::Float(div_f(float_i_to_f(&n1)?, n2)?))
             }
             (Number::Float(OrderedFloat(n2)), Number::Integer(n1)) => {
                 Ok(Number::Float(div_f(n2, float_i_to_f(&n1)?)?))
             }
-            (Number::Integer(n1), Number::Rational(n2)) => Ok(Number::Float(div_f(
-                float_i_to_f(&n1)?,
-                float_r_to_f(&n2)?,
-            )?)),
-            (Number::Rational(n2), Number::Integer(n1)) => Ok(Number::Float(div_f(
-                float_r_to_f(&n2)?,
-                float_i_to_f(&n1)?,
-            )?)),
+            (Number::Integer(n1), Number::Rational(n2)) => {
+                Ok(Number::Float(div_f(
+                    float_i_to_f(&n1)?,
+                    float_r_to_f(&n2)?,
+                )?))
+            }
+            (Number::Rational(n2), Number::Integer(n1)) => {
+                Ok(Number::Float(div_f(
+                    float_r_to_f(&n2)?,
+                    float_i_to_f(&n1)?,
+                )?))
+            }
             (Number::Rational(n1), Number::Float(OrderedFloat(n2))) => {
                 Ok(Number::Float(div_f(float_r_to_f(&n1)?, n2)?))
             }
@@ -504,41 +632,172 @@ impl Div<Number> for Number {
     }
 }
 
+impl PartialEq for Number {
+    fn eq(&self, rhs: &Self) -> bool {
+        match (self, rhs) {
+            (&Number::Fixnum(n1), &Number::Fixnum(n2)) => n1.eq(&n2),
+            (&Number::Fixnum(n1), &Number::Integer(ref n2)) => n1.eq(&**n2),
+            (&Number::Integer(ref n1), &Number::Fixnum(n2)) => (&**n1).eq(&n2),
+            (&Number::Fixnum(n1), &Number::Rational(ref n2)) => n1.eq(&**n2),
+            (&Number::Rational(ref n1), &Number::Fixnum(n2)) => (&**n1).eq(&n2),
+            (&Number::Fixnum(n1), &Number::Float(n2)) => OrderedFloat(n1 as f64).eq(&n2),
+            (&Number::Float(n1), &Number::Fixnum(n2)) => n1.eq(&OrderedFloat(n2 as f64)),
+            (&Number::Integer(ref n1), &Number::Integer(ref n2)) => n1.eq(n2),
+            (&Number::Integer(ref n1), Number::Float(n2)) => OrderedFloat(n1.to_f64()).eq(&n2),
+            (&Number::Float(n1), &Number::Integer(ref n2)) => n1.eq(&OrderedFloat(n2.to_f64())),
+            (&Number::Integer(ref n1), &Number::Rational(ref n2)) => {
+                #[cfg(feature = "num")]
+                {
+                    &Rational::from(&**n1) == &**n2
+                }
+                #[cfg(not(feature = "num"))]
+                {
+                    &**n1 == &**n2
+                }
+            }
+            (&Number::Rational(ref n1), &Number::Integer(ref n2)) => {
+                #[cfg(feature = "num")]
+                {
+                    &**n1 == &Rational::from(&**n2)
+                }
+                #[cfg(not(feature = "num"))]
+                {
+                    &**n1 == &**n2
+                }
+            }
+            (&Number::Rational(ref n1), &Number::Float(n2)) => OrderedFloat(n1.to_f64()).eq(&n2),
+            (&Number::Float(n1), &Number::Rational(ref n2)) => n1.eq(&OrderedFloat(n2.to_f64())),
+            (&Number::Float(f1), &Number::Float(f2)) => f1.eq(&f2),
+            (&Number::Rational(ref r1), &Number::Rational(ref r2)) => r1.eq(&r2),
+        }
+    }
+}
+
+impl Eq for Number {}
+
 impl PartialOrd for Number {
     fn partial_cmp(&self, rhs: &Number) -> Option<Ordering> {
-        match (self, rhs) {
-            (&Number::Integer(ref n1), &Number::Integer(ref n2)) => Some(n1.cmp(n2)),
-            (&Number::Integer(_), Number::Float(_)) => Some(Ordering::Greater),
-            (&Number::Float(_), &Number::Integer(_)) => Some(Ordering::Less),
-            (&Number::Integer(_), &Number::Rational(_)) => Some(Ordering::Greater),
-            (&Number::Rational(_), &Number::Integer(_)) => Some(Ordering::Less),
-            (&Number::Rational(_), Number::Float(_)) => Some(Ordering::Greater),
-            (&Number::Float(_), &Number::Rational(_)) => Some(Ordering::Less),
-            (&Number::Float(f1), &Number::Float(f2)) => Some(f1.cmp(&f2)),
-            (&Number::Rational(ref r1), &Number::Rational(ref r2)) => Some(r1.cmp(&r2)),
-        }
+        Some(self.cmp(rhs))
     }
 }
 
 impl Ord for Number {
     fn cmp(&self, rhs: &Number) -> Ordering {
         match (self, rhs) {
+            (&Number::Fixnum(n1), &Number::Fixnum(n2)) => n1.cmp(&n2),
+            (&Number::Fixnum(n1), Number::Integer(n2)) => Integer::from(n1).cmp(&*n2),
+            (Number::Integer(n1), &Number::Fixnum(n2)) => (&**n1).cmp(&Integer::from(n2)),
+            (&Number::Fixnum(n1), Number::Rational(n2)) => Rational::from(n1).cmp(&*n2),
+            (Number::Rational(n1), &Number::Fixnum(n2)) => (&**n1).cmp(&Rational::from(n2)),
+            (&Number::Fixnum(n1), &Number::Float(n2)) => OrderedFloat(n1 as f64).cmp(&n2),
+            (&Number::Float(n1), &Number::Fixnum(n2)) => n1.cmp(&OrderedFloat(n2 as f64)),
             (&Number::Integer(ref n1), &Number::Integer(ref n2)) => n1.cmp(n2),
-            (&Number::Integer(_), Number::Float(_)) => Ordering::Greater,
-            (&Number::Float(_), &Number::Integer(_)) => Ordering::Less,
-            (&Number::Integer(_), &Number::Rational(_)) => Ordering::Greater,
-            (&Number::Rational(_), &Number::Integer(_)) => Ordering::Less,
-            (&Number::Rational(_), Number::Float(_)) => Ordering::Greater,
-            (&Number::Float(_), &Number::Rational(_)) => Ordering::Less,
+            (&Number::Integer(ref n1), Number::Float(n2)) => OrderedFloat(n1.to_f64()).cmp(&n2),
+            (&Number::Float(n1), &Number::Integer(ref n2)) => n1.cmp(&OrderedFloat(n2.to_f64())),
+            (&Number::Integer(ref n1), &Number::Rational(ref n2)) => {
+                #[cfg(feature = "num")]
+                {
+                    Rational::from(&**n1).cmp(n2)
+                }
+                #[cfg(not(feature = "num"))]
+                {
+                    (&**n1).partial_cmp(&**n2).unwrap_or(Ordering::Less)
+                }
+            }
+            (&Number::Rational(ref n1), &Number::Integer(ref n2)) => {
+                #[cfg(feature = "num")]
+                {
+                    (&**n1).cmp(&Rational::from(&**n2))
+                }
+                #[cfg(not(feature = "num"))]
+                {
+                    (&**n1).partial_cmp(&**n2).unwrap_or(Ordering::Less)
+                }
+            }
+            (&Number::Rational(ref n1), &Number::Float(n2)) => OrderedFloat(n1.to_f64()).cmp(&n2),
+            (&Number::Float(n1), &Number::Rational(ref n2)) => n1.cmp(&OrderedFloat(n2.to_f64())),
             (&Number::Float(f1), &Number::Float(f2)) => f1.cmp(&f2),
             (&Number::Rational(ref r1), &Number::Rational(ref r2)) => r1.cmp(&r2),
         }
     }
 }
 
+impl<'a> TryFrom<(Addr, &'a Heap)> for Number {
+    type Error = ();
+
+    fn try_from((addr, heap): (Addr, &'a Heap)) -> Result<Number, Self::Error> {
+        match addr {
+            Addr::Fixnum(n) => {
+                Ok(Number::from(n))
+            }
+            Addr::Float(n) => {
+                Ok(Number::Float(n))
+            }
+            Addr::Usize(n) => {
+                if let Ok(n) = isize::try_from(n) {
+                    Ok(Number::from(n))
+                } else {
+                    Ok(Number::from(Integer::from(n)))
+                }
+            }
+            Addr::Con(h) => {
+                Number::try_from(&heap[h])
+            }
+            _ => {
+                Err(())
+            }
+        }
+    }
+}
+
+impl<'a> TryFrom<&'a HeapCellValue> for Number {
+    type Error = ();
+
+    fn try_from(value: &'a HeapCellValue) -> Result<Number, Self::Error> {
+        match value {
+            HeapCellValue::Addr(addr) => {
+                match addr {
+                    &Addr::Fixnum(n) => {
+                        Ok(Number::from(n))
+                    }
+                    &Addr::Float(n) => {
+                        Ok(Number::Float(n))
+                    }
+                    &Addr::Usize(n) => {
+                        if let Ok(n) = isize::try_from(n) {
+                            Ok(Number::from(n))
+                        } else {
+                            Ok(Number::from(Integer::from(n)))
+                        }
+                    }
+                    _ => {
+                        Err(())
+                    }
+                }
+            }
+            HeapCellValue::Integer(n) => {
+                Ok(Number::Integer(n.clone()))
+            }
+            HeapCellValue::Rational(n) => {
+                Ok(Number::Rational(n.clone()))
+            }
+            _ => {
+                Err(())
+            }
+        }
+    }
+}
+
+impl<'a> From<&'a Integer> for Number {
+    #[inline]
+    fn from(src: &'a Integer) -> Self {
+        Number::Integer(Rc::new(Integer::from(src)))
+    }
+}
+
 // Computes n ^ power. Ignores the sign of power.
-pub fn binary_pow(mut n: Integer, power: Integer) -> Integer {
-    let mut power = power.abs();
+pub fn binary_pow(mut n: Integer, power: &Integer) -> Integer {
+    let mut power = Integer::from(power.abs_ref());
 
     if power == 0 {
         return Integer::from(1);

src/clause_types.rs

@@ -1,13 +1,14 @@
-use prolog_parser::ast::*;
+use crate::prolog_parser::ast::*;
 
-use crate::prolog::forms::Number;
-use crate::prolog::machine::machine_indices::*;
+use crate::forms::Number;
+use crate::machine::machine_indices::*;
+use crate::rug::rand::RandState;
 
-use ref_thread_local::RefThreadLocal;
+use crate::ref_thread_local::RefThreadLocal;
 
 use std::collections::BTreeMap;
 
-#[derive(Clone, Copy, Eq, PartialEq)]
+#[derive(Debug, Clone, Copy, Eq, PartialEq)]
 pub enum CompareNumberQT {
     GreaterThan,
     LessThan,
@@ -30,7 +31,7 @@ impl CompareNumberQT {
     }
 }
 
-#[derive(Clone, Copy, PartialEq, Eq)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum CompareTermQT {
     LessThan,
     LessThanOrEqual,
@@ -49,7 +50,7 @@ impl CompareTermQT {
     }
 }
 
-#[derive(Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq)]
 pub enum ArithmeticTerm {
     Reg(RegType),
     Interm(usize),
@@ -66,7 +67,7 @@ impl ArithmeticTerm {
     }
 }
 
-#[derive(Clone, Eq, PartialEq)]
+#[derive(Debug, Clone, Eq, PartialEq)]
 pub enum InlinedClauseType {
     CompareNumber(CompareNumberQT, ArithmeticTerm, ArithmeticTerm),
     IsAtom(RegType),
@@ -74,13 +75,15 @@ pub enum InlinedClauseType {
     IsCompound(RegType),
     IsInteger(RegType),
     IsRational(RegType),
-    IsString(RegType),
     IsFloat(RegType),
     IsNonVar(RegType),
-    IsPartialString(RegType),
     IsVar(RegType),
 }
 
+ref_thread_local! {
+    pub static managed RANDOM_STATE: RandState<'static> = RandState::new();
+}
+
 ref_thread_local! {
     pub static managed CLAUSE_TYPE_FORMS: BTreeMap<(&'static str, usize), ClauseType> = {
         let mut m = BTreeMap::new();
@@ -101,10 +104,8 @@ ref_thread_local! {
         m.insert(("compound", 1), ClauseType::Inlined(InlinedClauseType::IsCompound(r1)));
         m.insert(("integer", 1), ClauseType::Inlined(InlinedClauseType::IsInteger(r1)));
         m.insert(("rational", 1), ClauseType::Inlined(InlinedClauseType::IsRational(r1)));
-        m.insert(("string", 1), ClauseType::Inlined(InlinedClauseType::IsString(r1)));
         m.insert(("float", 1), ClauseType::Inlined(InlinedClauseType::IsFloat(r1)));
         m.insert(("nonvar", 1), ClauseType::Inlined(InlinedClauseType::IsNonVar(r1)));
-        m.insert(("is_partial_string", 1), ClauseType::Inlined(InlinedClauseType::IsPartialString(r1)));
         m.insert(("var", 1), ClauseType::Inlined(InlinedClauseType::IsVar(r1)));
         m.insert(("acyclic_term", 1), ClauseType::BuiltIn(BuiltInClauseType::AcyclicTerm));
         m.insert(("arg", 3), ClauseType::BuiltIn(BuiltInClauseType::Arg));
@@ -114,7 +115,6 @@ ref_thread_local! {
         m.insert(("@>=", 2), ClauseType::BuiltIn(BuiltInClauseType::CompareTerm(CompareTermQT::GreaterThanOrEqual)));
         m.insert(("@=<", 2), ClauseType::BuiltIn(BuiltInClauseType::CompareTerm(CompareTermQT::LessThanOrEqual)));
         m.insert(("copy_term", 2), ClauseType::BuiltIn(BuiltInClauseType::CopyTerm));
-        m.insert(("cyclic_term", 1), ClauseType::BuiltIn(BuiltInClauseType::CyclicTerm));
         m.insert(("==", 2), ClauseType::BuiltIn(BuiltInClauseType::Eq));
         m.insert(("functor", 3), ClauseType::BuiltIn(BuiltInClauseType::Functor));
         m.insert(("ground", 1), ClauseType::BuiltIn(BuiltInClauseType::Ground));
@@ -122,7 +122,6 @@ ref_thread_local! {
         m.insert(("keysort", 2), ClauseType::BuiltIn(BuiltInClauseType::KeySort));
         m.insert(("nl", 0), ClauseType::BuiltIn(BuiltInClauseType::Nl));
         m.insert(("\\==", 2), ClauseType::BuiltIn(BuiltInClauseType::NotEq));
-        m.insert(("partial_string", 2), ClauseType::BuiltIn(BuiltInClauseType::PartialString));
         m.insert(("read", 1), ClauseType::BuiltIn(BuiltInClauseType::Read));
         m.insert(("sort", 2), ClauseType::BuiltIn(BuiltInClauseType::Sort));
 
@@ -139,41 +138,66 @@ impl InlinedClauseType {
             &InlinedClauseType::IsCompound(..) => "compound",
             &InlinedClauseType::IsInteger(..) => "integer",
             &InlinedClauseType::IsRational(..) => "rational",
-            &InlinedClauseType::IsString(..) => "string",
             &InlinedClauseType::IsFloat(..) => "float",
             &InlinedClauseType::IsNonVar(..) => "nonvar",
-            &InlinedClauseType::IsPartialString(..) => "is_partial_string",
             &InlinedClauseType::IsVar(..) => "var",
         }
     }
 }
 
-#[derive(Copy, Clone, Eq, PartialEq)]
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
 pub enum SystemClauseType {
     AbolishClause,
     AbolishModuleClause,
     AssertDynamicPredicateToBack,
     AssertDynamicPredicateToFront,
+    AtEndOfExpansion,
     AtomChars,
     AtomCodes,
     AtomLength,
-    ModuleAssertDynamicPredicateToFront,
-    ModuleAssertDynamicPredicateToBack,
+    BindFromRegister,
+    CallContinuation,
     CharCode,
+    CharType,
     CharsToNumber,
+    ClearAttributeGoals,
+    CloneAttributeGoals,
     CodesToNumber,
+    CopyTermWithoutAttrVars,
     CheckCutPoint,
+    Close,
     CopyToLiftedHeap,
+    CreatePartialString,
+    CurrentHostname,
+    CurrentInput,
+    CurrentOutput,
+    DirectoryFiles,
+    FileSize,
+    FileExists,
+    DirectoryExists,
+    DirectorySeparator,
+    MakeDirectory,
+    DeleteFile,
+    WorkingDirectory,
+    PathCanonical,
+    FileTime,
     DeleteAttribute,
     DeleteHeadAttribute,
-    DynamicModuleResolution,
+    DynamicModuleResolution(usize),
     EnqueueAttributeGoal,
     EnqueueAttributedVar,
     ExpandGoal,
     ExpandTerm,
     FetchGlobalVar,
     FetchGlobalVarWithOffset,
+    FirstStream,
+    FlushOutput,
+    GetByte,
     GetChar,
+    GetNChars,
+    GetCode,
+    GetSingleChar,
+    ResetAttrVarState,
     TruncateIfNoLiftedHeapGrowthDiff,
     TruncateIfNoLiftedHeapGrowth,
     GetAttributedVariableList,
@@ -181,9 +205,11 @@ pub enum SystemClauseType {
     GetAttrVarQueueBeyond,
     GetBValue,
     GetClause,
+    GetContinuationChunk,
     GetModuleClause,
     GetNextDBRef,
     GetNextOpDBRef,
+    IsPartialString,
     LookupDBRef,
     LookupOpDBRef,
     Halt,
@@ -195,25 +221,45 @@ pub enum SystemClauseType {
     InstallSCCCleaner,
     InstallInferenceCounter,
     LiftedHeapLength,
+    ModuleAssertDynamicPredicateToFront,
+    ModuleAssertDynamicPredicateToBack,
+    ModuleExists,
     ModuleOf,
     ModuleRetractClause,
+    NextEP,
     NoSuchPredicate,
     NumberToChars,
     NumberToCodes,
     OpDeclaration,
+    Open,
+    NextStream,
+    PartialStringTail,
+    PeekByte,
+    PeekChar,
+    PeekCode,
+    PointsToContinuationResetMarker,
+    PutByte,
+    PutChar,
+    PutChars,
+    PutCode,
     REPL(REPLCodePtr),
     ReadQueryTerm,
     ReadTerm,
-    RedoAttrVarBindings,
+    RedoAttrVarBinding,
     RemoveCallPolicyCheck,
     RemoveInferenceCounter,
+    ResetContinuationMarker,
     ResetGlobalVarAtKey,
     ResetGlobalVarAtOffset,
     RetractClause,
     RestoreCutPolicy,
     SetCutPoint(RegType),
+    SetInput,
+    SetOutput,
     StoreGlobalVar,
     StoreGlobalVarWithOffset,
+    StreamProperty,
+    SetStreamPosition,
     InferenceLevel,
     CleanUpBlock,
     EraseBall,
@@ -223,21 +269,53 @@ pub enum SystemClauseType {
     GetCutPoint,
     GetDoubleQuotes,
     InstallNewBlock,
+    Maybe,
+    CpuNow,
+    CurrentTime,
+    QuotedToken,
+    ReadTermFromChars,
     ResetBlock,
-    ReturnFromAttributeGoals,
     ReturnFromVerifyAttr,
     SetBall,
     SetCutPointByDefault(RegType),
     SetDoubleQuotes,
+    SetSeed,
     SkipMaxList,
+    Sleep,
+    SocketClientOpen,
+    SocketServerOpen,
+    SocketServerAccept,
+    SocketServerClose,
     Succeed,
+    TermAttributedVariables,
     TermVariables,
     TruncateLiftedHeapTo,
     UnifyWithOccursCheck,
+    UnwindEnvironments,
     UnwindStack,
     Variant,
     WAMInstructions,
     WriteTerm,
+    WriteTermToChars,
+    ScryerPrologVersion,
+    CryptoRandomByte,
+    CryptoDataHash,
+    CryptoDataHKDF,
+    CryptoPasswordHash,
+    CryptoDataEncrypt,
+    CryptoDataDecrypt,
+    CryptoCurveScalarMult,
+    Ed25519Sign,
+    Ed25519Verify,
+    Ed25519NewKeyPair,
+    Ed25519KeyPairPublicKey,
+    Curve25519ScalarMult,
+    LoadHTML,
+    LoadXML,
+    GetEnv,
+    SetEnv,
+    UnsetEnv,
+    CharsBase64,
 }
 
 impl SystemClauseType {
@@ -247,37 +325,50 @@ impl SystemClauseType {
             &SystemClauseType::AbolishModuleClause => clause_name!("$abolish_module_clause"),
             &SystemClauseType::AssertDynamicPredicateToBack => clause_name!("$assertz"),
             &SystemClauseType::AssertDynamicPredicateToFront => clause_name!("$asserta"),
+            &SystemClauseType::AtEndOfExpansion => clause_name!("$at_end_of_expansion"),
             &SystemClauseType::AtomChars => clause_name!("$atom_chars"),
             &SystemClauseType::AtomCodes => clause_name!("$atom_codes"),
             &SystemClauseType::AtomLength => clause_name!("$atom_length"),
-            &SystemClauseType::ModuleAssertDynamicPredicateToFront => {
-                clause_name!("$module_asserta")
-            }
-            &SystemClauseType::ModuleAssertDynamicPredicateToBack => {
-                clause_name!("$module_assertz")
-            }
+            &SystemClauseType::BindFromRegister => clause_name!("$bind_from_register"),
+            &SystemClauseType::CallContinuation => clause_name!("$call_continuation"),
             &SystemClauseType::CharCode => clause_name!("$char_code"),
+            &SystemClauseType::CharType => clause_name!("$char_type"),
             &SystemClauseType::CharsToNumber => clause_name!("$chars_to_number"),
-            &SystemClauseType::CodesToNumber => clause_name!("$codes_to_number"),
             &SystemClauseType::CheckCutPoint => clause_name!("$check_cp"),
+            &SystemClauseType::ClearAttributeGoals => clause_name!("$clear_attribute_goals"),
+            &SystemClauseType::CloneAttributeGoals => clause_name!("$clone_attribute_goals"),
+            &SystemClauseType::CodesToNumber => clause_name!("$codes_to_number"),
+            &SystemClauseType::CopyTermWithoutAttrVars => clause_name!("$copy_term_without_attr_vars"),
+            &SystemClauseType::CreatePartialString => clause_name!("$create_partial_string"),
+            &SystemClauseType::CurrentInput => clause_name!("$current_input"),
+            &SystemClauseType::CurrentHostname => clause_name!("$current_hostname"),
+            &SystemClauseType::CurrentOutput => clause_name!("$current_output"),
+            &SystemClauseType::DirectoryFiles => clause_name!("$directory_files"),
+            &SystemClauseType::FileSize => clause_name!("$file_size"),
+            &SystemClauseType::FileExists => clause_name!("$file_exists"),
+            &SystemClauseType::DirectoryExists => clause_name!("$directory_exists"),
+            &SystemClauseType::DirectorySeparator => clause_name!("$directory_separator"),
+            &SystemClauseType::MakeDirectory => clause_name!("$make_directory"),
+            &SystemClauseType::DeleteFile => clause_name!("$delete_file"),
+            &SystemClauseType::WorkingDirectory => clause_name!("$working_directory"),
+            &SystemClauseType::PathCanonical => clause_name!("$path_canonical"),
+            &SystemClauseType::FileTime => clause_name!("$file_time"),
             &SystemClauseType::REPL(REPLCodePtr::CompileBatch) => clause_name!("$compile_batch"),
-            &SystemClauseType::REPL(REPLCodePtr::SubmitQueryAndPrintResults) => {
-                clause_name!("$submit_query_and_print_results")
+            &SystemClauseType::REPL(REPLCodePtr::UseModule) => clause_name!("$use_module"),
+            &SystemClauseType::REPL(REPLCodePtr::UseQualifiedModule) => {
+                    clause_name!("$use_qualified_module")
             }
-	    &SystemClauseType::REPL(REPLCodePtr::UseModule) => clause_name!("$use_module"),
-	    &SystemClauseType::REPL(REPLCodePtr::UseQualifiedModule) => {
-		clause_name!("$use_qualified_module")
-	    }
-	    &SystemClauseType::REPL(REPLCodePtr::UseModuleFromFile) => {
-		clause_name!("$use_module_from_file")
-	    }
-	    &SystemClauseType::REPL(REPLCodePtr::UseQualifiedModuleFromFile) => {
-		clause_name!("$use_qualified_module_from_file")
-	    }
+            &SystemClauseType::REPL(REPLCodePtr::UseModuleFromFile) => {
+                    clause_name!("$use_module_from_file")
+            }
+            &SystemClauseType::REPL(REPLCodePtr::UseQualifiedModuleFromFile) => {
+                    clause_name!("$use_qualified_module_from_file")
+            }
+            &SystemClauseType::Close => clause_name!("$close"),
             &SystemClauseType::CopyToLiftedHeap => clause_name!("$copy_to_lh"),
             &SystemClauseType::DeleteAttribute => clause_name!("$del_attr_non_head"),
             &SystemClauseType::DeleteHeadAttribute => clause_name!("$del_attr_head"),
-            &SystemClauseType::DynamicModuleResolution => clause_name!("$module_call"),
+            &SystemClauseType::DynamicModuleResolution(_) => clause_name!("$module_call"),
             &SystemClauseType::EnqueueAttributeGoal => clause_name!("$enqueue_attribute_goal"),
             &SystemClauseType::EnqueueAttributedVar => clause_name!("$enqueue_attr_var"),
             &SystemClauseType::ExpandTerm => clause_name!("$expand_term"),
@@ -286,7 +377,14 @@ impl SystemClauseType {
             &SystemClauseType::FetchGlobalVarWithOffset => {
                 clause_name!("$fetch_global_var_with_offset")
             }
+            &SystemClauseType::FirstStream => clause_name!("$first_stream"),
+            &SystemClauseType::FlushOutput => clause_name!("$flush_output"),
+            &SystemClauseType::GetByte => clause_name!("$get_byte"),
             &SystemClauseType::GetChar => clause_name!("$get_char"),
+            &SystemClauseType::GetNChars => clause_name!("$get_n_chars"),
+            &SystemClauseType::GetCode => clause_name!("$get_code"),
+            &SystemClauseType::GetSingleChar => clause_name!("$get_single_char"),
+            &SystemClauseType::ResetAttrVarState => clause_name!("$reset_attr_var_state"),
             &SystemClauseType::TruncateIfNoLiftedHeapGrowth => {
                 clause_name!("$truncate_if_no_lh_growth")
             }
@@ -298,6 +396,7 @@ impl SystemClauseType {
                 clause_name!("$get_attr_var_queue_delim")
             }
             &SystemClauseType::GetAttrVarQueueBeyond => clause_name!("$get_attr_var_queue_beyond"),
+            &SystemClauseType::GetContinuationChunk => clause_name!("$get_cont_chunk"),
             &SystemClauseType::GetLiftedHeapFromOffset => clause_name!("$get_lh_from_offset"),
             &SystemClauseType::GetLiftedHeapFromOffsetDiff => {
                 clause_name!("$get_lh_from_offset_diff")
@@ -313,22 +412,62 @@ impl SystemClauseType {
             &SystemClauseType::GetSCCCleaner => clause_name!("$get_scc_cleaner"),
             &SystemClauseType::Halt => clause_name!("$halt"),
             &SystemClauseType::HeadIsDynamic => clause_name!("$head_is_dynamic"),
-            &SystemClauseType::OpDeclaration => clause_name!("$op$"),
+            &SystemClauseType::Open => clause_name!("$open"),
+            &SystemClauseType::OpDeclaration => clause_name!("$op"),
             &SystemClauseType::InstallSCCCleaner => clause_name!("$install_scc_cleaner"),
             &SystemClauseType::InstallInferenceCounter => {
                 clause_name!("$install_inference_counter")
             }
+            &SystemClauseType::IsPartialString => clause_name!("$is_partial_string"),
+            &SystemClauseType::PartialStringTail => clause_name!("$partial_string_tail"),
+            &SystemClauseType::PeekByte => clause_name!("$peek_byte"),
+            &SystemClauseType::PeekChar => clause_name!("$peek_char"),
+            &SystemClauseType::PeekCode => clause_name!("$peek_code"),
             &SystemClauseType::LiftedHeapLength => clause_name!("$lh_length"),
+            &SystemClauseType::Maybe => clause_name!("maybe"),
+            &SystemClauseType::CpuNow => clause_name!("$cpu_now"),
+            &SystemClauseType::CurrentTime => clause_name!("$current_time"),
+            &SystemClauseType::ModuleAssertDynamicPredicateToFront => {
+                clause_name!("$module_asserta")
+            }
+            &SystemClauseType::ModuleAssertDynamicPredicateToBack => {
+                clause_name!("$module_assertz")
+            }
             &SystemClauseType::ModuleHeadIsDynamic => clause_name!("$module_head_is_dynamic"),
+            &SystemClauseType::ModuleExists => clause_name!("$module_exists"),
             &SystemClauseType::ModuleOf => clause_name!("$module_of"),
+            &SystemClauseType::NextStream => clause_name!("$next_stream"),
             &SystemClauseType::NoSuchPredicate => clause_name!("$no_such_predicate"),
             &SystemClauseType::NumberToChars => clause_name!("$number_to_chars"),
             &SystemClauseType::NumberToCodes => clause_name!("$number_to_codes"),
-            &SystemClauseType::RedoAttrVarBindings => clause_name!("$redo_attr_var_bindings"),
+            &SystemClauseType::PointsToContinuationResetMarker => {
+                clause_name!("$points_to_cont_reset_marker")
+            }
+            &SystemClauseType::PutByte => {
+                clause_name!("$put_byte")
+            }
+            &SystemClauseType::PutChar => {
+                clause_name!("$put_char")
+            }
+            &SystemClauseType::PutChars => {
+                clause_name!("$put_chars")
+            }
+            &SystemClauseType::PutCode => {
+                clause_name!("$put_code")
+            }
+            &SystemClauseType::QuotedToken => {
+                clause_name!("$quoted_token")
+            }
+            &SystemClauseType::RedoAttrVarBinding => clause_name!("$redo_attr_var_binding"),
             &SystemClauseType::RemoveCallPolicyCheck => clause_name!("$remove_call_policy_check"),
             &SystemClauseType::RemoveInferenceCounter => clause_name!("$remove_inference_counter"),
             &SystemClauseType::RestoreCutPolicy => clause_name!("$restore_cut_policy"),
             &SystemClauseType::SetCutPoint(_) => clause_name!("$set_cp"),
+            &SystemClauseType::SetInput => clause_name!("$set_input"),
+            &SystemClauseType::SetOutput => clause_name!("$set_output"),
+            &SystemClauseType::SetSeed => clause_name!("$set_seed"),
+            &SystemClauseType::StreamProperty => clause_name!("$stream_property"),
+            &SystemClauseType::SetStreamPosition => clause_name!("$set_stream_position"),
             &SystemClauseType::StoreGlobalVar => clause_name!("$store_global_var"),
             &SystemClauseType::StoreGlobalVarWithOffset => {
                 clause_name!("$store_global_var_with_offset")
@@ -342,62 +481,129 @@ impl SystemClauseType {
             &SystemClauseType::GetCurrentBlock => clause_name!("$get_current_block"),
             &SystemClauseType::InstallNewBlock => clause_name!("$install_new_block"),
             &SystemClauseType::ModuleRetractClause => clause_name!("$module_retract_clause"),
+            &SystemClauseType::NextEP => clause_name!("$nextEP"),
             &SystemClauseType::ReadQueryTerm => clause_name!("$read_query_term"),
             &SystemClauseType::ReadTerm => clause_name!("$read_term"),
+            &SystemClauseType::ReadTermFromChars => clause_name!("$read_term_from_chars"),
             &SystemClauseType::ResetGlobalVarAtKey => clause_name!("$reset_global_var_at_key"),
             &SystemClauseType::ResetGlobalVarAtOffset => clause_name!("$reset_global_var_at_offset"),
             &SystemClauseType::RetractClause => clause_name!("$retract_clause"),
             &SystemClauseType::ResetBlock => clause_name!("$reset_block"),
-            &SystemClauseType::ReturnFromAttributeGoals => {
-                clause_name!("$return_from_attribute_goals")
-            }
+            &SystemClauseType::ResetContinuationMarker => clause_name!("$reset_cont_marker"),
             &SystemClauseType::ReturnFromVerifyAttr => clause_name!("$return_from_verify_attr"),
             &SystemClauseType::SetBall => clause_name!("$set_ball"),
             &SystemClauseType::SetCutPointByDefault(_) => clause_name!("$set_cp_by_default"),
             &SystemClauseType::SetDoubleQuotes => clause_name!("$set_double_quotes"),
             &SystemClauseType::SkipMaxList => clause_name!("$skip_max_list"),
+            &SystemClauseType::Sleep => clause_name!("$sleep"),
+            &SystemClauseType::SocketClientOpen => clause_name!("$socket_client_open"),
+            &SystemClauseType::SocketServerOpen => clause_name!("$socket_server_open"),
+            &SystemClauseType::SocketServerAccept => clause_name!("$socket_server_accept"),
+            &SystemClauseType::SocketServerClose => clause_name!("$socket_server_close"),
             &SystemClauseType::Succeed => clause_name!("$succeed"),
+            &SystemClauseType::TermAttributedVariables => clause_name!("$term_attributed_variables"),
             &SystemClauseType::TermVariables => clause_name!("$term_variables"),
             &SystemClauseType::TruncateLiftedHeapTo => clause_name!("$truncate_lh_to"),
             &SystemClauseType::UnifyWithOccursCheck => clause_name!("$unify_with_occurs_check"),
+            &SystemClauseType::UnwindEnvironments => clause_name!("$unwind_environments"),
             &SystemClauseType::UnwindStack => clause_name!("$unwind_stack"),
             &SystemClauseType::Variant => clause_name!("$variant"),
             &SystemClauseType::WAMInstructions => clause_name!("$wam_instructions"),
             &SystemClauseType::WriteTerm => clause_name!("$write_term"),
+            &SystemClauseType::WriteTermToChars => clause_name!("$write_term_to_chars"),
+            &SystemClauseType::ScryerPrologVersion => clause_name!("$scryer_prolog_version"),
+            &SystemClauseType::CryptoRandomByte => clause_name!("$crypto_random_byte"),
+            &SystemClauseType::CryptoDataHash => clause_name!("$crypto_data_hash"),
+            &SystemClauseType::CryptoDataHKDF => clause_name!("$crypto_data_hkdf"),
+            &SystemClauseType::CryptoPasswordHash => clause_name!("$crypto_password_hash"),
+            &SystemClauseType::CryptoDataEncrypt => clause_name!("$crypto_data_encrypt"),
+            &SystemClauseType::CryptoDataDecrypt => clause_name!("$crypto_data_decrypt"),
+            &SystemClauseType::CryptoCurveScalarMult => clause_name!("$crypto_curve_scalar_mult"),
+            &SystemClauseType::Ed25519Sign => clause_name!("$ed25519_sign"),
+            &SystemClauseType::Ed25519Verify => clause_name!("$ed25519_verify"),
+            &SystemClauseType::Ed25519NewKeyPair => clause_name!("$ed25519_new_keypair"),
+            &SystemClauseType::Ed25519KeyPairPublicKey => clause_name!("$ed25519_keypair_public_key"),
+            &SystemClauseType::Curve25519ScalarMult => clause_name!("$curve25519_scalar_mult"),
+            &SystemClauseType::LoadHTML => clause_name!("$load_html"),
+            &SystemClauseType::LoadXML => clause_name!("$load_xml"),
+            &SystemClauseType::GetEnv => clause_name!("$getenv"),
+            &SystemClauseType::SetEnv => clause_name!("$setenv"),
+            &SystemClauseType::UnsetEnv => clause_name!("$unsetenv"),
+            &SystemClauseType::CharsBase64 => clause_name!("$chars_base64"),
         }
     }
 
     pub fn from(name: &str, arity: usize) -> Option<SystemClauseType> {
         match (name, arity) {
             ("$abolish_clause", 2) => Some(SystemClauseType::AbolishClause),
+            ("$at_end_of_expansion", 0) => Some(SystemClauseType::AtEndOfExpansion),
             ("$atom_chars", 2) => Some(SystemClauseType::AtomChars),
             ("$atom_codes", 2) => Some(SystemClauseType::AtomCodes),
             ("$atom_length", 2) => Some(SystemClauseType::AtomLength),
             ("$abolish_module_clause", 3) => Some(SystemClauseType::AbolishModuleClause),
+            ("$bind_from_register", 2) => Some(SystemClauseType::BindFromRegister),
             ("$module_asserta", 5) => Some(SystemClauseType::ModuleAssertDynamicPredicateToFront),
             ("$module_assertz", 5) => Some(SystemClauseType::ModuleAssertDynamicPredicateToBack),
             ("$asserta", 4) => Some(SystemClauseType::AssertDynamicPredicateToFront),
             ("$assertz", 4) => Some(SystemClauseType::AssertDynamicPredicateToBack),
+            ("$call_continuation", 1) => Some(SystemClauseType::CallContinuation),
             ("$char_code", 2) => Some(SystemClauseType::CharCode),
+            ("$char_type", 2) => Some(SystemClauseType::CharType),
             ("$chars_to_number", 2) => Some(SystemClauseType::CharsToNumber),
+            ("$clear_attribute_goals", 0) => Some(SystemClauseType::ClearAttributeGoals),
+            ("$clone_attribute_goals", 1) => Some(SystemClauseType::CloneAttributeGoals),
             ("$codes_to_number", 2) => Some(SystemClauseType::CodesToNumber),
+            ("$copy_term_without_attr_vars", 2) => Some(SystemClauseType::CopyTermWithoutAttrVars),
+            ("$create_partial_string", 3) => Some(SystemClauseType::CreatePartialString),
             ("$check_cp", 1) => Some(SystemClauseType::CheckCutPoint),
             ("$compile_batch", 0) => Some(SystemClauseType::REPL(REPLCodePtr::CompileBatch)),
             ("$copy_to_lh", 2) => Some(SystemClauseType::CopyToLiftedHeap),
+            ("$close", 2) => Some(SystemClauseType::Close),
+            ("$current_hostname", 1) => Some(SystemClauseType::CurrentHostname),
+            ("$current_input", 1) => Some(SystemClauseType::CurrentInput),
+            ("$current_output", 1) => Some(SystemClauseType::CurrentOutput),
+            ("$first_stream", 1) => Some(SystemClauseType::FirstStream),
+            ("$next_stream", 2) => Some(SystemClauseType::NextStream),
+            ("$flush_output", 1) => Some(SystemClauseType::FlushOutput),
             ("$del_attr_non_head", 1) => Some(SystemClauseType::DeleteAttribute),
             ("$del_attr_head", 1) => Some(SystemClauseType::DeleteHeadAttribute),
             ("$get_next_db_ref", 2) => Some(SystemClauseType::GetNextDBRef),
             ("$get_next_op_db_ref", 2) => Some(SystemClauseType::GetNextOpDBRef),
             ("$lookup_db_ref", 3) => Some(SystemClauseType::LookupDBRef),
             ("$lookup_op_db_ref", 4) => Some(SystemClauseType::LookupOpDBRef),
-            ("$module_call", 2) => Some(SystemClauseType::DynamicModuleResolution),
+            ("$module_call", _) => Some(SystemClauseType::DynamicModuleResolution(arity - 2)),
             ("$enqueue_attribute_goal", 1) => Some(SystemClauseType::EnqueueAttributeGoal),
             ("$enqueue_attr_var", 1) => Some(SystemClauseType::EnqueueAttributedVar),
+            ("$partial_string_tail", 2) => Some(SystemClauseType::PartialStringTail),
+            ("$peek_byte", 2) => Some(SystemClauseType::PeekByte),
+            ("$peek_char", 2) => Some(SystemClauseType::PeekChar),
+            ("$peek_code", 2) => Some(SystemClauseType::PeekCode),
+            ("$is_partial_string", 1) => Some(SystemClauseType::IsPartialString),
             ("$expand_term", 2) => Some(SystemClauseType::ExpandTerm),
             ("$expand_goal", 2) => Some(SystemClauseType::ExpandGoal),
             ("$fetch_global_var", 2) => Some(SystemClauseType::FetchGlobalVar),
             ("$fetch_global_var_with_offset", 3) => Some(SystemClauseType::FetchGlobalVarWithOffset),
-            ("$get_char", 1) => Some(SystemClauseType::GetChar),
+            ("$get_byte", 2) => Some(SystemClauseType::GetByte),
+            ("$get_char", 2) => Some(SystemClauseType::GetChar),
+            ("$get_n_chars", 3) => Some(SystemClauseType::GetNChars),
+            ("$get_code", 2) => Some(SystemClauseType::GetCode),
+            ("$get_single_char", 1) => Some(SystemClauseType::GetSingleChar),
+            ("$points_to_cont_reset_marker", 1) => {
+                Some(SystemClauseType::PointsToContinuationResetMarker)
+            }
+            ("$put_byte", 2) => {
+                Some(SystemClauseType::PutByte)
+            }
+            ("$put_char", 2) => {
+                Some(SystemClauseType::PutChar)
+            }
+            ("$put_chars", 2) => {
+                Some(SystemClauseType::PutChars)
+            }
+            ("$put_code", 2) => {
+                Some(SystemClauseType::PutCode)
+            }
+            ("$reset_attr_var_state", 0) => Some(SystemClauseType::ResetAttrVarState),
             ("$truncate_if_no_lh_growth", 1) => {
                 Some(SystemClauseType::TruncateIfNoLiftedHeapGrowth)
             }
@@ -412,11 +618,15 @@ impl SystemClauseType {
             ("$get_lh_from_offset_diff", 3) => Some(SystemClauseType::GetLiftedHeapFromOffsetDiff),
             ("$get_double_quotes", 1) => Some(SystemClauseType::GetDoubleQuotes),
             ("$get_scc_cleaner", 1) => Some(SystemClauseType::GetSCCCleaner),
-            ("$halt", 0) => Some(SystemClauseType::Halt),
+            ("$halt", 1) => Some(SystemClauseType::Halt),
             ("$head_is_dynamic", 1) => Some(SystemClauseType::HeadIsDynamic),
             ("$install_scc_cleaner", 2) => Some(SystemClauseType::InstallSCCCleaner),
             ("$install_inference_counter", 3) => Some(SystemClauseType::InstallInferenceCounter),
             ("$lh_length", 1) => Some(SystemClauseType::LiftedHeapLength),
+            ("$maybe", 0) => Some(SystemClauseType::Maybe),
+            ("$cpu_now", 1) => Some(SystemClauseType::CpuNow),
+            ("$current_time", 1) => Some(SystemClauseType::CurrentTime),
+            ("$module_exists", 1) => Some(SystemClauseType::ModuleExists),
             ("$module_of", 2) => Some(SystemClauseType::ModuleOf),
             ("$module_retract_clause", 5) => Some(SystemClauseType::ModuleRetractClause),
             ("$module_head_is_dynamic", 2) => Some(SystemClauseType::ModuleHeadIsDynamic),
@@ -424,11 +634,16 @@ impl SystemClauseType {
             ("$number_to_chars", 2) => Some(SystemClauseType::NumberToChars),
             ("$number_to_codes", 2) => Some(SystemClauseType::NumberToCodes),
             ("$op", 3) => Some(SystemClauseType::OpDeclaration),
-            ("$redo_attr_var_bindings", 0) => Some(SystemClauseType::RedoAttrVarBindings),
+            ("$open", 7) => Some(SystemClauseType::Open),
+            ("$redo_attr_var_binding", 2) => Some(SystemClauseType::RedoAttrVarBinding),
             ("$remove_call_policy_check", 1) => Some(SystemClauseType::RemoveCallPolicyCheck),
             ("$remove_inference_counter", 2) => Some(SystemClauseType::RemoveInferenceCounter),
             ("$restore_cut_policy", 0) => Some(SystemClauseType::RestoreCutPolicy),
             ("$set_cp", 1) => Some(SystemClauseType::SetCutPoint(temp_v!(1))),
+            ("$set_input", 1) => Some(SystemClauseType::SetInput),
+            ("$set_output", 1) => Some(SystemClauseType::SetOutput),
+            ("$stream_property", 3) => Some(SystemClauseType::StreamProperty),
+            ("$set_stream_position", 2) => Some(SystemClauseType::SetStreamPosition),
             ("$inference_level", 2) => Some(SystemClauseType::InferenceLevel),
             ("$clean_up_block", 1) => Some(SystemClauseType::CleanUpBlock),
             ("$erase_ball", 0) => Some(SystemClauseType::EraseBall),
@@ -436,52 +651,90 @@ impl SystemClauseType {
             ("$get_attr_var_queue_beyond", 2) => Some(SystemClauseType::GetAttrVarQueueBeyond),
             ("$get_attr_var_queue_delim", 1) => Some(SystemClauseType::GetAttrVarQueueDelimiter),
             ("$get_ball", 1) => Some(SystemClauseType::GetBall),
+            ("$get_cont_chunk", 3) => Some(SystemClauseType::GetContinuationChunk),
             ("$get_current_block", 1) => Some(SystemClauseType::GetCurrentBlock),
             ("$get_cp", 1) => Some(SystemClauseType::GetCutPoint),
             ("$install_new_block", 1) => Some(SystemClauseType::InstallNewBlock),
-            ("$read_query_term", 2) => Some(SystemClauseType::ReadQueryTerm),
-            ("$read_term", 2) => Some(SystemClauseType::ReadTerm),
+            ("$quoted_token", 1) => Some(SystemClauseType::QuotedToken),
+            ("$nextEP", 3) => Some(SystemClauseType::NextEP),
+            ("$read_query_term", 5) => Some(SystemClauseType::ReadQueryTerm),
+            ("$read_term", 5) => Some(SystemClauseType::ReadTerm),
+            ("$read_term_from_chars", 2) => Some(SystemClauseType::ReadTermFromChars),
             ("$reset_block", 1) => Some(SystemClauseType::ResetBlock),
+            ("$reset_cont_marker", 0) => Some(SystemClauseType::ResetContinuationMarker),
             ("$reset_global_var_at_key", 1) => Some(SystemClauseType::ResetGlobalVarAtKey),
             ("$reset_global_var_at_offset", 3) => Some(SystemClauseType::ResetGlobalVarAtOffset),
             ("$retract_clause", 4) => Some(SystemClauseType::RetractClause),
-            ("$return_from_attribute_goals", 0) => Some(SystemClauseType::ReturnFromAttributeGoals),
             ("$return_from_verify_attr", 0) => Some(SystemClauseType::ReturnFromVerifyAttr),
             ("$set_ball", 1) => Some(SystemClauseType::SetBall),
             ("$set_cp_by_default", 1) => Some(SystemClauseType::SetCutPointByDefault(temp_v!(1))),
             ("$set_double_quotes", 1) => Some(SystemClauseType::SetDoubleQuotes),
+            ("$set_seed", 1) => Some(SystemClauseType::SetSeed),
             ("$skip_max_list", 4) => Some(SystemClauseType::SkipMaxList),
+            ("$sleep", 1) => Some(SystemClauseType::Sleep),
+            ("$socket_client_open", 8) => Some(SystemClauseType::SocketClientOpen),
+            ("$socket_server_open", 3) => Some(SystemClauseType::SocketServerOpen),
+            ("$socket_server_accept", 7) => Some(SystemClauseType::SocketServerAccept),
+            ("$socket_server_close", 1) => Some(SystemClauseType::SocketServerClose),
             ("$store_global_var", 2) => Some(SystemClauseType::StoreGlobalVar),
             ("$store_global_var_with_offset", 2) => Some(SystemClauseType::StoreGlobalVarWithOffset),
-            ("$submit_query_and_print_results", 2) => Some(SystemClauseType::REPL(
-                REPLCodePtr::SubmitQueryAndPrintResults,
-            )),
+            ("$term_attributed_variables", 2) => Some(SystemClauseType::TermAttributedVariables),
             ("$term_variables", 2) => Some(SystemClauseType::TermVariables),
             ("$truncate_lh_to", 1) => Some(SystemClauseType::TruncateLiftedHeapTo),
+            ("$unwind_environments", 0) => Some(SystemClauseType::UnwindEnvironments),
             ("$unwind_stack", 0) => Some(SystemClauseType::UnwindStack),
             ("$unify_with_occurs_check", 2) => Some(SystemClauseType::UnifyWithOccursCheck),
-	    ("$use_module", 1) => Some(SystemClauseType::REPL(REPLCodePtr::UseModule)),
-	    ("$use_module_from_file", 1) =>
-		Some(SystemClauseType::REPL(REPLCodePtr::UseModuleFromFile)),	    
-	    ("$use_qualified_module", 2) =>
-		Some(SystemClauseType::REPL(REPLCodePtr::UseQualifiedModule)),
-	    ("$use_qualified_module_from_file", 2) =>
-		Some(SystemClauseType::REPL(REPLCodePtr::UseQualifiedModuleFromFile)),
+            ("$directory_files", 2) => Some(SystemClauseType::DirectoryFiles),
+            ("$file_size", 2) => Some(SystemClauseType::FileSize),
+            ("$file_exists", 1) => Some(SystemClauseType::FileExists),
+            ("$directory_exists", 1) => Some(SystemClauseType::DirectoryExists),
+            ("$directory_separator", 1) => Some(SystemClauseType::DirectorySeparator),
+            ("$make_directory", 1) => Some(SystemClauseType::MakeDirectory),
+            ("$delete_file", 1) => Some(SystemClauseType::DeleteFile),
+            ("$working_directory", 2) => Some(SystemClauseType::WorkingDirectory),
+            ("$path_canonical", 2) => Some(SystemClauseType::PathCanonical),
+            ("$file_time", 3) => Some(SystemClauseType::FileTime),
+            ("$use_module", 1) => Some(SystemClauseType::REPL(REPLCodePtr::UseModule)),
+            ("$use_module_from_file", 1) =>
+                    Some(SystemClauseType::REPL(REPLCodePtr::UseModuleFromFile)),
+            ("$use_qualified_module", 2) =>
+                    Some(SystemClauseType::REPL(REPLCodePtr::UseQualifiedModule)),
+            ("$use_qualified_module_from_file", 2) =>
+                    Some(SystemClauseType::REPL(REPLCodePtr::UseQualifiedModuleFromFile)),
             ("$variant", 2) => Some(SystemClauseType::Variant),
-            ("$write_term", 5) => Some(SystemClauseType::WriteTerm),
             ("$wam_instructions", 3) => Some(SystemClauseType::WAMInstructions),
+            ("$write_term", 7) => Some(SystemClauseType::WriteTerm),
+            ("$write_term_to_chars", 7) => Some(SystemClauseType::WriteTermToChars),
+            ("$scryer_prolog_version", 1) => Some(SystemClauseType::ScryerPrologVersion),
+            ("$crypto_random_byte", 1) => Some(SystemClauseType::CryptoRandomByte),
+            ("$crypto_data_hash", 4) => Some(SystemClauseType::CryptoDataHash),
+            ("$crypto_data_hkdf", 7) => Some(SystemClauseType::CryptoDataHKDF),
+            ("$crypto_password_hash", 4) => Some(SystemClauseType::CryptoPasswordHash),
+            ("$crypto_data_encrypt", 6) => Some(SystemClauseType::CryptoDataEncrypt),
+            ("$crypto_data_decrypt", 6) => Some(SystemClauseType::CryptoDataDecrypt),
+            ("$crypto_curve_scalar_mult", 5) => Some(SystemClauseType::CryptoCurveScalarMult),
+            ("$ed25519_sign", 5) => Some(SystemClauseType::Ed25519Sign),
+            ("$ed25519_verify", 5) => Some(SystemClauseType::Ed25519Verify),
+            ("$ed25519_new_keypair", 1) => Some(SystemClauseType::Ed25519NewKeyPair),
+            ("$ed25519_keypair_public_key", 3) => Some(SystemClauseType::Ed25519KeyPairPublicKey),
+            ("$curve25519_scalar_mult", 3) => Some(SystemClauseType::Curve25519ScalarMult),
+            ("$load_html", 3) => Some(SystemClauseType::LoadHTML),
+            ("$load_xml", 3) => Some(SystemClauseType::LoadXML),
+            ("$getenv", 2) => Some(SystemClauseType::GetEnv),
+            ("$setenv", 2) => Some(SystemClauseType::SetEnv),
+            ("$unsetenv", 1) => Some(SystemClauseType::UnsetEnv),
+            ("$chars_base64", 4) => Some(SystemClauseType::CharsBase64),
             _ => None,
         }
     }
 }
 
-#[derive(Clone, Eq, PartialEq)]
+#[derive(Debug, Clone, Eq, PartialEq)]
 pub enum BuiltInClauseType {
     AcyclicTerm,
     Arg,
     Compare,
     CompareTerm(CompareTermQT),
-    CyclicTerm,
     CopyTerm,
     Eq,
     Functor,
@@ -490,12 +743,11 @@ pub enum BuiltInClauseType {
     KeySort,
     Nl,
     NotEq,
-    PartialString,
     Read,
     Sort,
 }
 
-#[derive(Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq)]
 pub enum ClauseType {
     BuiltIn(BuiltInClauseType),
     CallN,
@@ -513,7 +765,6 @@ impl BuiltInClauseType {
             &BuiltInClauseType::Arg => clause_name!("arg"),
             &BuiltInClauseType::Compare => clause_name!("compare"),
             &BuiltInClauseType::CompareTerm(qt) => clause_name!(qt.name()),
-            &BuiltInClauseType::CyclicTerm => clause_name!("cyclic_term"),
             &BuiltInClauseType::CopyTerm => clause_name!("copy_term"),
             &BuiltInClauseType::Eq => clause_name!("=="),
             &BuiltInClauseType::Functor => clause_name!("functor"),
@@ -522,7 +773,6 @@ impl BuiltInClauseType {
             &BuiltInClauseType::KeySort => clause_name!("keysort"),
             &BuiltInClauseType::Nl => clause_name!("nl"),
             &BuiltInClauseType::NotEq => clause_name!("\\=="),
-            &BuiltInClauseType::PartialString => clause_name!("partial_string"),
             &BuiltInClauseType::Read => clause_name!("read"),
             &BuiltInClauseType::Sort => clause_name!("sort"),
         }
@@ -534,7 +784,6 @@ impl BuiltInClauseType {
             &BuiltInClauseType::Arg => 3,
             &BuiltInClauseType::Compare => 2,
             &BuiltInClauseType::CompareTerm(_) => 2,
-            &BuiltInClauseType::CyclicTerm => 1,
             &BuiltInClauseType::CopyTerm => 2,
             &BuiltInClauseType::Eq => 2,
             &BuiltInClauseType::Functor => 3,
@@ -543,7 +792,6 @@ impl BuiltInClauseType {
             &BuiltInClauseType::KeySort => 2,
             &BuiltInClauseType::NotEq => 2,
             &BuiltInClauseType::Nl => 0,
-            &BuiltInClauseType::PartialString => 1,
             &BuiltInClauseType::Read => 1,
             &BuiltInClauseType::Sort => 2,
         }
@@ -565,8 +813,8 @@ impl ClauseType {
 
     pub fn name(&self) -> ClauseName {
         match self {
-            &ClauseType::CallN => clause_name!("call"),
             &ClauseType::BuiltIn(ref built_in) => built_in.name(),
+            &ClauseType::CallN => clause_name!("call"),
             &ClauseType::Hook(ref hook) => hook.name(),
             &ClauseType::Inlined(ref inlined) => clause_name!(inlined.name()),
             &ClauseType::Op(ref name, ..) => name.clone(),

src/codegen.rs

@@ -1,29 +1,30 @@
-use prolog_parser::ast::*;
+use crate::prolog_parser::ast::*;
 
-use crate::prolog::allocator::*;
-use crate::prolog::arithmetic::*;
-use crate::prolog::clause_types::*;
-use crate::prolog::fixtures::*;
-use crate::prolog::forms::*;
-use crate::prolog::indexing::*;
-use crate::prolog::instructions::*;
-use crate::prolog::iterators::*;
-use crate::prolog::machine::machine_indices::*;
-use crate::prolog::targets::*;
+use crate::allocator::*;
+use crate::arithmetic::*;
+use crate::clause_types::*;
+use crate::fixtures::*;
+use crate::forms::*;
+use crate::indexing::*;
+use crate::instructions::*;
+use crate::iterators::*;
+use crate::machine::machine_indices::*;
+use crate::targets::*;
 
-use indexmap::IndexMap;
+use crate::indexmap::{IndexMap, IndexSet};
 
 use std::cell::Cell;
 use std::rc::Rc;
 use std::vec::Vec;
 
+#[derive(Debug)]
 pub struct CodeGenerator<TermMarker> {
-    flags: MachineFlags,
     marker: TermMarker,
     pub var_count: IndexMap<Rc<Var>, usize>,
     non_counted_bt: bool,
 }
 
+#[derive(Debug)]
 pub struct ConjunctInfo<'a> {
     pub perm_vs: VariableFixtures<'a>,
     pub num_of_chunks: usize,
@@ -51,68 +52,56 @@ impl<'a> ConjunctInfo<'a> {
         self.has_deep_cut as usize
     }
 
-    fn mark_unsafe_vars<Alloc: Allocator<'a>>(
+    fn mark_unsafe_vars(
         &self,
         mut unsafe_var_marker: UnsafeVarMarker,
-        marker: &Alloc,
-        code: &mut Code
+        code: &mut Code,
     ) {
-        // target the last goal of the rule for handling unsafe variables.
-        // we use this weird logic to find the last goal.
-        let right_index = if let Some(Line::Control(_)) = code.last() {
-            if code.len() >= 2 {
-                code.len() - 2
-            } else {
-                return;
-            }
-        } else {
-            if code.len() >= 1 {
-                code.len() - 1
-            } else {
-                return;
-            }
-        };
+        if code.is_empty() {
+            return;
+        }
 
-        let mut index = right_index;
+        let mut code_index = 0;
 
-        if let Line::Query(_) = &code[right_index] {
-            while let Line::Query(_) = &code[index] {
-                if index == 0 {
-                    break;
-                } else {
-                    index -= 1;
+        for phase in 0 .. {
+            while let Line::Query(ref query_instr) = &code[code_index] {
+                if !unsafe_var_marker.mark_safe_vars(query_instr) {
+                    unsafe_var_marker.mark_phase(query_instr, phase);
                 }
+
+                code_index += 1;
             }
 
-            if let Line::Query(_) = &code[index] {
+            if code_index + 1 < code.len() {
+                code_index += 1;
             } else {
-                index += 1;
+                break;
+            }
+        }
+
+        code_index = 0;
+
+        for phase in 0 .. {
+            while let Line::Query(ref mut query_instr) = &mut code[code_index] {
+                unsafe_var_marker.mark_unsafe_vars(query_instr, phase);
+                code_index += 1;
             }
 
-            unsafe_var_marker.record_unsafe_vars(&self.perm_vs, marker);
-
-            for line in code.iter() {
-                if let Line::Query(ref query_instr) = line {
-                    unsafe_var_marker.mark_safe_vars(query_instr);
-                }
-            }
-
-            for index in index..right_index + 1 {
-                if let &mut Line::Query(ref mut query_instr) = &mut code[index] {
-                    unsafe_var_marker.mark_unsafe_vars(query_instr);
-                }
+            if code_index + 1 < code.len() {
+                code_index += 1;
+            } else {
+                break;
             }
         }
     }
 }
 
 impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
-    pub fn new(non_counted_bt: bool, flags: MachineFlags) -> Self {
+    pub fn new(non_counted_bt: bool) -> Self {
         CodeGenerator {
             marker: Allocator::new(),
             var_count: IndexMap::new(),
             non_counted_bt,
-            flags,
         }
     }
 
@@ -133,31 +122,45 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
         *self.var_count.get(var).unwrap()
     }
 
+    fn mark_var_in_non_callable(
+        &mut self,
+        name: Rc<Var>,
+        term_loc: GenContext,
+        vr: &'a Cell<VarReg>,
+        code: &mut Code,
+    ) -> RegType {
+        let mut target = Vec::new();
+        self.marker.mark_var(name, Level::Shallow, vr, term_loc, &mut target);
+
+        if !target.is_empty() {
+            code.extend(target.into_iter().map(Line::Query));
+        }
+
+        vr.get().norm()
+    }
+
     fn mark_non_callable(
         &mut self,
         name: Rc<Var>,
-        arity: usize,
+        arg: usize,
         term_loc: GenContext,
         vr: &'a Cell<VarReg>,
         code: &mut Code,
     ) -> RegType {
         match self.marker.bindings().get(&name) {
-            Some(&VarData::Temp(_, t, _)) if t != 0 => RegType::Temp(t),
-            Some(&VarData::Perm(p)) if p != 0 => RegType::Perm(p),
-            _ => {
-                let mut target = Vec::new();
-
-                self.marker.reset_arg(arity);
-                self.marker
-                    .mark_var(name, Level::Shallow, vr, term_loc, &mut target);
-
-                if !target.is_empty() {
-                    for query_instr in target {
-                        code.push(Line::Query(query_instr));
-                    }
+            Some(&VarData::Temp(_, t, _)) if t != 0 => {
+                RegType::Temp(t)
+            }
+            Some(&VarData::Perm(p)) if p != 0 => {
+                if let GenContext::Last(_) = term_loc {
+                    self.mark_var_in_non_callable(name.clone(), term_loc, vr, code);
+                    temp_v!(arg)
+                } else {
+                    RegType::Perm(p)
                 }
-
-                vr.get().norm()
+            }
+            _ => {
+                self.mark_var_in_non_callable(name, term_loc, vr, code)
             }
         }
     }
@@ -176,40 +179,49 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
         target.push(Target::to_void(1));
     }
 
-    fn subterm_to_instr<Target>(
+    fn deep_var_instr<Target: CompilationTarget<'a>>(
+        &mut self,
+        cell: &'a Cell<VarReg>,
+        var: &'a Rc<Var>,
+        term_loc: GenContext,
+        is_exposed: bool,
+        target: &mut Vec<Target>,
+    ) {
+        if is_exposed || self.get_var_count(var.as_ref()) > 1 {
+            self.marker.mark_var(var.clone(), Level::Deep, cell, term_loc, target);
+        } else {
+            Self::add_or_increment_void_instr(target);
+        }
+    }
+
+    fn subterm_to_instr<Target: CompilationTarget<'a>>(
         &mut self,
         subterm: &'a Term,
         term_loc: GenContext,
         is_exposed: bool,
         target: &mut Vec<Target>,
-    ) where
-        Target: CompilationTarget<'a>,
-    {
+    ) {
         match subterm {
             &Term::AnonVar if is_exposed => {
-                self.marker.mark_anon_var(Level::Deep, term_loc, target)
+                self.marker.mark_anon_var(Level::Deep, term_loc, target);
+            }
+            &Term::AnonVar => {
+                Self::add_or_increment_void_instr(target);
             }
-            &Term::AnonVar => Self::add_or_increment_void_instr(target),
             &Term::Cons(ref cell, _, _) | &Term::Clause(ref cell, _, _, _) => {
-                self.marker
-                    .mark_non_var(Level::Deep, term_loc, cell, target);
+                self.marker.mark_non_var(Level::Deep, term_loc, cell, target);
                 target.push(Target::clause_arg_to_instr(cell.get()));
             }
             &Term::Constant(_, ref constant) => {
-                target.push(Target::constant_subterm(constant.clone()))
+                target.push(Target::constant_subterm(constant.clone()));
             }
             &Term::Var(ref cell, ref var) => {
-                if is_exposed || self.get_var_count(var) > 1 {
-                    self.marker
-                        .mark_var(var.clone(), Level::Deep, cell, term_loc, target);
-                } else {
-                    Self::add_or_increment_void_instr(target);
-                }
+                self.deep_var_instr(cell, var, term_loc, is_exposed, target);
             }
         };
     }
 
-    fn compile_target<Target, Iter>(
+     fn compile_target<Target, Iter>(
         &mut self,
         iter: Iter,
         term_loc: GenContext,
@@ -223,6 +235,13 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
 
         for term in iter {
             match term {
+                TermRef::AnonVar(lvl @ Level::Shallow) => {
+                    if let GenContext::Head = term_loc {
+                        self.marker.advance_arg();
+                    } else {
+                        self.marker.mark_anon_var(lvl, term_loc, &mut target);
+                    }
+                }
                 TermRef::Clause(lvl, cell, ct, terms) => {
                     self.marker.mark_non_var(lvl, term_loc, cell, &mut target);
                     target.push(Target::to_structure(ct, terms.len(), cell.get()));
@@ -238,15 +257,22 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
                     self.subterm_to_instr(head, term_loc, is_exposed, &mut target);
                     self.subterm_to_instr(tail, term_loc, is_exposed, &mut target);
                 }
+                TermRef::Constant(lvl @ Level::Shallow, cell, Constant::String(ref string)) => {
+                    self.marker.mark_non_var(lvl, term_loc, cell, &mut target);
+                    target.push(Target::to_pstr(lvl, string.to_string(), cell.get(), false));
+                }
                 TermRef::Constant(lvl @ Level::Shallow, cell, constant) => {
                     self.marker.mark_non_var(lvl, term_loc, cell, &mut target);
                     target.push(Target::to_constant(lvl, constant.clone(), cell.get()));
                 }
-                TermRef::AnonVar(lvl @ Level::Shallow) => {
-                    if let GenContext::Head = term_loc {
-                        self.marker.advance_arg();
+                TermRef::PartialString(lvl, cell, string, tail) => {
+                    self.marker.mark_non_var(lvl, term_loc, cell, &mut target);
+
+                    if let Some(tail) = tail {
+                        target.push(Target::to_pstr(lvl, string, cell.get(), true));
+                        self.subterm_to_instr(tail, term_loc, is_exposed, &mut target);
                     } else {
-                        self.marker.mark_anon_var(lvl, term_loc, &mut target);
+                        target.push(Target::to_pstr(lvl, string, cell.get(), false));
                     }
                 }
                 TermRef::Var(lvl @ Level::Shallow, cell, ref var) if var.as_str() == "!" => {
@@ -265,14 +291,13 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
                         }
                     }
 
-                    self.marker
-                        .mark_var(var.clone(), lvl, cell, term_loc, &mut target);
+                    self.marker.mark_var(var.clone(), lvl, cell, term_loc, &mut target);
                 }
                 TermRef::Var(lvl @ Level::Shallow, cell, var) => {
-                    self.marker
-                        .mark_var(var.clone(), lvl, cell, term_loc, &mut target)
+                    self.marker.mark_var(var.clone(), lvl, cell, term_loc, &mut target);
+                }
+                _ => {
                 }
-                _ => {}
             };
         }
 
@@ -281,11 +306,11 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
 
     fn collect_var_data(&mut self, mut iter: ChunkedIterator<'a>) -> ConjunctInfo<'a> {
         let mut vs = VariableFixtures::new();
-        
+
         while let Some((chunk_num, lt_arity, chunked_terms)) = iter.next() {
             for (i, chunked_term) in chunked_terms.iter().enumerate() {
                 let term_loc = match chunked_term {
-                    &ChunkedTerm::HeadClause(..) =>                       
+                    &ChunkedTerm::HeadClause(..) =>
                         GenContext::Head,
                     &ChunkedTerm::BodyTerm(_) => {
                         if i < chunked_terms.len() - 1 {
@@ -332,7 +357,9 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
                 &mut ControlInstruction::CallClause(_, _, _, ref mut last_call, _) => {
                     *last_call = true
                 }
-                &mut ControlInstruction::JmpBy(_, _, _, ref mut last_call) => *last_call = true,
+                &mut ControlInstruction::JmpBy(_, _, _, ref mut last_call) => {
+                    *last_call = true
+                }
                 &mut ControlInstruction::Proceed => {}
                 _ => dealloc_index += 1,
             },
@@ -352,33 +379,42 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
     ) -> Result<(), ParserError> {
         match ct {
             &InlinedClauseType::CompareNumber(cmp, ..) => {
-                if let &Term::Var(ref vr, ref name) = terms[0].as_ref() {
-                    self.mark_non_callable(name.clone(), 2, term_loc, vr, code);
-                }
-
-                if let &Term::Var(ref vr, ref name) = terms[1].as_ref() {
-                    self.mark_non_callable(name.clone(), 2, term_loc, vr, code);
-                }
+                self.marker.reset_arg(2);
 
                 let (mut lcode, at_1) = self.call_arith_eval(terms[0].as_ref(), 1)?;
                 let (mut rcode, at_2) = self.call_arith_eval(terms[1].as_ref(), 2)?;
 
+                let at_1 =
+                    if let &Term::Var(ref vr, ref name) = terms[0].as_ref() {
+                        ArithmeticTerm::Reg(
+                            self.mark_non_callable(name.clone(), 1, term_loc, vr, code)
+                        )
+                    } else {
+                        at_1.unwrap_or(interm!(1))
+                    };
+
+                let at_2 =
+                    if let &Term::Var(ref vr, ref name) = terms[1].as_ref() {
+                        ArithmeticTerm::Reg(
+                            self.mark_non_callable(name.clone(), 2, term_loc, vr, code)
+                        )
+                    } else {
+                        at_2.unwrap_or(interm!(2))
+                    };
+
                 code.append(&mut lcode);
                 code.append(&mut rcode);
 
-                code.push(compare_number_instr!(
-                    cmp,
-                    at_1.unwrap_or(interm!(1)),
-                    at_2.unwrap_or(interm!(2))
-                ));
+                code.push(compare_number_instr!(cmp, at_1, at_2));
             }
             &InlinedClauseType::IsAtom(..) => match terms[0].as_ref() {
-                &Term::Constant(_, Constant::Char(_))
-                | &Term::Constant(_, Constant::EmptyList)
-                | &Term::Constant(_, Constant::Atom(..)) => {
+                &Term::Constant(_, Constant::Char(_)) |
+                &Term::Constant(_, Constant::EmptyList) |
+                &Term::Constant(_, Constant::Atom(..)) => {
                     code.push(succeed!());
                 }
                 &Term::Var(ref vr, ref name) => {
+                    self.marker.reset_arg(1);
                     let r = self.mark_non_callable(name.clone(), 1, term_loc, vr, code);
                     code.push(is_atom!(r));
                 }
@@ -394,6 +430,7 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
                     code.push(succeed!());
                 }
                 &Term::Var(ref vr, ref name) => {
+                    self.marker.reset_arg(1);
                     let r = self.mark_non_callable(name.clone(), 1, term_loc, vr, code);
                     code.push(is_atomic!(r));
                 }
@@ -403,6 +440,7 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
                     code.push(succeed!());
                 }
                 &Term::Var(ref vr, ref name) => {
+                    self.marker.reset_arg(1);
                     let r = self.mark_non_callable(name.clone(), 1, term_loc, vr, code);
                     code.push(is_compound!(r));
                 }
@@ -415,6 +453,7 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
                     code.push(succeed!());
                 }
                 &Term::Var(ref vr, ref name) => {
+                    self.marker.reset_arg(1);
                     let r = self.mark_non_callable(name.clone(), 1, term_loc, vr, code);
                     code.push(is_rational!(r));
                 }
@@ -427,6 +466,7 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
                     code.push(succeed!());
                 }
                 &Term::Var(ref vr, ref name) => {
+                    self.marker.reset_arg(1);
                     let r = self.mark_non_callable(name.clone(), 1, term_loc, vr, code);
                     code.push(is_float!(r));
                 }
@@ -434,23 +474,12 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
                     code.push(fail!());
                 }
             },
-            &InlinedClauseType::IsString(..) => match terms[0].as_ref() {
-                &Term::Constant(_, Constant::String(_)) => {
-                    code.push(succeed!());
-                }
-                &Term::Var(ref vr, ref name) => {
-                    let r = self.mark_non_callable(name.clone(), 1, term_loc, vr, code);
-                    code.push(is_string!(r));
-                }
-                _ => {
-                    code.push(fail!());
-                }
-            },
             &InlinedClauseType::IsNonVar(..) => match terms[0].as_ref() {
                 &Term::AnonVar => {
                     code.push(fail!());
                 }
                 &Term::Var(ref vr, ref name) => {
+                    self.marker.reset_arg(1);
                     let r = self.mark_non_callable(name.clone(), 1, term_loc, vr, code);
                     code.push(is_nonvar!(r));
                 }
@@ -459,11 +488,12 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
                 }
             },
             &InlinedClauseType::IsInteger(..) => match terms[0].as_ref() {
-                &Term::Constant(_, Constant::CharCode(_))
-                | &Term::Constant(_, Constant::Integer(_)) => {
+                &Term::Constant(_, Constant::Integer(_)) |
+                &Term::Constant(_, Constant::Fixnum(_)) => {
                     code.push(succeed!());
                 }
                 &Term::Var(ref vr, ref name) => {
+                    self.marker.reset_arg(1);
                     let r = self.mark_non_callable(name.clone(), 1, term_loc, vr, code);
                     code.push(is_integer!(r));
                 }
@@ -479,17 +509,11 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
                     code.push(succeed!());
                 }
                 &Term::Var(ref vr, ref name) => {
+                    self.marker.reset_arg(1);
                     let r = self.mark_non_callable(name.clone(), 1, term_loc, vr, code);
                     code.push(is_var!(r));
                 }
             },
-            &InlinedClauseType::IsPartialString(..) => match terms[0].as_ref() {
-                &Term::Var(ref vr, ref name) => {
-                    let r = self.mark_non_callable(name.clone(), 1, term_loc, vr, code);
-                    code.push(is_partial_string!(r));
-                }
-                _ => code.push(fail!()),
-            },
         }
 
         Ok(())
@@ -500,7 +524,7 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
         term: &'a Term,
         target_int: usize,
     ) -> Result<ArithCont, ArithmeticError> {
-        let mut evaluator = ArithmeticEvaluator::new(self.marker.bindings(), target_int);
+        let mut evaluator = ArithmeticEvaluator::new(&self.marker.bindings(), target_int);
         evaluator.eval(term)
     }
 
@@ -514,36 +538,27 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
         let (mut acode, at) = self.call_arith_eval(terms[1].as_ref(), 1)?;
         code.append(&mut acode);
 
-        Ok(match terms[0].as_ref() {
+        self.marker.reset_arg(2);
+
+        match terms[0].as_ref() {
             &Term::Var(ref vr, ref name) => {
                 let mut target = vec![];
 
-                self.marker.reset_arg(2);
-                self.marker
-                    .mark_var(name.clone(), Level::Shallow, vr, term_loc, &mut target);
+                self.marker.mark_var(name.clone(), Level::Shallow, vr, term_loc, &mut target);
 
                 if !target.is_empty() {
                     code.extend(target.into_iter().map(Line::Query));
                 }
-
-                if use_default_call_policy {
-                    code.push(is_call_by_default!(temp_v!(1), at.unwrap_or(interm!(1))))
-                } else {
-                    code.push(is_call!(temp_v!(1), at.unwrap_or(interm!(1))))
-                }
             }
-            &Term::Constant(_, ref c @ Constant::Integer(_)) => {
+            &Term::Constant(_, ref c @ Constant::Integer(_)) |
+            &Term::Constant(_, ref c @ Constant::Fixnum(_)) => {
                 code.push(Line::Query(put_constant!(
                     Level::Shallow,
                     c.clone(),
                     temp_v!(1)
                 )));
 
-                if use_default_call_policy {
-                    code.push(is_call_by_default!(temp_v!(1), at.unwrap_or(interm!(1))))
-                } else {
-                    code.push(is_call!(temp_v!(1), at.unwrap_or(interm!(1))))
-                }
+                self.marker.advance_arg();
             }
             &Term::Constant(_, ref c @ Constant::Float(_)) => {
                 code.push(Line::Query(put_constant!(
@@ -552,11 +567,7 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
                     temp_v!(1)
                 )));
 
-                if use_default_call_policy {
-                    code.push(is_call_by_default!(temp_v!(1), at.unwrap_or(interm!(1))))
-                } else {
-                    code.push(is_call!(temp_v!(1), at.unwrap_or(interm!(1))))
-                }
+                self.marker.advance_arg();
             }
             &Term::Constant(_, ref c @ Constant::Rational(_)) => {
                 code.push(Line::Query(put_constant!(
@@ -565,13 +576,27 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
                     temp_v!(1)
                 )));
 
-                if use_default_call_policy {
-                    code.push(is_call_by_default!(temp_v!(1), at.unwrap_or(interm!(1))))
-                } else {
-                    code.push(is_call!(temp_v!(1), at.unwrap_or(interm!(1))))
-                }
+                self.marker.advance_arg();
             }
-            _ => code.push(fail!()),
+            _ => {
+                code.push(fail!());
+                return Ok(());
+            }
+        }
+
+        let at =
+            if let &Term::Var(ref vr, ref name) = terms[1].as_ref() {
+                ArithmeticTerm::Reg(
+                    self.mark_non_callable(name.clone(), 2, term_loc, vr, code)
+                )
+            } else {
+                at.unwrap_or(interm!(1))
+            };
+
+        Ok(if use_default_call_policy {
+            code.push(is_call_by_default!(temp_v!(1), at));
+        } else {
+            code.push(is_call!(temp_v!(1), at));
         })
     }
 
@@ -694,6 +719,7 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
             head: (_, ref args, ref p1),
             ref clauses,
         } = rule;
+
         let mut code = Vec::new();
 
         self.marker.reset_at_head(args);
@@ -715,39 +741,31 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
         let iter = ChunkedIterator::from_rule_body(p1, clauses);
         self.compile_seq(iter, &conjunct_info, &mut code, false)?;
 
-        conjunct_info.mark_unsafe_vars(unsafe_var_marker, &self.marker, &mut code);        
+        conjunct_info.mark_unsafe_vars(unsafe_var_marker, &mut code);
 
         Self::compile_cleanup(&mut code, &conjunct_info, clauses.last().unwrap_or(p1));
         Ok(code)
     }
 
     fn mark_unsafe_fact_vars(&self, fact: &mut CompiledFact) -> UnsafeVarMarker {
-        let mut unsafe_vars = IndexMap::new();
-
-        for var_status in self.marker.bindings().values() {
-            unsafe_vars.insert(var_status.as_reg_type(), false);
-        }
+        let mut safe_vars = IndexSet::new();
 
         for fact_instr in fact.iter_mut() {
             match fact_instr {
-                &mut FactInstruction::UnifyValue(reg) => {
-                    if let Some(found) = unsafe_vars.get_mut(&reg) {
-                        if !*found {
-                            *found = true;
-                            *fact_instr = FactInstruction::UnifyLocalValue(reg);
-                        }
+                &mut FactInstruction::UnifyValue(r) => {
+                    if !safe_vars.contains(&r) {
+                        *fact_instr = FactInstruction::UnifyLocalValue(r);
+                        safe_vars.insert(r);
                     }
                 }
-                &mut FactInstruction::UnifyVariable(reg) => {
-                    if let Some(found) = unsafe_vars.get_mut(&reg) {
-                        *found = true;
-                    }
+                &mut FactInstruction::UnifyVariable(r) => {
+                    safe_vars.insert(r);
                 }
                 _ => {}
-            };
+            }
         }
 
-        UnsafeVarMarker { unsafe_vars }
+        UnsafeVarMarker::from_safe_vars(safe_vars)
     }
 
     pub fn compile_fact<'b: 'a>(&mut self, term: &'b Term) -> Code {
@@ -812,7 +830,7 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
         let iter = ChunkedIterator::from_term_sequence(query);
         self.compile_seq(iter, &conjunct_info, &mut code, true)?;
 
-        conjunct_info.mark_unsafe_vars(UnsafeVarMarker::new(), &self.marker, &mut code);
+        conjunct_info.mark_unsafe_vars(UnsafeVarMarker::new(), &mut code);
 
         if let Some(query_term) = query.last() {
             Self::compile_cleanup(&mut code, &conjunct_info, query_term);
@@ -867,7 +885,7 @@ impl<'a, TermMarker: Allocator<'a>> CodeGenerator<TermMarker> {
         clauses: &'b [PredicateClause],
     ) -> Result<Code, ParserError> {
         let mut code_body = Vec::new();
-        let mut code_offsets = CodeOffsets::new(self.flags);
+        let mut code_offsets = CodeOffsets::new();
 
         let num_clauses = clauses.len();
 

src/debray_allocator.rs

@@ -1,17 +1,18 @@
-use indexmap::IndexMap;
+use crate::indexmap::IndexMap;
 
-use prolog_parser::ast::*;
+use crate::prolog_parser::ast::*;
 
-use crate::prolog::allocator::*;
-use crate::prolog::fixtures::*;
-use crate::prolog::forms::*;
-use crate::prolog::machine::machine_indices::*;
-use crate::prolog::targets::*;
+use crate::allocator::*;
+use crate::fixtures::*;
+use crate::forms::*;
+use crate::machine::machine_indices::*;
+use crate::targets::*;
 
 use std::cell::Cell;
 use std::collections::BTreeSet;
 use std::rc::Rc;
 
+#[derive(Debug)]
 pub struct DebrayAllocator {
     bindings: IndexMap<Rc<Var>, VarData>,
     arg_c: usize,
@@ -292,7 +293,9 @@ impl<'a> Allocator<'a> for DebrayAllocator {
 
                 (pr, true)
             }
-            r => (r, false),
+            r => {
+                (r, false)
+            }
         };
 
         self.mark_reserved_var(var, lvl, cell, term_loc, target, r, is_new_var);

src/examples/bimetatrans/README.md

@@ -0,0 +1,219 @@
+### BiMetaTrans 1.0
+
+BiMetaTrans(Prolog, RuleML) is a bidirectional translator capable of
+parsing and generating a well-formed sublanguage of RuleML/XML to/from
+a metalogical encoding of our own design called Prolog/'$V'. For later
+ease of reference:
+
+* Prolog/'$V' stands for "Metalogic Prolog with variable-as-'$V'-term encoding"
+* RuleML/XML stands for "RuleML in XML with any kind of rendering"
+* RuleML/xmL stands for "RuleML in minified XML"
+* RuleML/Xml stands for "RuleML in indented XML"
+
+"Minified XML" refers to XML with only necessary whitespace, between
+element names and attributes, and pairs of attributes, with all
+indentation stripped out. "Indented XML" contains indentation and
+newlines, and is usually formatted for human readers.
+
+The specification of Prolog/'$V', and of the NafHornlogEq sublanguage
+of RuleML/XML targeted by BiMetaTrans, is contained in the preprint
+[Invertible Bidirectional Metalogical Translation Between Prolog and
+RuleML/XML for Knowledge Representation and
+Querying](http://ruleml.org/papers/RuleMLXMLBiDirTransScryer.pdf) and
+its accompanying talk
+[slides](http://ruleml.org/talks/RuleMLXMLBiDirTransScryer-talk.pdf). The
+preprint and talk also describe the implementation of BiMetaTrans
+found here, and outlines a strategy for proving the invertibility of
+BiMetaTrans.
+
+BiMetaTrans exports a single public predicate subsuming its user
+API, `parse_ruleml/3`. It has two modes, each corresponding to a single
+direction of translation:
+
+```
+parse_ruleml(+AssertItems, +QueryItems, ?XML)    (Prolog->RuleML)
+parse_ruleml(?AssertItems, ?QueryItems, +XML)    (RuleML->Prolog)
+```
+
+The modes constrain the inputs to fit one of two patterns, the
+first where AssertItems and QueryItems are instantiated and XML is
+possibly a variable, and conversely for the second. Instantiated
+inputs are expected to be ground, meaning they should not contain
+free variables.
+
+We explore several examples of its use in Scryer Prolog.
+
+Loading BiMetaTrans from the Scryer REPL:
+
+```
+?- use_module('src/examples/bimetatrans/bimetatrans').
+```
+
+Using `write/1` to print the string to standard output, capturing the
+`Prolog->RuleML` direction (`write/1` is used because it does not
+print strings with escape characters, ie., `\"` for double quote):
+
+```
+?- parse_ruleml([people('Alex',male),people('Alex',female),people('Siri',female)], [], XML),
+   write(XML).
+"<Assert mapClosure="universal"><Atom><Rel>people</Rel><Ind>Alex</Ind><Data iso:type="symbol">male</Data></Atom><Atom><Rel>people</Rel><Ind>Alex</Ind><Data iso:type="symbol">female</Data></Atom><Atom><Rel>people</Rel><Ind>Siri</Ind><Data iso:type="symbol">female</Data></Atom></Assert>"   XML = "<Assert mapClosure= ...".
+```
+
+Note that the XML input can contain extraneous whitespace and
+indentation while generated XML never does (ie., the XML generated by
+BiMetaTrans is always Ruleml/xmL). `\` is used to continue ISO Prolog
+strings to the next line but is never stored to the string by the
+Prolog reader.
+
+Performing the inverse translation of the previous example
+(`RuleML->Prolog`), in RuleML/Xml:
+
+```
+?- parse_ruleml(AssertItems, QueryItems,
+                "<Assert mapClosure=\"universal\">\
+                   <Atom>\
+                           <Rel>people</Rel>\
+                           <Ind>Alex</Ind>\
+                           <Data iso:type=\"symbol\">male</Data>\
+                   </Atom>\
+                   <Atom>\
+                           <Rel>people</Rel>\
+                           <Ind>Alex</Ind>\
+                           <Data iso:type=\"symbol\">female</Data>\
+                   </Atom>\
+                   <Atom>\
+                           <Rel>people</Rel>\
+                           <Ind>Siri</Ind>\
+                           <Data iso:type=\"symbol\">female</Data>\
+                   </Atom>\
+                </Assert>").
+   AssertItems = [people('Alex',male),people('Alex',female),people('Siri',female)], QueryItems = [].
+```
+
+Double quote characters within strings must be escaped as in
+`\"`. Non-empty AssertItems and QueryItems lists generated to
+RuleML/xmL simultaneously:
+
+```
+?- parse_ruleml([a(item), b(item), c(item)], [(?- p, q, r(1), s(-2.222342432), t("attached")), (?- u, v('$V'(q)))], XML),
+   write(XML).
+"<Assert mapClosure="universal"><Atom><Rel>a</Rel><Data iso:type="symbol">item</Data></Atom><Atom><Rel>b</Rel><Data iso:type="symbol">item</Data></Atom><Atom><Rel>c</Rel><Data iso:type="symbol">item</Data></Atom></Assert><Query closure="existential"><And><Atom><Rel>p</Rel></Atom><Atom><Rel>q</Rel></Atom><Atom><Rel>r</Rel><Data iso:type="number">1</Data></Atom><Atom><Rel>s</Rel><Data iso:type="number">-2.222342432</Data></Atom><Atom><Rel>t</Rel><Data iso:type="string">"attached"</Data></Atom></And></Query><Query closure="existential"><And><Atom><Rel>u</Rel></Atom><Atom><Rel>v</Rel><Var>q</Var></Atom></And></Query>"   XML = "<Assert mapClosure= ...".
+```
+
+To insert escape characters into the printed RuleML/xmL, we use
+`writeq/1` in place of `write/1`:
+
+```
+?- parse_ruleml([a(item), b(item), c(item)], [(?- p, q, r(1), s(-2.222342432), t("attached")), (?- u, v('$V'(q)))], XML),
+   writeq(XML).
+"<Assert mapClosure=\"universal\"><Atom><Rel>a</Rel><Data iso:type=\"symbol\">item</Data></Atom><Atom><Rel>b</Rel><Data iso:type=\"symbol\">item</Data></Atom><Atom><Rel>c</Rel><Data iso:type=\"symbol\">item</Data></Atom></Assert><Query closure=\"existential\"><And><Atom><Rel>p</Rel></Atom><Atom><Rel>q</Rel></Atom><Atom><Rel>r</Rel><Data iso:type=\"number\">1</Data></Atom><Atom><Rel>s</Rel><Data iso:type=\"number\">-2.222342432</Data></Atom><Atom><Rel>t</Rel><Data iso:type=\"string\">\"attached\"</Data></Atom></And></Query><Query closure=\"existential\"><And><Atom><Rel>u</Rel></Atom><Atom><Rel>v</Rel><Var>q</Var></Atom></And></Query>"   XML = "<Assert mapClosure= ...".
+```
+
+XML can be pretty printed using a [free online XML pretty
+printer](https://codebeautify.org/xmlviewer), as here:
+
+```
+<Assert mapClosure=\"universal\">
+	<Atom>
+		<Rel>a</Rel>
+		<Data iso:type=\"symbol\">item</Data>
+	</Atom>
+	<Atom>
+		<Rel>b</Rel>
+		<Data iso:type=\"symbol\">item</Data>
+	</Atom>
+	<Atom>
+		<Rel>c</Rel>
+		<Data iso:type=\"symbol\">item</Data>
+	</Atom>
+</Assert>
+<Query closure=\"existential\">
+	<And>
+		<Atom>
+			<Rel>p</Rel>
+		</Atom>
+		<Atom>
+			<Rel>q</Rel>
+		</Atom>
+		<Atom>
+			<Rel>r</Rel>
+			<Data iso:type=\"number\">1</Data>
+		</Atom>
+		<Atom>
+			<Rel>s</Rel>
+			<Data iso:type=\"number\">-2.222342432</Data>
+		</Atom>
+		<Atom>
+			<Rel>t</Rel>
+			<Data iso:type=\"string\">\"attached\"</Data>
+		</Atom>
+	</And>
+</Query>
+<Query closure=\"existential\">
+	<And>
+		<Atom>
+			<Rel>u</Rel>
+		</Atom>
+		<Atom>
+			<Rel>v</Rel>
+			<Var>q</Var>
+		</Atom>
+	</And>
+</Query>
+```
+
+The AssertItems and QueryItems lists can then be recovered using this
+RuleML/Xml string, with the `\` character added to the end of each
+line:
+
+```
+?- parse_ruleml(AssertItems, QueryItems,
+                "<Assert mapClosure=\"universal\">\
+                    <Atom>\
+                        <Rel>a</Rel>\
+                        <Data iso:type=\"symbol\">item</Data>\
+                    </Atom>\
+                    <Atom>\
+                        <Rel>b</Rel>\
+                        <Data iso:type=\"symbol\">item</Data>\
+                    </Atom>\
+                    <Atom>\
+                        <Rel>c</Rel>\
+                        <Data iso:type=\"symbol\">item</Data>\
+                    </Atom>\
+                </Assert>\
+                <Query closure=\"existential\">\
+                    <And>\
+                        <Atom>\
+                            <Rel>p</Rel>\
+                        </Atom>\
+                        <Atom>\
+                            <Rel>q</Rel>\
+                        </Atom>\
+                        <Atom>\
+                            <Rel>r</Rel>\
+                            <Data iso:type=\"number\">1</Data>\
+                        </Atom>\
+                        <Atom>\
+                            <Rel>s</Rel>\
+                            <Data iso:type=\"number\">-2.222342432</Data>\
+                        </Atom>\
+                        <Atom>\
+                            <Rel>t</Rel>\
+                            <Data iso:type=\"string\">\"attached\"</Data>\
+                        </Atom>\
+                    </And>\
+                </Query>\
+                <Query closure=\"existential\">\
+                    <And>\
+                        <Atom>\
+                            <Rel>u</Rel>\
+                        </Atom>\
+                        <Atom>\
+                            <Rel>v</Rel>\
+                            <Var>q</Var>\
+                        </Atom>\
+                    </And>\
+                </Query>").
+   AssertItems = [a(item),b(item),c(item)], QueryItems = [(?-p,q,r(1),s(-2.222342432),t("attached")),(?-u,v('$V'(q)))].
+```

src/examples/domain.pl

@@ -22,7 +22,6 @@ verify_attributes(Var, Other, Goals) :-
                 (   Els = [] ->             % exactly one element
                     Goals = [Other=El]      % implied binding
                 ;   Goals = [],
-		    put_atts(Other, -dom(_)),
                     put_atts(Other, dom(Dc))% rescue intersection
                 )
             ;   Goals = [],

src/examples/echo_server.pl

@@ -0,0 +1,31 @@
+:- module(echo_server, [echo_server/0,
+                        echo_server/1]).
+
+:- use_module(library(format)).
+:- use_module(library(sockets)).
+
+
+echo_server :-
+    echo_server('127.0.0.1').
+
+
+echo_server(Addr) :-
+    socket_server_open(Addr:Port, ServerSocket),
+    format("echo_server: connection opened at ~w:~d~n", [Addr, Port]),
+    socket_server_accept(ServerSocket, Client, Stream, [eof_action(eof_code)]),
+    format("echo_server: connection accepted from ~a~n", [Client]),
+    !,
+    echo_loop(Stream),
+    socket_server_close(ServerSocket).
+
+
+echo_loop(Stream) :-
+    read_term(Stream, Term, []),
+    (  Term == end_of_file ->
+       true
+    ;
+       format("received: ~w~n", [Term]),
+       !,
+       echo_loop(Stream)
+    ).
+

src/examples/least_time.pl

@@ -0,0 +1,57 @@
+/*  least_time.pl
+ *
+ *  By Mark Thom, 2020
+ *
+ *  find_min_time/2 solves a problem sometimes posed in the first round
+ *  of Google interviews: given a time of day in 24 H format, what is the
+ *  lexicographically least permutation of the time that is itself a
+ *  valid time in 24 H format?
+ *
+ *  Full generality is achieved using the reif library.
+ */
+
+:- module(least_time, [find_min_time/2,
+		               write_time_nl/1]).
+
+
+:- use_module(library(dcgs)).
+:- use_module(library(format)).
+:- use_module(library(lists)).
+:- use_module(library(reif)).
+
+
+permutation([], []).
+permutation([X|Xs], Ys) :-
+    permutation(Xs, Yss),
+    select(X, Ys, Yss).
+
+
+valid_time([H1,H2,M1,M2], T) :-
+    memberd_t(H1, [0,1,2], TH1),
+    memberd_t(H2, [0,1,2,3,4,5,6,7,8,9], TH2),
+    memberd_t(M1, [0,1,2,3,4,5], TM1),
+    memberd_t(M2, [0,1,2,3,4,5,6,7,8,9], TM2),
+    (  maplist(=(true), [TH1, TH2, TM1, TM2]) ->
+       (  H1 =:= 2 ->
+	      (  H2 =< 3 ->
+	         T = true
+	      ;  T = false
+	      )
+       ;  T = true
+       )
+    ;  T = false
+    ).
+
+
+permuted_times(Time, PermutedTimes) :-
+    setof(P, permutation(Time, P), PermutedTimes0),
+    tfilter(valid_time, PermutedTimes0, PermutedTimes).
+
+
+find_min_time(Time, Min) :-
+    valid_time(Time, true),
+    permuted_times(Time, [Min|_]).
+
+
+write_time_nl(Time) :-
+    format("\"~w~w:~w~w\"~n", Time).

src/examples/plres.pl

@@ -31,6 +31,7 @@
 
 :- use_module(library(dcgs)).
 :- use_module(library(dif)).
+:- use_module(library(format)).
 :- use_module(library(lists)).
 
 pl_resolution(Clauses0, Chain) :-

src/examples/utf8.pl

@@ -0,0 +1,31 @@
+:- use_module(library(charsio)).
+:- use_module(library(lists)).
+
+:- initialization(unit_test).
+
+unit_test :-
+  chars_utf8bytes("a£\x2124\", Bs),
+  Bs = [97, 194, 163, 226, 132, 164],
+  chars_utf8bytes(Cs, Bs),
+  Cs = "a£\x2124\".
+
+write_f :-
+  open('x.txt', write, Stream, [type(binary)]),
+  F = put_byte(Stream),
+  chars_utf8bytes("£\x2124\\x2764\\x1F496\\n", Bs),
+  maplist(F, Bs),
+  close(Stream).
+
+get_bytes(Stream, Res) :- get_bytes(Stream, [], Res).
+get_bytes(Stream, Acc, Res) :-
+  get_byte(Stream, B),
+  (B =:= -1 ->
+    reverse(Acc, Res)
+  ; get_bytes(Stream, [B|Acc], Res)).
+
+read_f :-
+  open('x.txt', read, Stream, [type(binary)]),
+  get_bytes(Stream, Bs),
+  chars_utf8bytes(Cs, Bs),
+  write(Cs),
+  close(Stream).

src/fixtures.rs

@@ -1,11 +1,10 @@
-use prolog_parser::ast::*;
+use crate::prolog_parser::ast::*;
 
-use crate::prolog::allocator::*;
-use crate::prolog::forms::*;
-use crate::prolog::instructions::*;
-use crate::prolog::iterators::*;
+use crate::forms::*;
+use crate::instructions::*;
+use crate::iterators::*;
 
-use indexmap::{IndexMap, IndexSet};
+use crate::indexmap::{IndexMap, IndexSet};
 
 use std::cell::Cell;
 use std::collections::BTreeSet;
@@ -14,6 +13,7 @@ use std::rc::Rc;
 use std::vec::Vec;
 
 // labeled with chunk numbers.
+#[derive(Debug)]
 pub enum VarStatus {
     Perm(usize),
     Temp(usize, TempVarData), // Perm(chunk_num) | Temp(chunk_num, _)
@@ -23,6 +23,7 @@ pub type OccurrenceSet = BTreeSet<(GenContext, usize)>;
 
 // Perm: 0 initially, a stack register once processed.
 // Temp: labeled with chunk_num and temp offset (unassigned if 0).
+#[derive(Debug)]
 pub enum VarData {
     Perm(usize),
     Temp(usize, usize, TempVarData),
@@ -37,6 +38,7 @@ impl VarData {
     }
 }
 
+#[derive(Debug)]
 pub struct TempVarData {
     pub last_term_arity: usize,
     pub use_set: OccurrenceSet,
@@ -80,6 +82,7 @@ impl TempVarData {
 
 type VariableFixture<'a> = (VarStatus, Vec<&'a Cell<VarReg>>);
 
+#[derive(Debug)]
 pub struct VariableFixtures<'a>{
     perm_vars: IndexMap<Rc<Var>, VariableFixture<'a>>,
     last_chunk_temp_vars: IndexSet<Rc<Var>>
@@ -91,7 +94,7 @@ impl<'a> VariableFixtures<'a> {
             perm_vars: IndexMap::new(),
             last_chunk_temp_vars: IndexSet::new()
         }
-                          
+
     }
 
     pub fn insert(&mut self, var: Rc<Var>, vs: VariableFixture<'a>) {
@@ -249,68 +252,69 @@ impl<'a> VariableFixtures<'a> {
     }
 }
 
+#[derive(Debug)]
 pub struct UnsafeVarMarker {
-    pub unsafe_vars: IndexMap<RegType, bool>,
+    pub unsafe_vars: IndexMap<RegType, usize>,
+    pub safe_vars: IndexSet<RegType>,
 }
 
 impl UnsafeVarMarker {
     pub fn new() -> Self {
         UnsafeVarMarker {
             unsafe_vars: IndexMap::new(),
+            safe_vars: IndexSet::new()
         }
     }
 
-    pub fn record_unsafe_vars<'a, Alloc: Allocator<'a>>(
-        &mut self,
-        fixtures: &VariableFixtures,
-        marker: &Alloc
-    ) {
-        for &(_, ref cb) in fixtures.values() {           
-            if let Some(index) = cb.first() {
-                if !self.unsafe_vars.contains_key(&index.get().norm()) {
-                    self.unsafe_vars.insert(index.get().norm(), false);
-                }
-            }
-        }
-
-        for var in fixtures.last_chunk_temp_vars.iter().cloned() {
-            let r = marker.get(var);
-            self.unsafe_vars.insert(r, false);
+    pub fn from_safe_vars(safe_vars: IndexSet<RegType>) -> Self {
+        UnsafeVarMarker {
+            unsafe_vars: IndexMap::new(),
+            safe_vars
         }
     }
 
-    pub fn mark_safe_vars(&mut self, query_instr: &QueryInstruction) {
+    pub fn mark_safe_vars(&mut self, query_instr: &QueryInstruction) -> bool {
         match query_instr {
-            QueryInstruction::PutVariable(RegType::Temp(r), _) => {
-                if let Some(found) = self.unsafe_vars.get_mut(&RegType::Temp(*r)) {
-                    *found = true;
-                }
+            &QueryInstruction::PutVariable(r @ RegType::Temp(_), _)
+          | &QueryInstruction::SetVariable(r) =>  {
+                self.safe_vars.insert(r);
+                true
             }
-            QueryInstruction::SetVariable(reg) => {
-                if let Some(found) = self.unsafe_vars.get_mut(reg) {
-                    *found = true;
-                }
+            _ => {
+                false
+            }
+        }
+    }
+
+    pub fn mark_phase(&mut self, query_instr: &QueryInstruction, phase: usize) {
+        match query_instr {
+            &QueryInstruction::PutValue(r @ RegType::Perm(_), _)
+          | &QueryInstruction::SetValue(r) => {
+                let p = self.unsafe_vars.entry(r).or_insert(0);
+                *p = phase;
             }
             _ => {}
         }
     }
 
-    pub fn mark_unsafe_vars(&mut self, query_instr: &mut QueryInstruction) {
+    pub fn mark_unsafe_vars(&mut self, query_instr: &mut QueryInstruction, phase: usize) {
         match query_instr {
             &mut QueryInstruction::PutValue(RegType::Perm(i), arg) => {
-                if let Some(found) = self.unsafe_vars.get_mut(&RegType::Perm(i)) {
-                    if !*found {
-                        *found = true;
+                if let Some(p) = self.unsafe_vars.swap_remove(&RegType::Perm(i)) {
+                    if p == phase {
                         *query_instr = QueryInstruction::PutUnsafeValue(i, arg);
+                        self.safe_vars.insert(RegType::Perm(i));
+                    } else {
+                        self.unsafe_vars.insert(RegType::Perm(i), p);
                     }
                 }
             }
-            &mut QueryInstruction::SetValue(reg) => {
-                if let Some(found) = self.unsafe_vars.get_mut(&reg) {
-                    if !*found {
-                        *found = true;
-                        *query_instr = QueryInstruction::SetLocalValue(reg);
-                    }
+            &mut QueryInstruction::SetValue(r) => {
+                if !self.safe_vars.contains(&r) {
+                    *query_instr = QueryInstruction::SetLocalValue(r);
+
+                    self.safe_vars.insert(r);
+                    self.unsafe_vars.remove(&r);
                 }
             }
             _ => {}

src/forms.rs

@@ -0,0 +1,705 @@
+use crate::prolog_parser::ast::*;
+use crate::prolog_parser::parser::OpDesc;
+use crate::prolog_parser::tabled_rc::*;
+
+use crate::clause_types::*;
+use crate::machine::machine_errors::*;
+use crate::machine::machine_indices::*;
+use crate::ordered_float::OrderedFloat;
+use crate::rug::{Integer, Rational};
+
+use crate::indexmap::IndexMap;
+
+use std::cell::Cell;
+use std::collections::VecDeque;
+use std::path::PathBuf;
+use std::rc::Rc;
+
+pub type PredicateKey = (ClauseName, usize); // name, arity.
+
+// vars of predicate, toplevel offset.  Vec<Term> is always a vector
+// of vars (we get their adjoining cells this way).
+pub type JumpStub = Vec<Term>;
+
+#[derive(Debug, Clone)]
+pub enum TopLevel {
+    Declaration(Declaration),
+    Fact(Term, usize, usize), // Term, line_num, col_num
+    Predicate(Predicate),
+    Query(Vec<QueryTerm>),
+    Rule(Rule, usize, usize), // Rule, line_num, col_num
+}
+
+impl TopLevel {
+    pub fn is_end_of_file_atom(&self) -> bool {
+        match self {
+            &TopLevel::Fact(Term::Constant(_, Constant::Atom(ref name, _)), ..) => {
+                return name.as_str() == "end_of_file"
+            }
+            _ => false,
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum Level {
+    Deep,
+    Root,
+    Shallow,
+}
+
+impl Level {
+    pub fn child_level(self) -> Level {
+        match self {
+            Level::Root => Level::Shallow,
+            _ => Level::Deep,
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub enum QueryTerm {
+    // register, clause type, subterms, use default call policy.
+    Clause(Cell<RegType>, ClauseType, Vec<Box<Term>>, bool),
+    BlockedCut, // a cut which is 'blocked by letters', like the P term in P -> Q.
+    UnblockedCut(Cell<VarReg>),
+    GetLevelAndUnify(Cell<VarReg>, Rc<Var>),
+    Jump(JumpStub),
+}
+
+impl QueryTerm {
+    pub fn set_default_caller(&mut self) {
+        match self {
+            &mut QueryTerm::Clause(_, _, _, ref mut use_default_cp) => *use_default_cp = true,
+            _ => {}
+        }
+    }
+
+    pub fn arity(&self) -> usize {
+        match self {
+            &QueryTerm::Clause(_, _, ref subterms, ..) => subterms.len(),
+            &QueryTerm::BlockedCut | &QueryTerm::UnblockedCut(..) => 0,
+            &QueryTerm::Jump(ref vars) => vars.len(),
+            &QueryTerm::GetLevelAndUnify(..) => 1,
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct Rule {
+    pub head: (ClauseName, Vec<Box<Term>>, QueryTerm),
+    pub clauses: Vec<QueryTerm>,
+}
+
+#[derive(Debug, Clone)]
+pub struct Predicate(pub Vec<PredicateClause>);
+
+impl Predicate {
+    #[inline]
+    pub fn new() -> Self {
+        Predicate(vec![])
+    }
+
+    #[inline]
+    pub fn clauses(self) -> Vec<PredicateClause> {
+        self.0
+    }
+
+    #[inline]
+    pub fn predicate_indicator(&self) -> Option<(ClauseName, usize)> {
+        self.0
+            .first()
+            .and_then(|clause| clause.name().map(|name| (name, clause.arity())))
+    }
+}
+
+#[derive(Debug, Clone)]
+pub enum ListingSource {
+    File(ClauseName, PathBuf), // filename, path
+    User,
+}
+
+impl ListingSource {
+    pub fn from_file_and_path(filename: ClauseName, path_buf: PathBuf) -> Self {
+        ListingSource::File(filename, path_buf)
+    }
+
+    pub fn name(&self) -> ClauseName {
+        match self {
+            ListingSource::File(ref filename, _) => filename.clone(),
+            ListingSource::User => clause_name!("[user]")
+        }
+    }
+
+    pub fn path(&self) -> PathBuf {
+        match self {
+            ListingSource::File(_, ref path) => path.clone(),
+            ListingSource::User => std::env::current_dir().unwrap(),
+        }
+    }
+}
+
+fn resolved_term_and_module(term: &Term) -> Option<(ClauseName, ClauseName)>
+{
+    match term {
+        Term::Clause(_, ref name, ref terms, _) => {
+            if name.as_str() == ":" && terms.len() == 2 {
+                let module_name = match terms[0].as_ref() {
+                    &Term::Constant(_, Constant::Atom(ref module_name, _)) => {
+                        module_name.clone()
+                    }
+                    _ => {
+                        return Some((name.owning_module(), name.clone()));
+                    }
+                };
+
+                match terms[1].as_ref() {
+                    Term::Clause(_, ref name, ..)
+                  | Term::Constant(_, Constant::Atom(ref name, ..)) => {
+                        return Some((module_name, name.clone()));
+                    }
+                    _ => {
+                    }
+                }
+
+                Some((name.owning_module(), name.clone()))
+            } else {
+                Some((name.owning_module(), name.clone()))
+            }
+        }
+        Term::Constant(_, Constant::Atom(ref name, _)) => {
+            Some((name.owning_module(), name.clone()))
+        }
+        _ => {
+            None
+        }
+    }
+}
+
+fn resolved_term_arity(term: &Term) -> usize
+{
+    match term {
+        Term::Clause(_, ref name, ref terms, _) => {
+            if name.as_str() == ":" && terms.len() == 2 {
+                match terms[0].as_ref() {
+                    &Term::Constant(_, Constant::Atom(..)) => {
+                    }
+                    _ => {
+                        return 2;
+                    }
+                }
+
+                match terms[1].as_ref() {
+                    Term::Clause(_, _, ref terms, _) => {
+                        terms.len()
+                    }
+                    Term::Constant(_, Constant::Atom(..)) => {
+                        0
+                    }
+                    _ => {
+                        2
+                    }
+                }
+            } else {
+                terms.len()
+            }
+        }
+        _ => {
+            0
+        }
+    }
+}
+
+pub trait ClauseConsistency {
+    fn is_consistent(&self, clauses: &Vec<PredicateClause>) -> bool {
+        match clauses.first() {
+            Some(ref cl) => {
+                self.name_and_module() == cl.name_and_module() && self.arity() == cl.arity()
+            }
+            None => {
+                true
+            }
+        }
+    }
+
+    fn name_and_module(&self) -> Option<(ClauseName, ClauseName)>;
+    fn arity(&self) -> usize;
+}
+
+/* Of course '$current_module$' isn't the name of the current
+ * module. It'll do if no module is explicitly specified through
+ * (:)/2.
+ */
+impl ClauseConsistency for Term {
+    fn name_and_module(&self) -> Option<(ClauseName, ClauseName)>
+    {
+        match self {
+            Term::Clause(_, ref name, ref terms, _) =>
+                match name.as_str() {
+                    ":-" => {
+                        match terms.len() {
+                            1 => None, // a declaration.
+                            2 => resolved_term_and_module(&terms[0]),
+                            _ => Some((name.owning_module(), clause_name!(":-"))),
+                        }
+                    }
+                    _ => {
+                        resolved_term_and_module(self)
+                    }
+                },
+            Term::Constant(_, Constant::Atom(ref name, _)) => {
+                Some((name.owning_module(), name.clone()))
+            }
+            _ => {
+                None
+            }
+        }
+    }
+
+    fn arity(&self) -> usize {
+        match self {
+            Term::Clause(_, ref name, ref terms, _) =>
+                match name.as_str() {
+                    ":-" => {
+                        match terms.len() {
+                            1 => 0,
+                            2 => resolved_term_arity(&terms[0]),
+                            _ => terms.len(),
+                        }
+                    }
+                    _ => {
+                        resolved_term_arity(self)
+                    }
+                },
+            _ => {
+                0
+            }
+        }
+    }
+}
+
+impl ClauseConsistency for Rule {
+    fn name_and_module(&self) -> Option<(ClauseName, ClauseName)> {
+        Some((self.head.0.owning_module(), self.head.0.clone()))
+    }
+
+    fn arity(&self) -> usize {
+        self.head.1.len()
+    }
+}
+
+impl ClauseConsistency for PredicateClause {
+    fn name_and_module(&self) -> Option<(ClauseName, ClauseName)> {
+        match self {
+            &PredicateClause::Fact(ref term, ..) => {
+                term.name_and_module()
+                    .map(|(_, name)| (name.owning_module(), name))
+            }
+            &PredicateClause::Rule(ref rule, ..) => {
+                rule.name_and_module()
+            }
+        }
+    }
+
+    fn arity(&self) -> usize {
+        match self {
+            &PredicateClause::Fact(ref term, ..) => {
+                term.arity()
+            }
+            &PredicateClause::Rule(ref rule, ..) => {
+                rule.arity()
+            }
+        }
+    }
+}
+
+impl ClauseConsistency for Predicate {
+    fn name_and_module(&self) -> Option<(ClauseName, ClauseName)> {
+        self.0.first().and_then(|clause| clause.name_and_module())
+    }
+
+    fn arity(&self) -> usize {
+        self.0.first().map(|clause| clause.arity()).unwrap_or(0)
+    }
+}
+
+pub type CompiledResult = (Predicate, VecDeque<TopLevel>);
+
+#[derive(Debug, Clone)]
+pub enum PredicateClause {
+    Fact(Term, usize, usize), // Term, line number, column number.
+    Rule(Rule, usize, usize), // Term, line number, column number.
+}
+
+impl PredicateClause {
+    pub fn first_arg(&self) -> Option<&Term> {
+        match self {
+            &PredicateClause::Fact(ref term, ..) => term.first_arg(),
+            &PredicateClause::Rule(ref rule, ..) => rule.head.1.first().map(|bt| bt.as_ref()),
+        }
+    }
+
+    pub fn arity(&self) -> usize {
+        match self {
+            &PredicateClause::Fact(ref term, ..) => {
+                term.arity()
+            }
+            &PredicateClause::Rule(ref rule, ..) => {
+                if rule.head.0.as_str() == ":" && rule.head.1.len() == 2 {
+                    match (rule.head.1)[0].as_ref() {
+                        &Term::Constant(_, Constant::Atom(..)) => {
+                        }
+                        _ => {
+                            return 2;
+                        }
+                    }
+
+                    (rule.head.1)[1].arity()
+                } else {
+                    rule.head.1.len()
+                }
+            }
+        }
+    }
+
+    pub fn name(&self) -> Option<ClauseName> {
+        match self {
+            &PredicateClause::Fact(ref term, ..) => term.name(),
+            &PredicateClause::Rule(ref rule, ..) => Some(rule.head.0.clone()),
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub enum ModuleSource {
+    Library(ClauseName),
+    File(ClauseName),
+}
+
+impl ModuleSource {
+    pub fn as_functor_stub(&self) -> MachineStub {
+        match self {
+            ModuleSource::Library(ref name) => {
+                functor!("library", [clause_name(name.clone())])
+            }
+            ModuleSource::File(ref name) => {
+                functor!(clause_name(name.clone()))
+            }
+        }
+    }
+}
+
+pub type ScopedPredicateKey = (ClauseName, PredicateKey); // module name, predicate indicator.
+
+#[derive(Debug, Clone)]
+pub enum MultiFileIndicator {
+    LocalScoped(ClauseName, usize), // name, arity
+    ModuleScoped(ScopedPredicateKey),
+}
+
+#[derive(Debug, Clone)]
+pub enum Declaration {
+    Dynamic(ClauseName, usize), // name, arity
+    EndOfFile,
+    Hook(CompileTimeHook, PredicateClause, VecDeque<TopLevel>),
+    ModuleInitialization(Vec<QueryTerm>, VecDeque<TopLevel>), // goal
+    Module(ModuleDecl),
+    MultiFile(MultiFileIndicator),
+    NonCountedBacktracking(ClauseName, usize), // name, arity
+    Op(OpDecl),
+    SetPrologFlag(DoubleQuotes),
+    UseModule(ModuleSource),
+    UseQualifiedModule(ModuleSource, Vec<ModuleExport>),
+}
+
+impl Declaration {
+    #[inline]
+    pub fn is_module_decl(&self) -> bool {
+        if let &Declaration::Module(_) = self {
+            true
+        } else {
+            false
+        }
+    }
+
+    #[inline]
+    pub fn is_end_of_file(&self) -> bool {
+        if let &Declaration::EndOfFile = self {
+            true
+        } else {
+            false
+        }
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
+pub struct OpDecl(pub usize, pub Specifier, pub ClauseName);
+
+impl OpDecl {
+    #[inline]
+    pub fn name(&self) -> ClauseName {
+        self.2.clone()
+    }
+
+    #[inline]
+    pub fn remove(&self, op_dir: &mut OpDir) {
+        self.insert_into_op_dir(clause_name!(""), op_dir, 0);
+    }
+
+    #[inline]
+    pub fn fixity(&self) -> Fixity {
+        match self.1 {
+            XFY | XFX | YFX => Fixity::In,
+            XF | YF => Fixity::Post,
+            FX | FY => Fixity::Pre,
+            _ => unreachable!()
+        }
+    }
+
+    pub fn insert_into_op_dir(&self, module: ClauseName, op_dir: &mut OpDir, prec: usize) {
+        let (spec, name) = (self.1, self.2.clone());
+
+        let fixity = self.fixity();
+
+        match op_dir.get(&(name.clone(), fixity)) {
+            Some(cell) => {
+                cell.shared_op_desc().set(prec, spec);
+                return;
+            }
+            None => {}
+        }
+
+        op_dir.insert((name, fixity), OpDirValue::new(spec, prec, module));
+    }
+
+    pub fn submit(
+        &self,
+        module: ClauseName,
+        existing_desc: Option<OpDesc>,
+        op_dir: &mut OpDir,
+    ) -> Result<(), SessionError> {
+        let (prec, spec, name) = (self.0, self.1, self.2.clone());
+
+        if is_infix!(spec) {
+            if let Some(desc) = existing_desc {
+                if desc.post > 0 {
+                    return Err(SessionError::OpIsInfixAndPostFix(name));
+                }
+            }
+        }
+
+        if is_postfix!(spec) {
+            if let Some(desc) = existing_desc {
+                if desc.inf > 0 {
+                    return Err(SessionError::OpIsInfixAndPostFix(name));
+                }
+            }
+        }
+
+        Ok(self.insert_into_op_dir(module, op_dir, prec))
+    }
+}
+
+pub fn fetch_atom_op_spec(
+    name: ClauseName,
+    spec: Option<SharedOpDesc>,
+    op_dir: &OpDir,
+) -> Option<SharedOpDesc> {
+    fetch_op_spec_from_existing(name.clone(), 1, spec.clone(), op_dir)
+        .or_else(|| fetch_op_spec_from_existing(name, 2, spec, op_dir))
+}
+
+pub fn fetch_op_spec_from_existing(
+    name: ClauseName,
+    arity: usize,
+    spec: Option<SharedOpDesc>,
+    op_dir: &OpDir,
+) -> Option<SharedOpDesc> {
+    if let Some(ref op_desc) = &spec {
+        if op_desc.arity() != arity {
+            /* it's possible to extend operator functors with
+             * additional terms. When that happens,
+             * void the op_spec by returning None. */
+            return None;
+        }
+    }
+
+    spec.or_else(|| fetch_op_spec(name, arity, op_dir))
+}
+
+pub fn fetch_op_spec(
+    name: ClauseName,
+    arity: usize,
+    op_dir: &OpDir,
+) -> Option<SharedOpDesc> {
+    match arity {
+        2 => op_dir
+            .get(&(name, Fixity::In))
+            .and_then(|OpDirValue(spec, _)| {
+                if spec.prec() > 0 {
+                    Some(spec.clone())
+                } else {
+                    None
+                }
+            }),
+        1 => {
+            if let Some(OpDirValue(spec, _)) = op_dir.get(&(name.clone(), Fixity::Pre)) {
+                if spec.prec() > 0 {
+                    return Some(spec.clone());
+                }
+            }
+
+            op_dir
+                .get(&(name, Fixity::Post))
+                .and_then(|OpDirValue(spec, _)| {
+                    if spec.prec() > 0 {
+                        Some(spec.clone())
+                    } else {
+                        None
+                    }
+                })
+        }
+        _ => {
+            None
+        }
+    }
+}
+
+pub type ModuleDir = IndexMap<ClauseName, Module>;
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum ModuleExport {
+    OpDecl(OpDecl),
+    PredicateKey(PredicateKey),
+}
+
+#[derive(Debug, Clone)]
+pub struct ModuleDecl {
+    pub name: ClauseName,
+    pub exports: Vec<ModuleExport>,
+}
+
+#[derive(Debug)]
+pub struct Module {
+    pub atom_tbl: TabledData<Atom>,
+    pub module_decl: ModuleDecl,
+    pub code_dir: CodeDir,
+    pub op_dir: OpDir,
+    pub term_dir: TermDir, // this contains multifile predicates.
+    pub term_expansions: (Predicate, VecDeque<TopLevel>),
+    pub goal_expansions: (Predicate, VecDeque<TopLevel>),
+    pub user_term_expansions: (Predicate, VecDeque<TopLevel>), // term expansions inherited from the user scope.
+    pub user_goal_expansions: (Predicate, VecDeque<TopLevel>), // same for goal_expansions.
+    pub local_term_expansions: (Predicate, VecDeque<TopLevel>), // expansions local to the module.
+    pub local_goal_expansions: (Predicate, VecDeque<TopLevel>),
+    pub inserted_expansions: bool, // has the module been successfully inserted into toplevel??
+    pub is_impromptu_module: bool,
+    pub listing_src: ListingSource,
+ }
+
+#[derive(Debug, Clone)]
+pub enum Number {
+    Float(OrderedFloat<f64>),
+    Integer(Rc<Integer>),
+    Rational(Rc<Rational>),
+    Fixnum(isize),
+}
+
+impl From<Integer> for Number {
+    #[inline]
+    fn from(n: Integer) -> Self {
+        Number::Integer(Rc::new(n))
+    }
+}
+
+impl From<Rational> for Number {
+    #[inline]
+    fn from(n: Rational) -> Self {
+        Number::Rational(Rc::new(n))
+    }
+}
+
+impl From<isize> for Number {
+    #[inline]
+    fn from(n: isize) -> Self {
+        Number::Fixnum(n)
+    }
+}
+
+impl Default for Number {
+    fn default() -> Self {
+        Number::Float(OrderedFloat(0f64))
+    }
+}
+
+impl Into<Constant> for Number {
+    #[inline]
+    fn into(self) -> Constant {
+        match self {
+            Number::Fixnum(n) => Constant::Fixnum(n),
+            Number::Integer(n) => Constant::Integer(n),
+            Number::Float(f) => Constant::Float(f),
+            Number::Rational(r) => Constant::Rational(r),
+        }
+    }
+}
+
+impl Into<HeapCellValue> for Number {
+    #[inline]
+    fn into(self) -> HeapCellValue {
+        match self {
+            Number::Fixnum(n) => HeapCellValue::Addr(Addr::Fixnum(n)),
+            Number::Integer(n) => HeapCellValue::Integer(n),
+            Number::Float(f) => HeapCellValue::Addr(Addr::Float(f)),
+            Number::Rational(r) => HeapCellValue::Rational(r),
+        }
+    }
+}
+
+
+impl Number {
+    #[inline]
+    pub fn is_positive(&self) -> bool {
+        match self {
+            &Number::Fixnum(n) => n > 0,
+            &Number::Integer(ref n) => &**n > &0,
+            &Number::Float(OrderedFloat(f)) => f.is_sign_positive(),
+            &Number::Rational(ref r) => &**r > &0,
+        }
+    }
+
+    #[inline]
+    pub fn is_negative(&self) -> bool {
+        match self {
+            &Number::Fixnum(n) => n < 0,
+            &Number::Integer(ref n) => &**n < &0,
+            &Number::Float(OrderedFloat(f)) => f.is_sign_negative(),
+            &Number::Rational(ref r) => &**r < &0,
+        }
+    }
+
+    #[inline]
+    pub fn is_zero(&self) -> bool {
+        match self {
+            &Number::Fixnum(n) => n == 0,
+            &Number::Integer(ref n) => &**n == &0,
+            &Number::Float(f) => f == OrderedFloat(0f64),
+            &Number::Rational(ref r) => &**r == &0,
+        }
+    }
+
+    #[inline]
+    pub fn abs(self) -> Self {
+        match self {
+            Number::Fixnum(n) =>
+                if let Some(n) = n.checked_abs() {
+                    Number::from(n)
+                } else {
+                    Number::from(Integer::from(n).abs())
+                }
+            Number::Integer(n) => Number::from(Integer::from(n.abs_ref())),
+            Number::Float(f) => Number::Float(OrderedFloat(f.abs())),
+            Number::Rational(r) => Number::from(Rational::from(r.abs_ref())),
+        }
+    }
+}

src/heap_iter.rs

@@ -0,0 +1,342 @@
+use crate::machine::machine_indices::*;
+use crate::machine::machine_state::*;
+
+use crate::indexmap::IndexSet;
+
+use std::cmp::Ordering;
+use std::ops::Deref;
+use std::vec::Vec;
+
+#[derive(Debug)]
+pub struct HCPreOrderIterator<'a> {
+    pub machine_st: &'a MachineState,
+    pub state_stack: Vec<Addr>,
+}
+
+impl<'a> HCPreOrderIterator<'a> {
+    pub fn new(machine_st: &'a MachineState, a: Addr) -> Self {
+        HCPreOrderIterator {
+            machine_st,
+            state_stack: vec![a],
+        }
+    }
+
+    #[inline]
+    pub fn machine_st(&self) -> &MachineState {
+        &self.machine_st
+    }
+
+    fn follow_heap(&mut self, h: usize) -> Addr {
+        match &self.machine_st.heap[h] {
+            &HeapCellValue::NamedStr(arity, _, _) => {
+                for idx in (1 .. arity + 1).rev() {
+                    self.state_stack.push(Addr::HeapCell(h + idx));
+                }
+
+                Addr::Str(h)
+            }
+            &HeapCellValue::Addr(a) => {
+                self.follow(a)
+            }
+            HeapCellValue::PartialString(..) => {
+                self.follow(Addr::PStrLocation(h, 0))
+            }
+            HeapCellValue::Atom(..) | HeapCellValue::DBRef(_)
+          | HeapCellValue::Integer(_) | HeapCellValue::Rational(_) => {
+                Addr::Con(h)
+            }
+            HeapCellValue::Stream(_) => {
+                Addr::Stream(h)
+            }
+            &HeapCellValue::TcpListener(_) => {
+                Addr::TcpListener(h)
+            }
+        }
+    }
+
+    // called under the assumption that the location at r is about to
+    // be visited, and so any follow up states need to be added to
+    // state_stack. returns the dereferenced Addr from Ref.
+    fn follow(&mut self, addr: Addr) -> Addr {
+        let da = self.machine_st.store(self.machine_st.deref(addr));
+
+        match da {
+            Addr::Lis(a) => {
+                self.state_stack.push(Addr::HeapCell(a + 1));
+                self.state_stack.push(Addr::HeapCell(a));
+
+                da
+            }
+            Addr::PStrLocation(h, n) => {
+                if let &HeapCellValue::PartialString(ref pstr, has_tail) = &self.machine_st.heap[h] {
+                    if let Some(c) = pstr.range_from(n ..).next() {
+                        if !pstr.at_end(n + c.len_utf8()) {
+                            self.state_stack.push(Addr::PStrLocation(h, n + c.len_utf8()));
+                        } else if has_tail {
+                            self.state_stack.push(Addr::HeapCell(h + 1));
+                        } else {
+                            self.state_stack.push(Addr::EmptyList);
+                        }
+
+                        self.state_stack.push(Addr::Char(c));
+                    } else if has_tail {
+                        return self.follow(Addr::HeapCell(h + 1));
+                    }
+                } else {
+                    unreachable!()
+                }
+
+                Addr::PStrLocation(h, n)
+            }
+            Addr::Str(s) => {
+                self.follow_heap(s) // record terms of structure.
+            }
+            Addr::Con(h) => {
+                if let &HeapCellValue::PartialString(ref pstr, has_tail) = &self.machine_st.heap[h] {
+                    if let Some(c) = pstr.range_from(0 ..).next() {
+                        self.state_stack.push(Addr::PStrLocation(h, c.len_utf8()));
+                        self.state_stack.push(Addr::Char(c));
+
+                        Addr::PStrLocation(h, 0)
+                    } else if has_tail {
+                        self.follow(Addr::HeapCell(h + 1))
+                    } else {
+                        Addr::EmptyList
+                    }
+                } else {
+                    Addr::Con(h)
+                }
+            }
+            da => {
+                da
+            }
+        }
+    }
+}
+
+impl<'a> Iterator for HCPreOrderIterator<'a> {
+    type Item = Addr;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.state_stack.pop().map(|a| self.follow(a))
+    }
+}
+
+pub trait MutStackHCIterator<'b> where Self: Iterator
+{
+    type MutStack;
+
+    fn stack(&'b mut self) -> Self::MutStack;
+}
+
+#[derive(Debug)]
+pub struct HCPostOrderIterator<'a> {
+    base_iter: HCPreOrderIterator<'a>,
+    parent_stack: Vec<(usize, Addr)>, // number of children, parent node.
+}
+
+impl<'a> Deref for HCPostOrderIterator<'a> {
+    type Target = HCPreOrderIterator<'a>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.base_iter
+    }
+}
+
+impl<'a> HCPostOrderIterator<'a> {
+    pub fn new(base_iter: HCPreOrderIterator<'a>) -> Self {
+        HCPostOrderIterator {
+            base_iter,
+            parent_stack: vec![],
+        }
+    }
+}
+
+impl<'a> Iterator for HCPostOrderIterator<'a> {
+    type Item = Addr;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        loop {
+            if let Some((child_count, node)) = self.parent_stack.pop() {
+                if child_count == 0 {
+                    return Some(node);
+                }
+
+                self.parent_stack.push((child_count - 1, node));
+            }
+
+            if let Some(item) = self.base_iter.next() {
+                match self.base_iter.machine_st.heap.index_addr(&item).as_ref() {
+                    &HeapCellValue::NamedStr(arity, ..) => {
+                        self.parent_stack.push((arity, item));
+                    }
+                    &HeapCellValue::Addr(Addr::Lis(a)) => {
+                        self.parent_stack.push((2, Addr::Lis(a)));
+                    }
+                    &HeapCellValue::Addr(Addr::PStrLocation(h, n)) => {
+                        match &self.machine_st.heap[h] {
+                            &HeapCellValue::PartialString(ref pstr, _) => {
+                                let c = pstr.range_from(n ..).next().unwrap();
+                                let next_n = n + c.len_utf8();
+
+                                if !pstr.at_end(next_n) {
+                                    self.parent_stack.push((2, Addr::PStrLocation(h, next_n)));
+                                }
+                            }
+                            _ => {
+                                unreachable!()
+                            }
+                        }
+                    }
+                    _ => {
+                        return Some(item);
+                    }
+                }
+            } else {
+                return None;
+            }
+        }
+    }
+}
+
+impl MachineState {
+    pub fn pre_order_iter<'a>(&'a self, a: Addr) -> HCPreOrderIterator<'a> {
+        HCPreOrderIterator::new(self, a)
+    }
+
+    pub fn post_order_iter<'a>(&'a self, a: Addr) -> HCPostOrderIterator<'a> {
+        HCPostOrderIterator::new(HCPreOrderIterator::new(self, a))
+    }
+
+    pub fn acyclic_pre_order_iter<'a>(&'a self, a: Addr,) -> HCAcyclicIterator<'a> {
+        HCAcyclicIterator::new(HCPreOrderIterator::new(self, a))
+    }
+
+    pub fn zipped_acyclic_pre_order_iter<'a>(
+        &'a self,
+        a1: Addr,
+        a2: Addr,
+    ) -> HCZippedAcyclicIterator<'a> {
+        HCZippedAcyclicIterator::new(
+            HCPreOrderIterator::new(self, a1),
+            HCPreOrderIterator::new(self, a2),
+        )
+    }
+}
+
+impl<'b, 'a: 'b> MutStackHCIterator<'b> for HCPreOrderIterator<'a> {
+    type MutStack = &'b mut Vec<Addr>;
+
+    fn stack(&'b mut self) -> Self::MutStack {
+        &mut self.state_stack
+    }
+}
+
+#[derive(Debug)]
+pub struct HCAcyclicIterator<'a> {
+    iter: HCPreOrderIterator<'a>,
+    seen: IndexSet<Addr>,
+}
+
+impl<'a> HCAcyclicIterator<'a> {
+    pub fn new(iter: HCPreOrderIterator<'a>) -> Self {
+        HCAcyclicIterator {
+            iter,
+            seen: IndexSet::new(),
+        }
+    }
+}
+
+impl<'a> Deref for HCAcyclicIterator<'a> {
+    type Target = HCPreOrderIterator<'a>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.iter
+    }
+}
+
+impl<'b, 'a: 'b> MutStackHCIterator<'b> for HCAcyclicIterator<'a> {
+    type MutStack = &'b mut Vec<Addr>;
+
+    fn stack(&'b mut self) -> Self::MutStack {
+        self.iter.stack()
+    }
+}
+
+impl<'a> Iterator for HCAcyclicIterator<'a>
+{
+    type Item = Addr;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        while let Some(addr) = self.iter.stack().pop() {
+            if !self.seen.contains(&addr) {
+                self.iter.stack().push(addr.clone());
+                self.seen.insert(addr);
+
+                break;
+            }
+        }
+
+        self.iter.next()
+    }
+}
+
+#[derive(Debug)]
+pub struct HCZippedAcyclicIterator<'a> {
+    i1: HCPreOrderIterator<'a>,
+    i2: HCPreOrderIterator<'a>,
+    seen: IndexSet<(Addr, Addr)>,
+    pub first_to_expire: Ordering,
+}
+
+impl<'b, 'a: 'b> MutStackHCIterator<'b> for HCZippedAcyclicIterator<'a> {
+    type MutStack = (&'b mut Vec<Addr>, &'b mut Vec<Addr>);
+
+    fn stack(&'b mut self) -> Self::MutStack {
+        (self.i1.stack(), self.i2.stack())
+    }
+}
+
+impl<'a> HCZippedAcyclicIterator<'a> {
+    pub fn new(i1: HCPreOrderIterator<'a>, i2: HCPreOrderIterator<'a>) -> Self {
+        HCZippedAcyclicIterator {
+            i1,
+            i2,
+            seen: IndexSet::new(),
+            first_to_expire: Ordering::Equal,
+        }
+    }
+}
+
+impl<'a> Iterator for HCZippedAcyclicIterator<'a>
+{
+    type Item = (Addr, Addr);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        while let (Some(a1), Some(a2)) = (self.i1.stack().pop(), self.i2.stack().pop()) {
+            if !self.seen.contains(&(a1.clone(), a2.clone())) {
+                self.i1.stack().push(a1.clone());
+                self.i2.stack().push(a2.clone());
+
+                self.seen.insert((a1, a2));
+
+                break;
+            }
+        }
+
+        match (self.i1.next(), self.i2.next()) {
+            (Some(v1), Some(v2)) => Some((v1, v2)),
+            (Some(_), None) => {
+                self.first_to_expire = Ordering::Greater;
+                None
+            }
+            (None, Some(_)) => {
+                self.first_to_expire = Ordering::Less;
+                None
+            }
+            _ => {
+                None
+            }
+        }
+    }
+}

src/indexing.rs

@@ -1,30 +1,35 @@
-use prolog_parser::ast::*;
+use crate::prolog_parser::ast::*;
+use crate::prolog_parser::tabled_rc::*;
 
-use crate::prolog::instructions::*;
+use crate::instructions::*;
+use crate::rug::Integer;
 
-use indexmap::IndexMap;
+use crate::indexmap::IndexMap;
 
 use std::collections::VecDeque;
+use std::convert::TryFrom;
 use std::hash::Hash;
+use std::rc::Rc;
 
-#[derive(Clone, Copy)]
+#[derive(Debug, Clone, Copy)]
 enum IntIndex {
     External(usize),
     Fail,
     Internal(usize),
 }
 
+#[derive(Debug)]
 pub struct CodeOffsets {
-    flags: MachineFlags,
+    atom_tbl: TabledData<Atom>,
     pub constants: IndexMap<Constant, ThirdLevelIndex>,
     pub lists: ThirdLevelIndex,
     pub structures: IndexMap<(ClauseName, usize), ThirdLevelIndex>,
 }
 
 impl CodeOffsets {
-    pub fn new(flags: MachineFlags) -> Self {
+    pub fn new() -> Self {
         CodeOffsets {
-            flags,
+            atom_tbl: TabledData::new(Rc::new("_index".to_string())),
             constants: IndexMap::new(),
             lists: Vec::new(),
             structures: IndexMap::new(),
@@ -50,6 +55,94 @@ impl CodeOffsets {
         }
     }
 
+    fn intercept_overlapping_constant(&mut self, constant: &Constant, index: usize) {
+        match constant {
+            &Constant::Atom(ref name, ref op) if name.is_char() => {
+                let c = name.as_str().chars().next().unwrap();
+                let code = self.constants
+                    .entry(Constant::Char(c))
+                    .or_insert(vec![]);
+
+                code.push(Self::add_index(code.is_empty(), index));
+
+                if op.is_some() {
+                    let code = self.constants
+                        .entry(Constant::Atom(name.clone(), None))
+                        .or_insert(vec![]);
+
+                    code.push(Self::add_index(false, index));
+                }
+            }
+            &Constant::Atom(ref name, Some(_)) => {
+                let code = self.constants
+                    .entry(Constant::Atom(name.clone(), None))
+                    .or_insert(vec![]);
+
+                code.push(Self::add_index(code.is_empty(), index));
+            }
+            &Constant::Char(c) => {
+                let atom = clause_name!(c.to_string(), self.atom_tbl.clone());
+
+                let code = self.constants
+                    .entry(Constant::Atom(atom, None))
+                    .or_insert(vec![]);
+
+                code.push(Self::add_index(code.is_empty(), index));
+            }
+            &Constant::Fixnum(n) => {
+                let code = self.constants
+                    .entry(Constant::Integer(Rc::new(Integer::from(n))))
+                    .or_insert(vec![]);
+
+                code.push(Self::add_index(code.is_empty(), index));
+
+                if n >= 0 {
+                    if let Ok(n) = usize::try_from(n) {
+                        let code = self.constants
+                            .entry(Constant::Usize(n))
+                            .or_insert(vec![]);
+
+                        code.push(Self::add_index(code.is_empty(), index));
+                    }
+                }
+            }
+            &Constant::Integer(ref n) => {
+                if let Some(n) = n.to_isize() {
+                    let code = self.constants
+                        .entry(Constant::Fixnum(n))
+                        .or_insert(vec![]);
+
+                    code.push(Self::add_index(code.is_empty(), index));
+                }
+
+                if let Some(n) = n.to_usize() {
+                    let code = self.constants
+                        .entry(Constant::Usize(n))
+                        .or_insert(vec![]);
+
+                    code.push(Self::add_index(code.is_empty(), index));
+                }
+            }
+            &Constant::Usize(n) => {
+                let code = self.constants
+                    .entry(Constant::Integer(Rc::new(Integer::from(n))))
+                    .or_insert(vec![]);
+
+                code.push(Self::add_index(code.is_empty(), index));
+
+                if let Ok(n) = isize::try_from(n) {
+                    let code = self.constants
+                        .entry(Constant::Fixnum(n))
+                        .or_insert(vec![]);
+
+                    code.push(Self::add_index(code.is_empty(), index));
+                }
+            }
+            _ => {
+            }
+        }
+    }
+
     pub fn index_term(&mut self, first_arg: &Term, index: usize) {
         match first_arg {
             &Term::Clause(_, ref name, ref terms, _) => {
@@ -61,30 +154,22 @@ impl CodeOffsets {
                 let is_initial_index = code.is_empty();
                 code.push(Self::add_index(is_initial_index, index));
             }
-            &Term::Cons(..) => {
-                let is_initial_index = self.lists.is_empty();
-                self.lists.push(Self::add_index(is_initial_index, index));
-            }
-            &Term::Constant(_, Constant::String(ref s))
-                if !self.flags.double_quotes.is_atom() && !s.is_empty() =>
-            {
-                // strings are lists in this case.
-                let is_initial_index = self.lists.is_empty();
-                self.lists.push(Self::add_index(is_initial_index, index));
-            }
-            &Term::Constant(_, Constant::String(ref s))
-                if !self.flags.double_quotes.is_atom() && s.is_expandable() =>
-            {
+            &Term::Cons(..) | &Term::Constant(_, Constant::String(_)) => {
                 let is_initial_index = self.lists.is_empty();
                 self.lists.push(Self::add_index(is_initial_index, index));
             }
             &Term::Constant(_, ref constant) => {
-                let code = self.constants.entry(constant.clone()).or_insert(Vec::new());
+                self.intercept_overlapping_constant(constant, index);
+
+                let code = self.constants
+                    .entry(constant.clone())
+                    .or_insert(vec![]);
 
                 let is_initial_index = code.is_empty();
                 code.push(Self::add_index(is_initial_index, index));
             }
-            _ => {}
+            _ => {
+            }
         };
     }
 
@@ -232,12 +317,11 @@ impl CodeOffsets {
     fn switch_on_lst_offset_from(
         lst_loc: IntIndex,
         prelude_len: usize,
-        lst_offset: usize,
     ) -> usize {
         match lst_loc {
             IntIndex::External(o) => o + prelude_len + 1,
             IntIndex::Fail => 0,
-            IntIndex::Internal(_) => prelude_len - lst_offset + 1,
+            IntIndex::Internal(_) => 1, // this internal is always 0.
         }
     }
 
@@ -250,8 +334,6 @@ impl CodeOffsets {
         let mut prelude = VecDeque::new();
 
         let lst_loc = Self::switch_on_list(self.lists, &mut prelude);
-        let lst_offset = prelude.len();
-
         let str_loc = Self::switch_on_structure(self.structures, &mut prelude);
         let con_loc = Self::switch_on_constant(self.constants, &mut prelude);
 
@@ -259,18 +341,19 @@ impl CodeOffsets {
 
         for (index, line) in prelude.iter_mut().enumerate() {
             match line {
-                &mut Line::IndexedChoice(IndexedChoiceInstruction::Try(ref mut i))
-                | &mut Line::IndexedChoice(IndexedChoiceInstruction::Retry(ref mut i))
-                | &mut Line::IndexedChoice(IndexedChoiceInstruction::Trust(ref mut i)) => {
-                    *i += prelude_length - index
+                &mut Line::IndexedChoice(IndexedChoiceInstruction::Try(ref mut i)) |
+                &mut Line::IndexedChoice(IndexedChoiceInstruction::Retry(ref mut i)) |
+                &mut Line::IndexedChoice(IndexedChoiceInstruction::Trust(ref mut i)) => {
+                    *i += prelude_length - index;
+                }
+                _ => {
                 }
-                _ => {}
             }
         }
 
         let str_loc = Self::switch_on_str_offset_from(str_loc, prelude.len(), con_loc);
         let con_loc = Self::switch_on_con_offset_from(con_loc, prelude.len());
-        let lst_loc = Self::switch_on_lst_offset_from(lst_loc, prelude.len(), lst_offset);
+        let lst_loc = Self::switch_on_lst_offset_from(lst_loc, prelude.len());
 
         let switch_instr =
             IndexingInstruction::SwitchOnTerm(prelude.len() + 1, con_loc, lst_loc, str_loc);

src/instructions.rs

@@ -1,29 +1,30 @@
-use prolog_parser::ast::*;
+use crate::prolog_parser::ast::*;
 
-use crate::prolog::clause_types::*;
-use crate::prolog::forms::*;
-use crate::prolog::machine::machine_errors::MachineStub;
-use crate::prolog::machine::machine_indices::*;
+use crate::clause_types::*;
+use crate::forms::*;
+use crate::machine::heap::*;
+use crate::machine::machine_errors::MachineStub;
+use crate::machine::machine_indices::*;
+use crate::rug::Integer;
 
-use crate::prolog::rug::Integer;
-
-use indexmap::IndexMap;
+use crate::indexmap::IndexMap;
 
 use std::collections::VecDeque;
+use std::rc::Rc;
 
 fn reg_type_into_functor(r: RegType) -> MachineStub {
     match r {
-        RegType::Temp(r) => functor!("x", 1, [heap_integer!(Integer::from(r))]),
-        RegType::Perm(r) => functor!("y", 1, [heap_integer!(Integer::from(r))]),
+        RegType::Temp(r) => functor!("x", [integer(r)]),
+        RegType::Perm(r) => functor!("y", [integer(r)]),
     }
 }
 
 impl Level {
     fn into_functor(self) -> MachineStub {
         match self {
-            Level::Root => functor!("level", 1, [heap_atom!("root")]),
-            Level::Shallow => functor!("level", 1, [heap_atom!("shallow")]),
-            Level::Deep => functor!("level", 1, [heap_atom!("deep")]),
+            Level::Root => functor!("level", [atom("root")]),
+            Level::Shallow => functor!("level", [atom("shallow")]),
+            Level::Deep => functor!("level", [atom("deep")]),
         }
     }
 }
@@ -31,15 +32,20 @@ impl Level {
 impl ArithmeticTerm {
     fn into_functor(&self) -> MachineStub {
         match self {
-            &ArithmeticTerm::Reg(r) => reg_type_into_functor(r),
-            &ArithmeticTerm::Interm(i) => {
-                functor!("intermediate", 1, [heap_integer!(Integer::from(i))])
+            &ArithmeticTerm::Reg(r) => {
+                reg_type_into_functor(r)
+            }
+            &ArithmeticTerm::Interm(i) => {
+                functor!("intermediate", [integer(i)])
+            }
+            &ArithmeticTerm::Number(ref n) => {
+                vec![n.clone().into()]
             }
-            &ArithmeticTerm::Number(ref n) => vec![heap_con!(n.clone().to_constant())],
         }
     }
 }
 
+#[derive(Debug)]
 pub enum ChoiceInstruction {
     DefaultRetryMeElse(usize),
     DefaultTrustMe,
@@ -52,22 +58,25 @@ impl ChoiceInstruction {
     pub fn to_functor(&self) -> MachineStub {
         match self {
             &ChoiceInstruction::TryMeElse(offset) => {
-                functor!("try_me_else", 1, [heap_integer!(Integer::from(offset))])
+                functor!("try_me_else", [integer(offset)])
             }
             &ChoiceInstruction::RetryMeElse(offset) => {
-                functor!("retry_me_else", 1, [heap_integer!(Integer::from(offset))])
+                functor!("retry_me_else", [integer(offset)])
+            }
+            &ChoiceInstruction::TrustMe => {
+                functor!("trust_me")
+            }
+            &ChoiceInstruction::DefaultRetryMeElse(offset) => {
+                functor!("default_retry_me_else", [integer(offset)])
+            }
+            &ChoiceInstruction::DefaultTrustMe => {
+                functor!("default_trust_me")
             }
-            &ChoiceInstruction::TrustMe => vec![heap_atom!("trust_me")],
-            &ChoiceInstruction::DefaultRetryMeElse(offset) => functor!(
-                "default_retry_me_else",
-                1,
-                [heap_integer!(Integer::from(offset))]
-            ),
-            &ChoiceInstruction::DefaultTrustMe => vec![heap_atom!("default_trust_me")],
         }
     }
 }
 
+#[derive(Debug)]
 pub enum CutInstruction {
     Cut(RegType),
     GetLevel(RegType),
@@ -79,25 +88,25 @@ impl CutInstruction {
     pub fn to_functor(&self, h: usize) -> MachineStub {
         match self {
             &CutInstruction::Cut(r) => {
-                let mut stub = functor!("cut", 1, [heap_str!(h + 2)]);
-                stub.append(&mut reg_type_into_functor(r));
-                stub
+                let rt_stub = reg_type_into_functor(r);
+                functor!("cut", [aux(h, 0)], [rt_stub])
             }
             &CutInstruction::GetLevel(r) => {
-                let mut stub = functor!("get_level", 1, [heap_str!(h + 2)]);
-                stub.append(&mut reg_type_into_functor(r));
-                stub
+                let rt_stub = reg_type_into_functor(r);
+                functor!("get_level", [aux(h, 0)], [rt_stub])
             }
             &CutInstruction::GetLevelAndUnify(r) => {
-                let mut stub = functor!("get_level_and_unify", 1, [heap_str!(h + 2)]);
-                stub.append(&mut reg_type_into_functor(r));
-                stub
+                let rt_stub = reg_type_into_functor(r);
+                functor!("get_level_and_unify", [aux(h, 0)], [rt_stub])
+            }
+            &CutInstruction::NeckCut => {
+                functor!("neck_cut")
             }
-            &CutInstruction::NeckCut => vec![heap_atom!("neck_cut")],
         }
     }
 }
 
+#[derive(Debug)]
 pub enum IndexedChoiceInstruction {
     Retry(usize),
     Trust(usize),
@@ -122,18 +131,19 @@ impl IndexedChoiceInstruction {
     pub fn to_functor(&self) -> MachineStub {
         match self {
             &IndexedChoiceInstruction::Try(offset) => {
-                functor!("try", 1, [heap_integer!(Integer::from(offset))])
+                functor!("try", [integer(offset)])
             }
             &IndexedChoiceInstruction::Trust(offset) => {
-                functor!("trust", 1, [heap_integer!(Integer::from(offset))])
+                functor!("trust", [integer(offset)])
             }
             &IndexedChoiceInstruction::Retry(offset) => {
-                functor!("retry", 1, [heap_integer!(Integer::from(offset))])
+                functor!("retry", [integer(offset)])
             }
         }
     }
 }
 
+#[derive(Debug)]
 pub enum Line {
     Arithmetic(ArithmeticInstruction),
     Choice(ChoiceInstruction),
@@ -169,7 +179,7 @@ impl Line {
     }
 }
 
-#[derive(Clone)]
+#[derive(Debug, Clone)]
 pub enum ArithmeticInstruction {
     Add(ArithmeticTerm, ArithmeticTerm, usize),
     Sub(ArithmeticTerm, ArithmeticTerm, usize),
@@ -189,6 +199,8 @@ pub enum ArithmeticInstruction {
     Or(ArithmeticTerm, ArithmeticTerm, usize),
     Mod(ArithmeticTerm, ArithmeticTerm, usize),
     Rem(ArithmeticTerm, ArithmeticTerm, usize),
+    Gcd(ArithmeticTerm, ArithmeticTerm, usize),
+    Sign(ArithmeticTerm, usize),
     Cos(ArithmeticTerm, usize),
     Sin(ArithmeticTerm, usize),
     Tan(ArithmeticTerm, usize),
@@ -218,14 +230,11 @@ fn arith_instr_unary_functor(
 ) -> MachineStub {
     let at_stub = at.into_functor();
 
-    let mut stub = functor!(
+    functor!(
         name,
-        2,
-        [heap_cell!(h + 4), heap_integer!(Integer::from(t))]
-    );
-
-    stub.extend(at_stub.into_iter());
-    stub
+        [aux(h, 0), integer(t)],
+        [at_stub]
+    )
 }
 
 fn arith_instr_bin_functor(
@@ -238,20 +247,11 @@ fn arith_instr_bin_functor(
     let at_1_stub = at_1.into_functor();
     let at_2_stub = at_2.into_functor();
 
-    let mut stub = functor!(
+    functor!(
         name,
-        3,
-        [
-            heap_cell!(h + 4),
-            heap_cell!(h + 4 + at_1_stub.len()),
-            heap_integer!(Integer::from(t))
-        ]
-    );
-
-    stub.extend(at_1_stub.into_iter());
-    stub.extend(at_2_stub.into_iter());
-
-    stub
+        [aux(h, 0), aux(h, 1), integer(t)],
+        [at_1_stub, at_2_stub]
+    )
 }
 
 impl ArithmeticInstruction {
@@ -314,16 +314,42 @@ impl ArithmeticInstruction {
             &ArithmeticInstruction::ATan2(ref at_1, ref at_2, t) => {
                 arith_instr_bin_functor(h, "rem", at_1, at_2, t)
             }
-            &ArithmeticInstruction::Cos(ref at, t) => arith_instr_unary_functor(h, "cos", at, t),
-            &ArithmeticInstruction::Sin(ref at, t) => arith_instr_unary_functor(h, "sin", at, t),
-            &ArithmeticInstruction::Tan(ref at, t) => arith_instr_unary_functor(h, "tan", at, t),
-            &ArithmeticInstruction::Log(ref at, t) => arith_instr_unary_functor(h, "log", at, t),
-            &ArithmeticInstruction::Exp(ref at, t) => arith_instr_unary_functor(h, "exp", at, t),
-            &ArithmeticInstruction::ACos(ref at, t) => arith_instr_unary_functor(h, "acos", at, t),
-            &ArithmeticInstruction::ASin(ref at, t) => arith_instr_unary_functor(h, "asin", at, t),
-            &ArithmeticInstruction::ATan(ref at, t) => arith_instr_unary_functor(h, "atan", at, t),
-            &ArithmeticInstruction::Sqrt(ref at, t) => arith_instr_unary_functor(h, "sqrt", at, t),
-            &ArithmeticInstruction::Abs(ref at, t) => arith_instr_unary_functor(h, "abs", at, t),
+            &ArithmeticInstruction::Gcd(ref at_1, ref at_2, t) => {
+                arith_instr_bin_functor(h, "gcd", at_1, at_2, t)
+            }
+            &ArithmeticInstruction::Sign(ref at, t) => {
+                arith_instr_unary_functor(h, "sign", at, t)
+            }
+            &ArithmeticInstruction::Cos(ref at, t)  => {
+                arith_instr_unary_functor(h, "cos", at, t)
+            }
+            &ArithmeticInstruction::Sin(ref at, t)  => {
+                arith_instr_unary_functor(h, "sin", at, t)
+            }
+            &ArithmeticInstruction::Tan(ref at, t)  => {
+                arith_instr_unary_functor(h, "tan", at, t)
+            }
+            &ArithmeticInstruction::Log(ref at, t)  => {
+                arith_instr_unary_functor(h, "log", at, t)
+            }
+            &ArithmeticInstruction::Exp(ref at, t)  => {
+                arith_instr_unary_functor(h, "exp", at, t)
+            }
+            &ArithmeticInstruction::ACos(ref at, t) => {
+                arith_instr_unary_functor(h, "acos", at, t)
+            }
+            &ArithmeticInstruction::ASin(ref at, t) => {
+                arith_instr_unary_functor(h, "asin", at, t)
+            }
+            &ArithmeticInstruction::ATan(ref at, t) => {
+                arith_instr_unary_functor(h, "atan", at, t)
+            }
+            &ArithmeticInstruction::Sqrt(ref at, t) => {
+                arith_instr_unary_functor(h, "sqrt", at, t)
+            }
+            &ArithmeticInstruction::Abs(ref at, t) => {
+                arith_instr_unary_functor(h, "abs", at, t)
+            }
             &ArithmeticInstruction::Float(ref at, t) => {
                 arith_instr_unary_functor(h, "float", at, t)
             }
@@ -339,8 +365,12 @@ impl ArithmeticInstruction {
             &ArithmeticInstruction::Floor(ref at, t) => {
                 arith_instr_unary_functor(h, "floor", at, t)
             }
-            &ArithmeticInstruction::Neg(ref at, t) => arith_instr_unary_functor(h, "-", at, t),
-            &ArithmeticInstruction::Plus(ref at, t) => arith_instr_unary_functor(h, "+", at, t),
+            &ArithmeticInstruction::Neg(ref at, t) => {
+                arith_instr_unary_functor(h, "-", at, t)
+            }
+            &ArithmeticInstruction::Plus(ref at, t) => {
+                arith_instr_unary_functor(h, "+", at, t)
+            }
             &ArithmeticInstruction::BitwiseComplement(ref at, t) => {
                 arith_instr_unary_functor(h, "\\", at, t)
             }
@@ -348,6 +378,7 @@ impl ArithmeticInstruction {
     }
 }
 
+#[derive(Debug)]
 pub enum ControlInstruction {
     Allocate(usize), // num_frames.
     // name, arity, perm_vars after threshold, last call, use default call policy.
@@ -358,44 +389,42 @@ pub enum ControlInstruction {
 }
 
 impl ControlInstruction {
-    pub fn is_jump_instr(&self) -> bool {
+    pub fn perm_vars(&self) -> Option<usize> {
         match self {
-            &ControlInstruction::CallClause(..) => true,
-            &ControlInstruction::JmpBy(..) => true,
-            _ => false,
+            ControlInstruction::CallClause(_, _, num_cells, ..) =>
+                Some(*num_cells),
+            ControlInstruction::JmpBy(_, _, num_cells, ..) =>
+                Some(*num_cells),
+            _ =>
+                None
         }
     }
 
     pub fn to_functor(&self) -> MachineStub {
         match self {
             &ControlInstruction::Allocate(num_frames) => {
-                functor!("allocate", 1, [heap_integer!(Integer::from(num_frames))])
+                functor!("allocate", [integer(num_frames)])
+            }
+            &ControlInstruction::CallClause(ref ct, arity, _, false, _) => {
+                functor!("call", [clause_name(ct.name()), integer(arity)])
+            }
+            &ControlInstruction::CallClause(ref ct, arity, _, true, _) => {
+                functor!("execute", [clause_name(ct.name()), integer(arity)])
+            }
+            &ControlInstruction::Deallocate => {
+                functor!("deallocate")
             }
-            &ControlInstruction::CallClause(ref ct, arity, _, false, _) => functor!(
-                "call",
-                2,
-                [
-                    heap_con!(Constant::Atom(ct.name(), None)),
-                    heap_integer!(Integer::from(arity))
-                ]
-            ),
-            &ControlInstruction::CallClause(ref ct, arity, _, true, _) => functor!(
-                "execute",
-                2,
-                [
-                    heap_con!(Constant::Atom(ct.name(), None)),
-                    heap_integer!(Integer::from(arity))
-                ]
-            ),
-            &ControlInstruction::Deallocate => vec![heap_atom!("deallocate")],
             &ControlInstruction::JmpBy(_, offset, ..) => {
-                functor!("jmp_by", 1, [heap_integer!(Integer::from(offset))])
+                functor!("jmp_by", [integer(offset)])
+            }
+            &ControlInstruction::Proceed => {
+                functor!("proceed")
             }
-            &ControlInstruction::Proceed => vec![heap_atom!("proceed")],
         }
     }
 }
 
+#[derive(Debug)]
 pub enum IndexingInstruction {
     SwitchOnTerm(usize, usize, usize, usize),
     SwitchOnConstant(usize, IndexMap<Constant, usize>),
@@ -411,34 +440,36 @@ impl From<IndexingInstruction> for Line {
 impl IndexingInstruction {
     pub fn to_functor(&self) -> MachineStub {
         match self {
-            &IndexingInstruction::SwitchOnTerm(vars, constants, lists, structures) => functor!(
-                "switch_on_term",
-                4,
-                [
-                    heap_integer!(Integer::from(vars)),
-                    heap_integer!(Integer::from(constants)),
-                    heap_integer!(Integer::from(lists)),
-                    heap_integer!(Integer::from(structures))
-                ]
-            ),
-            &IndexingInstruction::SwitchOnConstant(constants, _) => functor!(
-                "switch_on_constant",
-                1,
-                [heap_integer!(Integer::from(constants))]
-            ),
-            &IndexingInstruction::SwitchOnStructure(structures, _) => functor!(
-                "switch_on_structure",
-                1,
-                [heap_integer!(Integer::from(structures))]
-            ),
+            &IndexingInstruction::SwitchOnTerm(vars, constants, lists, structures) => {
+                functor!(
+                    "switch_on_term",
+                    [integer(vars),
+                     integer(constants),
+                     integer(lists),
+                     integer(structures)]
+                )
+            }
+            &IndexingInstruction::SwitchOnConstant(constants, _) => {
+                functor!(
+                    "switch_on_constant",
+                    [integer(constants)]
+                )
+            }
+            &IndexingInstruction::SwitchOnStructure(structures, _) => {
+                functor!(
+                    "switch_on_structure",
+                    [integer(structures)]
+                )
+            }
         }
     }
 }
 
-#[derive(Clone)]
+#[derive(Debug, Clone)]
 pub enum FactInstruction {
     GetConstant(Level, Constant, RegType),
     GetList(Level, RegType),
+    GetPartialString(Level, String, RegType, bool),
     GetStructure(ClauseType, usize, RegType),
     GetValue(RegType, usize),
     GetVariable(RegType, usize),
@@ -452,96 +483,106 @@ pub enum FactInstruction {
 impl FactInstruction {
     pub fn to_functor(&self, h: usize) -> MachineStub {
         match self {
-            &FactInstruction::GetConstant(lvl, ref constant, r) => {
-                let mut stub = functor!(
+            &FactInstruction::GetConstant(lvl, ref c, r) => {
+                let lvl_stub = lvl.into_functor();
+                let rt_stub  = reg_type_into_functor(r);
+
+                functor!(
                     "get_constant",
-                    3,
-                    [
-                        heap_str!(h + 4),
-                        heap_con!(constant.clone()),
-                        heap_str!(h + 6)
-                    ]
-                );
-
-                stub.append(&mut lvl.into_functor());
-                stub.append(&mut reg_type_into_functor(r));
-
-                stub
+                    [aux(h, 0), constant(h, c), aux(h, 1)],
+                    [lvl_stub, rt_stub]
+                )
             }
             &FactInstruction::GetList(lvl, r) => {
-                let mut stub = functor!("get_list", 2, [heap_str!(h + 3), heap_str!(h + 5)]);
-                stub.append(&mut lvl.into_functor());
-                stub.append(&mut reg_type_into_functor(r));
+                let lvl_stub = lvl.into_functor();
+                let rt_stub  = reg_type_into_functor(r);
 
-                stub
+                functor!(
+                    "get_list",
+                    [aux(h, 0), aux(h, 1)],
+                    [lvl_stub, rt_stub]
+                )
+            }
+            &FactInstruction::GetPartialString(lvl, ref s, r, has_tail) => {
+                let lvl_stub = lvl.into_functor();
+                let rt_stub  = reg_type_into_functor(r);
+
+                functor!(
+                    "get_partial_string",
+                    [aux(h, 0), string(h, s), aux(h, 1), boolean(has_tail)],
+                    [lvl_stub, rt_stub]
+                )
             }
             &FactInstruction::GetStructure(ref ct, arity, r) => {
-                let mut stub = functor!(
-                    "get_structure",
-                    3,
-                    [
-                        heap_con!(Constant::Atom(ct.name(), None)),
-                        heap_integer!(Integer::from(arity)),
-                        heap_str!(h + 4)
-                    ]
-                );
-                stub.append(&mut reg_type_into_functor(r));
+                let rt_stub = reg_type_into_functor(r);
 
-                stub
+                functor!(
+                    "get_structure",
+                    [clause_name(ct.name()), integer(arity), aux(h, 0)],
+                    [rt_stub]
+                )
             }
             &FactInstruction::GetValue(r, arg) => {
-                let mut stub = functor!(
-                    "get_value",
-                    2,
-                    [heap_str!(h + 3), heap_integer!(Integer::from(arg))]
-                );
-                stub.append(&mut reg_type_into_functor(r));
+                let rt_stub = reg_type_into_functor(r);
 
-                stub
+                functor!(
+                    "get_value",
+                    [aux(h, 0), integer(arg)],
+                    [rt_stub]
+                )
             }
             &FactInstruction::GetVariable(r, arg) => {
-                let mut stub = functor!(
-                    "get_variable",
-                    2,
-                    [heap_str!(h + 3), heap_integer!(Integer::from(arg))]
-                );
-                stub.append(&mut reg_type_into_functor(r));
+                let rt_stub = reg_type_into_functor(r);
 
-                stub
+                functor!(
+                    "get_variable",
+                    [aux(h, 0), integer(arg)],
+                    [rt_stub]
+                )
             }
-            &FactInstruction::UnifyConstant(ref constant) => {
-                functor!("unify_constant", 1, [heap_con!(constant.clone())])
+            &FactInstruction::UnifyConstant(ref c) => {
+                functor!("unify_constant", [constant(h, c)], [])
             }
             &FactInstruction::UnifyLocalValue(r) => {
-                let mut stub = functor!("unify_local_value", 1, [heap_str!(h + 2)]);
-                stub.append(&mut reg_type_into_functor(r));
+                let rt_stub = reg_type_into_functor(r);
 
-                stub
+                functor!(
+                    "unify_local_value",
+                    [aux(h, 0)],
+                    [rt_stub]
+                )
             }
             &FactInstruction::UnifyVariable(r) => {
-                let mut stub = functor!("unify_variable", 1, [heap_str!(h + 2)]);
-                stub.append(&mut reg_type_into_functor(r));
+                let rt_stub = reg_type_into_functor(r);
 
-                stub
+                functor!(
+                    "unify_variable",
+                    [aux(h, 0)],
+                    [rt_stub]
+                )
             }
             &FactInstruction::UnifyValue(r) => {
-                let mut stub = functor!("unify_value", 1, [heap_str!(h + 2)]);
-                stub.append(&mut reg_type_into_functor(r));
+                let rt_stub = reg_type_into_functor(r);
 
-                stub
+                functor!(
+                    "unify_value",
+                    [aux(h, 0)],
+                    [rt_stub]
+                )
             }
             &FactInstruction::UnifyVoid(vars) => {
-                functor!("unify_void", 1, [heap_integer!(Integer::from(vars))])
+                functor!("unify_void", [integer(vars)])
             }
         }
     }
 }
 
-#[derive(Clone)]
+#[derive(Debug, Clone)]
 pub enum QueryInstruction {
     GetVariable(RegType, usize),
     PutConstant(Level, Constant, RegType),
     PutList(Level, RegType),
+    PutPartialString(Level, String, RegType, bool),
     PutStructure(ClauseType, usize, RegType),
     PutUnsafeValue(usize, usize),
     PutValue(RegType, usize),
@@ -558,103 +599,106 @@ impl QueryInstruction {
         match self {
             &QueryInstruction::PutUnsafeValue(norm, arg) => functor!(
                 "put_unsafe_value",
-                2,
-                [
-                    heap_integer!(Integer::from(norm)),
-                    heap_integer!(Integer::from(arg))
-                ]
+                [integer(norm), integer(arg)]
             ),
-            &QueryInstruction::PutConstant(lvl, ref constant, r) => {
-                let mut stub = functor!(
+            &QueryInstruction::PutConstant(lvl, ref c, r) => {
+                let lvl_stub = lvl.into_functor();
+                let rt_stub  = reg_type_into_functor(r);
+
+                functor!(
                     "put_constant",
-                    3,
-                    [
-                        heap_str!(h + 4),
-                        heap_con!(constant.clone()),
-                        heap_str!(h + 6)
-                    ]
-                );
-
-                stub.append(&mut lvl.into_functor());
-                stub.append(&mut reg_type_into_functor(r));
-
-                stub
+                    [aux(h, 0), constant(h, c), aux(h, 1)],
+                    [lvl_stub, rt_stub]
+                )
             }
             &QueryInstruction::PutList(lvl, r) => {
-                let mut stub = functor!("put_list", 2, [heap_str!(h + 3), heap_str!(h + 5)]);
+                let lvl_stub = lvl.into_functor();
+                let rt_stub  = reg_type_into_functor(r);
 
-                stub.append(&mut lvl.into_functor());
-                stub.append(&mut reg_type_into_functor(r));
+                functor!(
+                    "put_list",
+                    [aux(h, 0), aux(h, 1)],
+                    [lvl_stub, rt_stub]
+                )
+            }
+            &QueryInstruction::PutPartialString(lvl, ref s, r, has_tail) => {
+                let lvl_stub = lvl.into_functor();
+                let rt_stub  = reg_type_into_functor(r);
 
-                stub
+                functor!(
+                    "put_partial_string",
+                    [aux(h, 0), string(h, s), aux(h, 1), boolean(has_tail)],
+                    [lvl_stub, rt_stub]
+                )
             }
             &QueryInstruction::PutStructure(ref ct, arity, r) => {
-                let mut stub = functor!(
-                    "put_structure",
-                    3,
-                    [
-                        heap_con!(Constant::Atom(ct.name(), None)),
-                        heap_integer!(Integer::from(arity)),
-                        heap_str!(h + 4)
-                    ]
-                );
+                let rt_stub = reg_type_into_functor(r);
 
-                stub.append(&mut reg_type_into_functor(r));
-                stub
+                functor!(
+                    "put_structure",
+                    [clause_name(ct.name()), integer(arity), aux(h, 0)],
+                    [rt_stub]
+                )
             }
             &QueryInstruction::PutValue(r, arg) => {
-                let mut stub = functor!(
-                    "put_value",
-                    2,
-                    [heap_str!(h + 3), heap_integer!(Integer::from(arg))]
-                );
+                let rt_stub = reg_type_into_functor(r);
 
-                stub.append(&mut reg_type_into_functor(r));
-                stub
+                functor!(
+                    "put_value",
+                    [aux(h, 0), integer(arg)],
+                    [rt_stub]
+                )
             }
             &QueryInstruction::GetVariable(r, arg) => {
-                let mut stub = functor!(
-                    "get_variable",
-                    2,
-                    [heap_str!(h + 3), heap_integer!(Integer::from(arg))]
-                );
+                let rt_stub = reg_type_into_functor(r);
 
-                stub.append(&mut reg_type_into_functor(r));
-                stub
+                functor!(
+                    "get_variable",
+                    [aux(h, 0), integer(arg)],
+                    [rt_stub]
+                )
             }
             &QueryInstruction::PutVariable(r, arg) => {
-                let mut stub = functor!(
-                    "put_variable",
-                    2,
-                    [heap_str!(h + 3), heap_integer!(Integer::from(arg))]
-                );
+                let rt_stub = reg_type_into_functor(r);
 
-                stub.append(&mut reg_type_into_functor(r));
-                stub
+                functor!(
+                    "put_variable",
+                    [aux(h, 0), integer(arg)],
+                    [rt_stub]
+                )
             }
-            &QueryInstruction::SetConstant(ref constant) => {
-                functor!("set_constant", 1, [heap_con!(constant.clone())])
+            &QueryInstruction::SetConstant(ref c) => {
+                functor!("set_constant", [constant(h, c)], [])
             }
             &QueryInstruction::SetLocalValue(r) => {
-                let mut stub = functor!("set_local_value", 1, [heap_str!(h + 2)]);
+                let rt_stub = reg_type_into_functor(r);
 
-                stub.append(&mut reg_type_into_functor(r));
-                stub
+                functor!(
+                    "set_local_value",
+                    [aux(h, 0)],
+                    [rt_stub]
+                )
             }
             &QueryInstruction::SetVariable(r) => {
-                let mut stub = functor!("set_variable", 1, [heap_str!(h + 2)]);
+                let rt_stub = reg_type_into_functor(r);
 
-                stub.append(&mut reg_type_into_functor(r));
-                stub
+                functor!(
+                    "set_variable",
+                    [aux(h, 0)],
+                    [rt_stub]
+                )
             }
             &QueryInstruction::SetValue(r) => {
-                let mut stub = functor!("set_value", 1, [heap_str!(h + 2)]);
+                let rt_stub = reg_type_into_functor(r);
 
-                stub.append(&mut reg_type_into_functor(r));
-                stub
+                functor!(
+                    "set_value",
+                    [aux(h, 0)],
+                    [rt_stub]
+                )
             }
             &QueryInstruction::SetVoid(vars) => {
-                functor!("set_void", 1, [heap_integer!(Integer::from(vars))])
+                functor!("set_void", [integer(vars)])
             }
         }
     }

src/iterators.rs

@@ -1,21 +1,23 @@
-use prolog_parser::ast::*;
+use crate::prolog_parser::ast::*;
 
-use crate::prolog::clause_types::*;
-use crate::prolog::forms::*;
-use crate::prolog::machine::machine_indices::*;
+use crate::clause_types::*;
+use crate::forms::*;
+use crate::machine::machine_indices::*;
 
 use std::cell::Cell;
 use std::collections::VecDeque;
+use std::fmt;
 use std::iter::*;
 use std::rc::Rc;
 use std::vec::Vec;
 
-#[derive(Clone)]
+#[derive(Debug, Clone)]
 pub enum TermRef<'a> {
     AnonVar(Level),
     Cons(Level, &'a Cell<RegType>, &'a Term, &'a Term),
     Constant(Level, &'a Cell<RegType>, &'a Constant),
     Clause(Level, &'a Cell<RegType>, ClauseType, &'a Vec<Box<Term>>),
+    PartialString(Level, &'a Cell<RegType>, String, Option<&'a Term>),
     Var(Level, &'a Cell<VarReg>, Rc<Var>),
 }
 
@@ -27,10 +29,12 @@ impl<'a> TermRef<'a> {
           | TermRef::Constant(lvl, ..)
           | TermRef::Var(lvl, ..)
           | TermRef::Clause(lvl, ..) => lvl,
+          | TermRef::PartialString(lvl, ..) => lvl,
         }
     }
 }
 
+#[derive(Debug)]
 pub enum TermIterState<'a> {
     AnonVar(Level),
     Constant(Level, &'a Cell<RegType>, &'a Constant),
@@ -43,13 +47,67 @@ pub enum TermIterState<'a> {
     ),
     InitialCons(Level, &'a Cell<RegType>, &'a Term, &'a Term),
     FinalCons(Level, &'a Cell<RegType>, &'a Term, &'a Term),
+    PartialString(Level, &'a Cell<RegType>, String, Option<&'a Term>),
     Var(Level, &'a Cell<VarReg>, Rc<Var>),
 }
 
+fn is_partial_string<'a>(
+    head: &'a Term,
+    mut tail: &'a Term,
+) -> Option<(String, Option<&'a Term>)>
+{
+    let mut string =
+        match head {
+            &Term::Constant(_, Constant::Atom(ref atom, _)) if atom.is_char() => {
+                atom.as_str().chars().next().unwrap().to_string()
+            }
+            &Term::Constant(_, Constant::Char(c)) => {
+                c.to_string()
+            }
+            _ => {
+                return None;
+            }
+        };
+
+    while let Term::Cons(_, ref head, ref succ) = tail {
+        match head.as_ref() {
+            &Term::Constant(_, Constant::Atom(ref atom, _)) if atom.is_char() => {
+                string.push(atom.as_str().chars().next().unwrap());
+            }
+            &Term::Constant(_, Constant::Char(c)) => {
+                string.push(c);
+            }
+            _ => {
+                return None;
+            }
+        };
+
+        tail = succ.as_ref();
+    }
+
+    match tail {
+        Term::AnonVar | Term::Var(..) => {
+            return Some((string, Some(tail)));
+        }
+        Term::Constant(_, Constant::EmptyList) => {
+            return Some((string, None));
+        }
+        Term::Constant(_, Constant::String(tail)) => {
+            string += &tail;
+            return Some((string, None));
+        }
+        _ => {
+            return None;
+        }
+    }
+}
+
 impl<'a> TermIterState<'a> {
     pub fn subterm_to_state(lvl: Level, term: &'a Term) -> TermIterState<'a> {
         match term {
-            &Term::AnonVar => TermIterState::AnonVar(lvl),
+            &Term::AnonVar => {
+                TermIterState::AnonVar(lvl)
+            }
             &Term::Clause(ref cell, ref name, ref subterms, ref spec) => {
                 let ct = if let Some(spec) = spec {
                     ClauseType::Op(name.clone(), spec.clone(), CodeIndex::default())
@@ -62,12 +120,17 @@ impl<'a> TermIterState<'a> {
             &Term::Cons(ref cell, ref head, ref tail) => {
                 TermIterState::InitialCons(lvl, cell, head.as_ref(), tail.as_ref())
             }
-            &Term::Constant(ref cell, ref constant) => TermIterState::Constant(lvl, cell, constant),
-            &Term::Var(ref cell, ref var) => TermIterState::Var(lvl, cell, var.clone()),
+            &Term::Constant(ref cell, ref constant) => {
+                TermIterState::Constant(lvl, cell, constant)
+            }
+            &Term::Var(ref cell, ref var) => {
+                TermIterState::Var(lvl, cell, var.clone())
+            }
         }
     }
 }
 
+#[derive(Debug)]
 pub struct QueryIterator<'a> {
     state_stack: Vec<TermIterState<'a>>,
 }
@@ -169,7 +232,9 @@ impl<'a> Iterator for QueryIterator<'a> {
     fn next(&mut self) -> Option<Self::Item> {
         while let Some(iter_state) = self.state_stack.pop() {
             match iter_state {
-                TermIterState::AnonVar(lvl) => return Some(TermRef::AnonVar(lvl)),
+                TermIterState::AnonVar(lvl) => {
+                    return Some(TermRef::AnonVar(lvl));
+                }
                 TermIterState::Clause(lvl, child_num, cell, ct, child_terms) => {
                     if child_num == child_terms.len() {
                         match ct {
@@ -182,7 +247,9 @@ impl<'a> Iterator for QueryIterator<'a> {
                                     lvl => Some(TermRef::Clause(lvl, cell, ct, child_terms)),
                                 }
                             }
-                            _ => return None,
+                            _ => {
+                                return None;
+                            }
                         };
                     } else {
                         self.state_stack.push(TermIterState::Clause(
@@ -192,23 +259,41 @@ impl<'a> Iterator for QueryIterator<'a> {
                             ct,
                             child_terms,
                         ));
+
                         self.push_subterm(lvl.child_level(), child_terms[child_num].as_ref());
                     }
                 }
                 TermIterState::InitialCons(lvl, cell, head, tail) => {
-                    self.state_stack
-                        .push(TermIterState::FinalCons(lvl, cell, head, tail));
+                    if let Some((string, tail)) = is_partial_string(head, tail) {
+                        self.state_stack.push(TermIterState::PartialString(
+                            lvl,
+                            cell,
+                            string,
+                            tail,
+                        ));
 
-                    self.push_subterm(lvl.child_level(), tail);
-                    self.push_subterm(lvl.child_level(), head);
+                        if let Some(tail) = tail {
+                            self.push_subterm(lvl.child_level(), tail);
+                        }
+                    } else {
+                        self.state_stack.push(TermIterState::FinalCons(lvl, cell, head, tail));
+
+                        self.push_subterm(lvl.child_level(), tail);
+                        self.push_subterm(lvl.child_level(), head);
+                    }
+                }
+                TermIterState::PartialString(lvl, cell, string, tail) => {
+                    return Some(TermRef::PartialString(lvl, cell, string, tail));
                 }
                 TermIterState::FinalCons(lvl, cell, head, tail) => {
-                    return Some(TermRef::Cons(lvl, cell, head, tail))
+                    return Some(TermRef::Cons(lvl, cell, head, tail));
                 }
                 TermIterState::Constant(lvl, cell, constant) => {
-                    return Some(TermRef::Constant(lvl, cell, constant))
+                    return Some(TermRef::Constant(lvl, cell, constant));
+                }
+                TermIterState::Var(lvl, cell, var) => {
+                    return Some(TermRef::Var(lvl, cell, var));
                 }
-                TermIterState::Var(lvl, cell, var) => return Some(TermRef::Var(lvl, cell, var)),
             };
         }
 
@@ -216,6 +301,7 @@ impl<'a> Iterator for QueryIterator<'a> {
     }
 }
 
+#[derive(Debug)]
 pub struct FactIterator<'a> {
     state_queue: VecDeque<TermIterState<'a>>,
     iterable_root: bool,
@@ -223,8 +309,7 @@ pub struct FactIterator<'a> {
 
 impl<'a> FactIterator<'a> {
     fn push_subterm(&mut self, lvl: Level, term: &'a Term) {
-        self.state_queue
-            .push_back(TermIterState::subterm_to_state(lvl, term));
+        self.state_queue.push_back(TermIterState::subterm_to_state(lvl, term));
     }
 
     pub fn from_rule_head_clause(terms: &'a Vec<Box<Term>>) -> Self {
@@ -241,7 +326,9 @@ impl<'a> FactIterator<'a> {
 
     fn new(term: &'a Term, iterable_root: bool) -> Self {
         let states = match term {
-            &Term::AnonVar => vec![TermIterState::AnonVar(Level::Root)],
+            &Term::AnonVar => {
+                vec![TermIterState::AnonVar(Level::Root)]
+            }
             &Term::Clause(ref cell, ref name, ref terms, ref fixity) => {
                 let ct = ClauseType::from(name.clone(), terms.len(), fixity.clone());
                 vec![TermIterState::Clause(Level::Root, 0, cell, ct, terms)]
@@ -273,7 +360,9 @@ impl<'a> Iterator for FactIterator<'a> {
     fn next(&mut self) -> Option<Self::Item> {
         while let Some(state) = self.state_queue.pop_front() {
             match state {
-                TermIterState::AnonVar(lvl) => return Some(TermRef::AnonVar(lvl)),
+                TermIterState::AnonVar(lvl) => {
+                    return Some(TermRef::AnonVar(lvl));
+                }
                 TermIterState::Clause(lvl, _, cell, ct, child_terms) => {
                     for child_term in child_terms {
                         self.push_subterm(lvl.child_level(), child_term);
@@ -285,16 +374,27 @@ impl<'a> Iterator for FactIterator<'a> {
                     };
                 }
                 TermIterState::InitialCons(lvl, cell, head, tail) => {
-                    self.push_subterm(Level::Deep, head);
-                    self.push_subterm(Level::Deep, tail);
+                    if let Some((string, tail)) = is_partial_string(head, tail) {
+                        if let Some(tail) = tail {
+                            self.push_subterm(Level::Deep, tail);
+                        }
 
-                    return Some(TermRef::Cons(lvl, cell, head, tail));
+                        return Some(TermRef::PartialString(lvl, cell, string, tail));
+                    } else {
+                        self.push_subterm(Level::Deep, head);
+                        self.push_subterm(Level::Deep, tail);
+
+                        return Some(TermRef::Cons(lvl, cell, head, tail));
+                    }
                 }
                 TermIterState::Constant(lvl, cell, constant) => {
                     return Some(TermRef::Constant(lvl, cell, constant))
                 }
-                TermIterState::Var(lvl, cell, var) => return Some(TermRef::Var(lvl, cell, var)),
-                _ => {}
+                TermIterState::Var(lvl, cell, var) => {
+                    return Some(TermRef::Var(lvl, cell, var));
+                }
+                _ => {
+                }
             }
         }
 
@@ -310,6 +410,7 @@ pub fn breadth_first_iter(term: &Term, iterable_root: bool) -> FactIterator {
     FactIterator::new(term, iterable_root)
 }
 
+#[derive(Debug)]
 pub enum ChunkedTerm<'a> {
     HeadClause(ClauseName, &'a Vec<Box<Term>>),
     BodyTerm(&'a QueryTerm),
@@ -347,6 +448,18 @@ pub struct ChunkedIterator<'a> {
     cut_var_in_head: bool,
 }
 
+impl<'a> fmt::Debug for ChunkedIterator<'a> {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt.debug_struct("ChunkedIterator")
+            .field("chunk_num", &self.chunk_num)
+            // Hacky solution.
+            .field("iter", &"Box<dyn Iterator<Item = ChunkedTerm<'a>> + 'a>")
+            .field("deep_cut_encountered", &self.deep_cut_encountered)
+            .field("cut_var_in_head", &self.cut_var_in_head)
+            .finish()
+    }
+}
+
 type ChunkedIteratorItem<'a> = (usize, usize, Vec<ChunkedTerm<'a>>);
 type RuleBodyIteratorItem<'a> = (usize, usize, Vec<&'a QueryTerm>);
 

src/l0/ast.rs

@@ -1,51 +0,0 @@
-use std::cell::{Cell};
-use std::vec::{Vec};
-
-pub type Var = String;
-
-pub type Atom = String;
-
-#[derive(Debug)]
-pub enum TopLevel {
-    Fact(Term),
-    Query(Term)
-}
-
-#[derive(Debug)]
-pub enum Term {
-    Atom(Cell<usize>, Atom),
-    Clause(Cell<usize>, Atom, Vec<Box<Term>>),
-    Var(Cell<usize>, Var)
-}
-
-pub enum FactInstruction {
-    GetStructure(Atom, usize, usize),
-    UnifyVariable(usize),
-    UnifyValue(usize)
-}
-
-pub enum QueryInstruction {    
-    PutStructure(Atom, usize, usize),
-    SetVariable(usize),
-    SetValue(usize),    
-}
-
-pub type CompiledFact = Vec<FactInstruction>;
-
-pub type CompiledQuery = Vec<QueryInstruction>;
-
-#[derive(Clone, Copy, PartialEq)]
-pub enum Addr {
-    HeapCell(usize),
-    RegNum(usize)
-}
-
-impl Term {
-    pub fn set_cell(&self, cell_num: usize) {
-        match self {
-            &Term::Atom(ref cell, _) => cell.set(cell_num),
-            &Term::Clause(ref cell, _, _) => cell.set(cell_num),
-            &Term::Var(ref cell, _) => cell.set(cell_num)
-        };
-    }
-}

src/l0/codegen.rs

@@ -1,126 +0,0 @@
-use l0::ast::{Atom, Term, FactInstruction, QueryInstruction, Var};
-use l0::iterators::{BreadthFirstIterator, PostOrderIterator};
-
-use std::collections::{HashSet};
-use std::fmt;
-use std::vec::{Vec};
-
-impl fmt::Display for QueryInstruction {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self {
-            &QueryInstruction::PutStructure(ref a, ref s, ref r) =>
-                write!(f, "put_structure {}/{}, X{}", a, s, r),
-            &QueryInstruction::SetVariable(ref r) =>
-                write!(f, "set_variable X{}", r),
-            &QueryInstruction::SetValue(ref r) =>
-                write!(f, "set_value X{}", r),
-        }
-    }
-}
-
-impl fmt::Display for FactInstruction {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self {
-            &FactInstruction::GetStructure(ref a, ref s, ref r) =>
-                write!(f, "get_structure {}/{}, X{}", a, s, r),
-            &FactInstruction::UnifyVariable(ref r) =>
-                write!(f, "unify_variable X{}", r),
-            &FactInstruction::UnifyValue(ref r) =>
-                write!(f, "unify_value X{}", r)
-        }
-    }
-}
-
-pub trait CompilationTarget<'a> {
-    type Iterator : Iterator<Item=&'a Term>;
-    
-    fn iter(term: &'a Term) -> Self::Iterator;
-
-    fn to_structure(name: Atom, arity: usize, cell_num: usize) -> Self;
-    fn to_value(cell_num: usize) -> Self;
-    fn to_variable(cell_num: usize) -> Self;
-}
-
-impl<'a> CompilationTarget<'a> for FactInstruction {
-    type Iterator = BreadthFirstIterator<'a>;
-    
-    fn iter(term: &'a Term) -> Self::Iterator {
-        term.breadth_first_iter()
-    }
-
-    fn to_structure(name: Atom, arity: usize, cell_num: usize) -> Self {
-        FactInstruction::GetStructure(name, arity, cell_num)
-    }
-
-    fn to_value(cell_num: usize) -> Self {
-        FactInstruction::UnifyValue(cell_num)
-    }
-
-    fn to_variable(cell_num: usize) -> Self {
-        FactInstruction::UnifyVariable(cell_num)
-    }
-}
-
-impl<'a> CompilationTarget<'a> for QueryInstruction {
-    type Iterator = PostOrderIterator<'a>;
-
-    fn iter(term: &'a Term) -> Self::Iterator {
-        term.post_order_iter()
-    }
-
-    fn to_structure(name: Atom, arity: usize, cell_num: usize) -> Self {
-        QueryInstruction::PutStructure(name, arity, cell_num)
-    }
-
-    fn to_value(cell_num: usize) -> Self {
-        QueryInstruction::SetValue(cell_num)
-    }
-
-    fn to_variable(cell_num: usize) -> Self {
-        QueryInstruction::SetVariable(cell_num)
-    }
-}
-
-fn subterm_to_instr<'a, Target>(subterm:  &'a Term,
-                                bindings: &mut HashSet<&'a Var>)
-                                -> Target
-    where Target: CompilationTarget<'a>
-{
-    match subterm {
-        &Term::Atom(ref cell_num, _) =>
-            Target::to_value(cell_num.get()),
-        &Term::Var(ref cell_num, ref atom) if bindings.contains(atom) =>
-            Target::to_value(cell_num.get()),
-        &Term::Var(ref cell_num, ref atom) => {
-            bindings.insert(atom);
-            Target::to_variable(cell_num.get())
-        },
-        &Term::Clause(ref cell_num, _, _) =>
-            Target::to_value(cell_num.get())
-    }
-}
-
-pub fn compile_target<'a, Target>(term: &'a Term) -> Vec<Target>
-    where Target: CompilationTarget<'a>
-{
-    let mut iter     = Target::iter(term);
-    let mut target   = Vec::<Target>::new();
-    let mut bindings = HashSet::new();
-
-    while let Some(term) = iter.next() {
-        match term {
-            &Term::Atom(ref cell_num, ref atom) =>
-                target.push(Target::to_structure(atom.clone(), 0, cell_num.get())),
-            &Term::Clause(ref cell_num, ref atom, ref terms) => {
-                target.push(Target::to_structure(atom.clone(), 0, cell_num.get()));
-
-                for subterm in terms {
-                    target.push(subterm_to_instr(subterm.as_ref(), &mut bindings));
-                }
-            },
-            _ => {},
-        };
-    }
-
-    target
-}

src/l0/iterators.rs

@@ -1,98 +0,0 @@
-use l0::ast::{Term};
-
-use std::collections::{VecDeque};
-use std::vec::{Vec};
-
-enum DepthFirstIteratorState<'a> {        
-    // child no., the containing clause, its vector.
-    Clause(usize, &'a Term, &'a Vec<Box<Term>>),
-    NonClause(&'a Term)
-}
-
-pub struct PostOrderIterator<'a> {
-    state_stack: Vec<DepthFirstIteratorState<'a>>        
-}
-
-impl<'a> PostOrderIterator<'a> {
-    fn push_clause(&mut self,
-                   child_num: usize,
-                   term: &'a Term,
-                   child_terms: &'a Vec<Box<Term>>)
-    {
-        self.state_stack.push(DepthFirstIteratorState::Clause(child_num,
-                                                              term,
-                                                              child_terms));
-    }
-
-    fn render_new_state(term: &'a Term) -> DepthFirstIteratorState<'a> {
-        match term {
-            &Term::Clause(_, _, ref child_terms) =>
-                DepthFirstIteratorState::Clause(0, term, child_terms),
-            _ => DepthFirstIteratorState::NonClause(term)
-        }
-    }
-
-    fn push_term(&mut self, term: &'a Term) {
-        self.state_stack.push(Self::render_new_state(term));
-    }
-}
-
-impl<'a> Iterator for PostOrderIterator<'a> {
-    type Item = &'a Term;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        while let Some(iter_state) = self.state_stack.pop() {
-            match iter_state {
-                DepthFirstIteratorState::Clause(child_num, term, child_terms) => {                    
-                    if child_num == child_terms.len() {
-                        return Some(term);
-                    } else {
-                        self.push_clause(child_num + 1, term, child_terms);
-                        self.push_term(child_terms[child_num].as_ref());
-                    }
-                },
-                DepthFirstIteratorState::NonClause(term) => return Some(term),
-            };
-        }
-
-        None
-    }
-}
-
-pub struct BreadthFirstIterator<'a> {
-    state_queue : VecDeque<&'a Term>
-}
-
-impl<'a> Iterator for BreadthFirstIterator<'a> {
-    type Item = &'a Term;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        if let Some(term) = self.state_queue.pop_front() {            
-            if let &Term::Clause(_, _, ref child_terms) = term {
-                for term in child_terms {
-                    self.state_queue.push_back(term);
-                }
-
-                return Some(term);
-            }
-
-            return Some(term);
-        }
-
-        None
-    }
-}
-    
-impl<'a> Term {
-    pub fn post_order_iter(&'a self) -> PostOrderIterator<'a> {
-        let initial_state = PostOrderIterator::render_new_state(self);
-        PostOrderIterator { state_stack: vec![initial_state] }
-    }
-
-    pub fn breadth_first_iter(&'a self) -> BreadthFirstIterator<'a> {
-        let mut queue = VecDeque::new();
-        queue.push_back(self);
-        
-        BreadthFirstIterator { state_queue: queue }
-    }
-}

src/l0/l0_parser.lalrpop

@@ -1,31 +0,0 @@
-use std::cell::{Cell};
-use l0::ast::{Atom, Term, TopLevel, Var};
-
-grammar;
-
-pub TopLevel: TopLevel = {
-    "?-" <t:Term> "." => TopLevel::Query(t),
-    <t:Term> "."      => TopLevel::Fact(t),
-};
-
-Atom : Atom = {
-     r"[a-z][a-z0-9_]*" => <>.trim().to_string(),
-};
-
-Var : Var = {
-     r"[A-Z][a-z0-9_]*" => <>.trim().to_string(),
-};	
-
-BoxedTerm : Box<Term> = {
-     <t:Term> => Box::new(t),
-};
-
-Term : Term = {
-     <a:Atom> "(" <ts: (<BoxedTerm> ",")*> <t:BoxedTerm> ")" => {
-     	      let mut ts = ts;
-     	      ts.push(t);
-	      Term::Clause(Cell::new(0), a, ts)
-     },
-     <Atom> => Term::Atom(Cell::new(0), <>),
-     <Var>  => Term::Var(Cell::new(0), <>),
-};

src/l0/machine.rs

@@ -1,238 +0,0 @@
-use l0::ast::{Addr, Atom, CompiledFact, FactInstruction, QueryInstruction};
-
-use std::vec::{Vec};
-
-#[derive(Clone)]
-enum HeapCell {
-    NamedStr(usize, Atom),
-    Ref(usize),
-    Str(usize),
-}
-
-#[derive(Clone, Copy)]
-enum MachineMode {
-    Read,
-    Write
-}
-
-type Heap = Vec<HeapCell>;
-
-type Registers = Vec<HeapCell>;
-
-pub struct Machine {
-    h : usize,
-    s : usize,
-    pub fail : bool,
-    heap : Heap,
-    mode : MachineMode,
-    pub program : Option<CompiledFact>,
-    registers : Registers
-}
-
-impl Machine {
-    pub fn new() -> Machine {
-        Machine { h : 0,
-                  s : 0,
-                  fail : false,
-                  heap : Vec::with_capacity(256),
-                  mode : MachineMode::Write,
-                  program : None,
-                  registers : vec![HeapCell::Ref(0); 33] }
-    }
-    
-    fn lookup(&self, a: Addr) -> &HeapCell {
-        match a {
-            Addr::HeapCell(hc) => &self.heap[hc],
-            Addr::RegNum(reg)  => &self.registers[reg]
-        }
-    }
-
-    fn deref(&self, a: Addr) -> Addr {
-        let mut a = a;
-
-        loop {
-            if let &HeapCell::Ref(value) = self.lookup(a) {
-                if let Addr::HeapCell(av) = a {
-                    if value != av {
-                        a = Addr::HeapCell(value);
-                        continue;
-                    }
-                }
-            }
-
-            return a;
-        };
-    }
-
-    fn is_unbound(hc: &HeapCell, index: usize) -> bool {
-        match hc {
-            &HeapCell::Ref(r) => r == index,
-            _ => false
-        }
-    }
-    
-    //TODO: try to compress this function. currently it is dog shit.
-    fn bind(&mut self, a: Addr, val: usize) {
-        let mut a = a;
-        
-        loop {
-            match a {
-                Addr::RegNum(reg) => {
-                    if let HeapCell::Ref(hc) = self.registers[reg] {
-                        a = Addr::HeapCell(hc);
-                    } else if Machine::is_unbound(&self.heap[val], val) {
-                        self.heap[val] = self.registers[reg].clone();
-                        break;
-                    } else {
-                        self.fail = true;
-                        break;
-                    }                        
-                },
-                Addr::HeapCell(hc) if Machine::is_unbound(&self.heap[hc], hc) => {
-                    self.heap[hc] = HeapCell::Ref(val);
-                    break;
-                },
-                Addr::HeapCell(hc) if Machine::is_unbound(&self.heap[val], val) => {                
-                    self.heap[val] = HeapCell::Ref(hc);
-                    break;
-                },
-                _ => {
-                    self.fail = true;                    
-                    break;
-                }
-            };
-        }
-    }
-
-    fn unify(&mut self, a1: Addr, a2: Addr) {
-        let mut pdl : Vec<Addr> = vec![a1, a2];
-
-        self.fail = false;
-
-        while !(pdl.is_empty() || self.fail) {
-            let d1 = self.deref(pdl.pop().unwrap());
-            let d2 = self.deref(pdl.pop().unwrap());
-
-            if d1 != d2 {
-                match (self.lookup(d1), self.lookup(d2)) {
-                    (&HeapCell::Ref(hc), _) =>
-                        self.bind(d2, hc),
-                    (_, &HeapCell::Ref(hc)) =>
-                        self.bind(d1, hc),
-                    (&HeapCell::Str(a1), &HeapCell::Str(a2)) => {
-                        let r1 = &self.heap[a1];
-                        let r2 = &self.heap[a2];
-
-                        if let &HeapCell::NamedStr(n1, ref f1) = r1 {
-                            if let &HeapCell::NamedStr(n2, ref f2) = r2 {
-                                if n1 == n2 && *f1 == *f2 {
-                                    for i in 1 .. n1 {
-                                        pdl.push(Addr::HeapCell(a1 + i));
-                                        pdl.push(Addr::HeapCell(a2 + i));
-                                    }
-
-                                    continue;
-                                }
-                            }
-                        }
-
-                        self.fail = true;
-                    },
-                    _ => self.fail = true,
-                };
-            }
-        }
-    }    
-
-    pub fn execute_query_instr<'a, 'b : 'a>(&'a mut self, instr: &'b QueryInstruction) {
-        match instr {
-            &QueryInstruction::PutStructure(ref name, arity, reg) => {
-                self.heap.push(HeapCell::Str(self.h + 1));
-                self.heap.push(HeapCell::NamedStr(arity, name.clone()));
-
-                self.registers[reg] = self.heap[self.h].clone();
-
-                self.h += 2;
-            },
-            &QueryInstruction::SetVariable(reg) => {
-                self.heap.push(HeapCell::Ref(self.h));
-                self.registers[reg] = self.heap[self.h].clone();
-
-                self.h += 1;
-            },
-            &QueryInstruction::SetValue(reg) => {
-                self.heap.push(self.registers[reg].clone());
-                self.h += 1;
-            },
-        }
-    }
-    
-    pub fn execute_fact_instr<'a, 'b : 'a>(&'a mut self, instr: &'b FactInstruction) {
-        match instr {
-            &FactInstruction::GetStructure(ref name, arity, reg) => {
-                let addr = self.deref(Addr::RegNum(reg));
-
-                match self.lookup(addr) {
-                    &HeapCell::Str(a) => {
-                        let result = &self.heap[a];
-
-                        if let &HeapCell::NamedStr(named_arity, ref named_str) = result {
-                            if arity == named_arity && *name == *named_str {
-                                self.s = a + 1;
-                                self.mode = MachineMode::Read;
-                            } else {
-                                self.fail = true;
-                            }
-                        }
-                    },
-                    &HeapCell::Ref(r) => {
-                        self.heap.push(HeapCell::Str(self.h + 1));
-                        self.heap.push(HeapCell::NamedStr(arity, name.clone()));
-
-                        let h = self.h;
-
-                        self.bind(Addr::HeapCell(r), h);
-
-                        self.h += 2;
-                        self.mode = MachineMode::Write;
-                    },
-                    _ => {
-                        self.fail = true;
-                    }
-                };
-            },
-            &FactInstruction::UnifyVariable(reg) => {
-                match self.mode {
-                    MachineMode::Read  => self.registers[reg] = self.heap[self.s].clone(),
-                    MachineMode::Write => {
-                        self.heap.push(HeapCell::Ref(self.h));
-                        self.registers[reg] = self.heap[self.h].clone();
-                        self.h += 1;
-                    }
-                };
-
-                self.s += 1;
-            },
-            &FactInstruction::UnifyValue(reg) => {
-                let s = self.s;
-
-                match self.mode {
-                    MachineMode::Read  => self.unify(Addr::RegNum(reg), Addr::HeapCell(s)),
-                    MachineMode::Write => {
-                        self.heap.push(self.registers[reg].clone());
-                        self.h += 1;
-                    }
-                };
-                
-                self.s += 1;
-            }
-        }
-    }
-    
-    pub fn reset_heap(&mut self) {
-        let program = self.program.take();
-
-        *self = Machine::new();
-        self.program = program;
-    }    
-}

src/l0/mod.rs

@@ -1,7 +0,0 @@
-mod l0_parser;
-
-pub mod ast;
-pub mod iterators;
-pub mod parser;
-pub mod codegen;
-pub mod machine;

src/l0/parser.rs

@@ -1,52 +0,0 @@
-use l0::ast::{Term, TopLevel, Var};
-use l0::l0_parser::{parse_TopLevel};
-
-use std::collections::{HashMap};
-
-extern crate lalrpop_util as __lalrpop_util;
-
-pub type ParseResult<'a> =
-    Result<TopLevel, __lalrpop_util::ParseError<usize,(usize, &'a str),()>>;
-
-pub fn parse_top_level<'a>(input: &'a str) -> ParseResult {
-    let result = parse_TopLevel(&*input);
-    
-    if let Ok(result) = result {
-        return Ok(mark_cells(result));
-    }
-
-    result
-}
-
-#[inline]
-fn mark_cells(tl: TopLevel) -> TopLevel {
-    match tl {
-        TopLevel::Fact(term) => TopLevel::Fact(mark_term_cells(term)),
-        TopLevel::Query(term) => TopLevel::Query(mark_term_cells(term))            
-    }
-}
-    
-fn mark_term_cells(term: Term) -> Term {
-    let mut cell_num = 1;    
-    
-    {
-        let mut bindings: HashMap<&Var, usize> = HashMap::new();
-        let mut iter = term.breadth_first_iter();
-    
-        while let Some(term) = iter.next() {
-            if let &Term::Var(ref cell, ref var) = term {
-                let cell_num_in_map = bindings.entry(var).or_insert(cell_num);
-                
-                if *cell_num_in_map != cell_num {                    
-                    cell.set(*cell_num_in_map);
-                    continue;
-                }
-            }
-
-            term.set_cell(cell_num);
-            cell_num += 1;
-        }
-    }
-
-    term
-}

src/l1/ast.rs

@@ -1,123 +0,0 @@
-use std::cell::Cell;
-use std::fmt;
-use std::vec::Vec;
-
-pub type Var = String;
-
-pub type Atom = String;
-
-pub enum TopLevel {
-    Fact(Term),
-    Query(Term)
-}
-
-#[derive(Clone, Copy)]
-pub enum Level {
-    Shallow, Deep
-}
-
-impl fmt::Display for Level {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self {
-            &Level::Shallow => write!(f, "A"),
-            &Level::Deep => write!(f, "X")
-        }
-    }
-}
-
-#[derive(Clone, Copy)]
-pub enum Reg {
-    ArgAndNorm(usize, usize),
-    Norm(usize)
-}
-
-impl Reg {
-    pub fn has_arg(&self) -> bool {
-        match self {
-            &Reg::ArgAndNorm(_, _) => true,
-            _ => false
-        }
-    }
-
-    pub fn norm(&self) -> usize {
-        match self {
-            &Reg::ArgAndNorm(_, norm) | &Reg::Norm(norm) => norm
-        }
-    }
-}
-
-pub enum Term {
-    Atom(Cell<usize>, Atom),
-    Clause(Cell<usize>, Atom, Vec<Box<Term>>),
-    Var(Cell<Reg>, Var)
-}
-
-pub enum TermRef<'a> {
-    Atom(Level, &'a Cell<usize>, &'a Atom),
-    Clause(Level, &'a Cell<usize>, &'a Atom, &'a Vec<Box<Term>>),
-    Var(Level, &'a Cell<Reg>, &'a Var)
-}
-
-#[derive(Clone)]
-pub enum FactInstruction {
-    GetStructure(Level, Atom, usize, usize),
-    GetValue(usize, usize),
-    GetVariable(usize, usize),
-    Proceed,
-    UnifyVariable(usize),
-    UnifyValue(usize)
-}
-
-pub enum QueryInstruction {
-    Call(Atom, usize),
-    PutStructure(Level, Atom, usize, usize),
-    PutValue(usize, usize),
-    PutVariable(usize, usize),
-    SetVariable(usize),
-    SetValue(usize),
-}
-
-pub type CompiledFact = Vec<FactInstruction>;
-
-pub type CompiledQuery = Vec<QueryInstruction>;
-
-#[derive(Clone, Copy, PartialEq)]
-pub enum Addr {
-    HeapCell(usize),
-    RegNum(usize)
-}
-
-#[derive(Clone)]
-pub enum HeapCellValue {
-    NamedStr(usize, Atom),
-    Ref(usize),
-    Str(usize),
-}
-
-pub type Heap = Vec<HeapCellValue>;
-
-pub type Registers = Vec<HeapCellValue>;
-
-impl Term {
-    pub fn subterms(&self) -> usize {
-        match self {
-            &Term::Clause(_, _, ref terms) => terms.len(),
-            _ => 1
-        }
-    }
-
-    pub fn name(&self) -> &Atom {
-        match self {
-            &Term::Atom(_, ref atom)
-            | &Term::Var(_, ref atom)
-            | &Term::Clause(_, ref atom, _) => atom
-        }
-    }
-
-    pub fn arity(&self) -> usize {
-        match self {
-            &Term::Atom(_, _) | &Term::Var(_, _) => 0,
-            &Term::Clause(_, _, ref child_terms) => child_terms.len()
-        }
-    }
-}

src/l1/codegen.rs

@@ -1,312 +0,0 @@
-use l1::ast::{Atom, CompiledFact, CompiledQuery, FactInstruction,
-              Level, QueryInstruction, Reg, Term, TermRef, Var};
-use l1::iterators::{FactIterator, QueryIterator};
-
-use std::cell::Cell;
-use std::collections::HashMap;
-use std::fmt;
-use std::vec::Vec;
-
-impl fmt::Display for QueryInstruction {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self {
-            &QueryInstruction::Call(ref name, ref arity) =>
-                write!(f, "call {}/{}", name, arity),
-            &QueryInstruction::PutStructure(ref lvl, ref a, ref s, ref r) =>
-                write!(f, "put_structure {}/{}, {}{}", a, s, lvl, r),
-            &QueryInstruction::PutValue(ref a, ref x) =>
-                write!(f, "put_value X{}, A{}", x, a),
-            &QueryInstruction::PutVariable(ref a, ref x) =>
-                write!(f, "put_variable X{}, A{}", x, a),
-            &QueryInstruction::SetVariable(ref r) =>
-                write!(f, "set_variable X{}", r),
-            &QueryInstruction::SetValue(ref r) =>
-                write!(f, "set_value X{}", r),
-        }
-    }
-}
-
-impl fmt::Display for FactInstruction {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self {
-            &FactInstruction::GetStructure(ref lvl, ref a, ref s, ref r) =>
-                write!(f, "get_structure {}/{}, {}{}", a, s, lvl, r),
-            &FactInstruction::GetValue(ref a, ref x) =>
-                write!(f, "get_value X{}, A{}", x, a),
-            &FactInstruction::GetVariable(ref a, ref x) =>
-                write!(f, "get_variable X{}, A{}", x, a),
-            &FactInstruction::Proceed =>
-                write!(f, "proceed"),
-            &FactInstruction::UnifyVariable(ref r) =>
-                write!(f, "unify_variable X{}", r),
-            &FactInstruction::UnifyValue(ref r) =>
-                write!(f, "unify_value X{}", r)
-        }
-    }
-}
-
-struct TermMarker<'a> {    
-    bindings: HashMap<&'a Var, Reg>,
-    arg_c:    usize,
-    norm_c:   usize
-}
-
-impl<'a> TermMarker<'a> {
-    fn new(term: &'a Term) -> TermMarker<'a> {
-        TermMarker { bindings: HashMap::new(),
-                     arg_c:    1,
-                     norm_c:   term.subterms() + 1 }
-    }
-
-    fn contains_var(&self, var: &'a Var) -> bool {
-        self.bindings.contains_key(var)
-    }
-
-    fn get(&self, var: &'a Var) -> Reg {
-        *self.bindings.get(var).unwrap()
-    }
-
-    fn insert(&mut self, var: &'a Var, r: Reg) {
-        self.bindings.insert(var, r);
-    }
-    
-    fn mark_non_var(&mut self, lvl: Level, cell: &Cell<usize>) {
-        if cell.get() == 0 {            
-            match lvl {
-                Level::Deep => {
-                    let norm = self.norm_c;
-                    self.norm_c += 1;
-                    cell.set(norm);
-                },            
-                Level::Shallow => {
-                    let arg = self.arg_c;
-                    self.arg_c += 1;
-                    cell.set(arg);
-                }
-            };
-        }
-    }
-
-    fn mark_var(&mut self, lvl: Level, var: &'a Var) -> Reg {
-        if self.contains_var(var) {
-            let reg = self.get(var);
-
-            match lvl {
-                Level::Deep => Reg::Norm(reg.norm()),
-                Level::Shallow if reg.has_arg() => {
-                    let arg = self.arg_c;
-                    self.arg_c += 1;
-                    
-                    Reg::ArgAndNorm(arg, reg.norm())
-                },
-                Level::Shallow => {
-                    let norm = reg.norm();
-                    let reg  = Reg::ArgAndNorm(self.arg_c, norm);
-
-                    self.arg_c += 1;
-                    self.insert(var, reg);
-
-                    reg
-                }
-            }
-        } else {
-            let reg = match lvl {
-                Level::Deep    => Reg::Norm(self.norm_c),
-                Level::Shallow => {
-                    let reg = Reg::ArgAndNorm(self.arg_c, self.norm_c);
-                    self.arg_c += 1;
-                    reg
-                }
-            };
-
-            self.norm_c += 1;
-            self.insert(var, reg);
-            reg
-        }
-    }
-}
-
-trait CompilationTarget<'a> {
-    type Iterator : Iterator<Item=TermRef<'a>>;
-
-    fn iter(&'a Term) -> Self::Iterator;
-
-    fn to_structure(Level, Atom, usize, usize) -> Self;
-
-    fn argument_to_variable(usize, usize) -> Self;
-    fn argument_to_value(usize, usize) -> Self;
-    fn subterm_to_variable(usize) -> Self;
-    fn subterm_to_value(usize) -> Self;
-
-    fn clause_arg_to_instr(usize) -> Self;
-}
-
-impl<'a> CompilationTarget<'a> for FactInstruction {
-    type Iterator = FactIterator<'a>;
-
-    fn iter(term: &'a Term) -> Self::Iterator {
-        term.breadth_first_iter()
-    }
-
-    fn to_structure(lvl: Level, atom: Atom, arity: usize, cell_num: usize) -> Self {        
-        FactInstruction::GetStructure(lvl, atom, arity, cell_num)
-    }
-
-    fn argument_to_variable(arg: usize, val: usize) -> Self {
-        FactInstruction::GetVariable(arg, val)
-    }
-
-    fn argument_to_value(arg: usize, val: usize) -> Self {
-        FactInstruction::GetValue(arg, val)
-    }
-
-    fn subterm_to_variable(val: usize) -> Self {
-        FactInstruction::UnifyVariable(val)
-    }
-
-    fn subterm_to_value(val: usize) -> Self {
-        FactInstruction::UnifyValue(val)
-    }
-
-    fn clause_arg_to_instr(val: usize) -> Self {
-        FactInstruction::UnifyVariable(val)
-    }
-}
-
-impl<'a> CompilationTarget<'a> for QueryInstruction {
-    type Iterator = QueryIterator<'a>;
-
-    fn iter(term: &'a Term) -> Self::Iterator {
-        term.post_order_iter()
-    }
-
-    fn to_structure(lvl: Level, atom: Atom, arity: usize, cell_num: usize) -> Self {
-        QueryInstruction::PutStructure(lvl, atom, arity, cell_num)
-    }
-
-    fn argument_to_variable(arg: usize, val: usize) -> Self {
-        QueryInstruction::PutVariable(arg, val)
-    }
-
-    fn argument_to_value(arg: usize, val: usize) -> Self {
-        QueryInstruction::PutValue(arg, val)
-    }
-
-    fn subterm_to_variable(val: usize) -> Self {
-        QueryInstruction::SetVariable(val)
-    }
-
-    fn subterm_to_value(val: usize) -> Self {
-        QueryInstruction::SetValue(val)
-    }
-    
-    fn clause_arg_to_instr(val: usize) -> Self {
-        QueryInstruction::SetValue(val)
-    }
-}
-
-fn to_structure<'a, Target>(tm: &mut TermMarker<'a>,
-                            lvl: Level,
-                            name: &'a Atom,
-                            cell: &'a Cell<usize>,
-                            arity: usize)
-                            -> Target
-    where Target: CompilationTarget<'a>
-{
-    tm.mark_non_var(lvl, cell);
-    Target::to_structure(lvl, name.clone(), arity, cell.get())
-}
-
-fn non_var_subterm<'a, Target>(tm: &mut TermMarker<'a>, cell: &'a Cell<usize>)
-                               -> Target
-    where Target: CompilationTarget<'a>
-{
-    tm.mark_non_var(Level::Deep, cell);
-    Target::clause_arg_to_instr(cell.get())
-}
-
-fn var_term<'a, Target>(tm: &mut TermMarker<'a>,
-                        lvl: Level,
-                        cell: &'a Cell<Reg>,
-                        var: &'a Var)
-                        -> Target
-    where Target: CompilationTarget<'a>
-{
-    if !tm.contains_var(var) {
-        let reg = tm.mark_var(lvl, var);
-        cell.set(reg);
-        
-        match reg {
-            Reg::ArgAndNorm(arg, norm) =>
-                Target::argument_to_variable(arg, norm),
-            Reg::Norm(norm) =>
-                Target::subterm_to_variable(norm)
-        }
-    } else {
-        let reg = tm.mark_var(lvl, var);
-        cell.set(reg);
-        
-        match reg {
-            Reg::ArgAndNorm(arg, norm) =>
-                Target::argument_to_value(arg, norm),
-            Reg::Norm(norm) =>
-                Target::subterm_to_value(norm)
-        }
-    }
-}
-
-fn subterm_to_instr<'a, Target>(tm: &mut TermMarker<'a>, subterm: &'a Term)
-                                -> Target
-    where Target: CompilationTarget<'a>
-{
-    match subterm {
-        &Term::Atom(ref cell, _) | &Term::Clause(ref cell, _, _) =>
-            non_var_subterm(tm, cell),
-        &Term::Var(ref cell, ref var) =>
-            var_term(tm, Level::Deep, cell, var)
-    }
-}
-
-fn compile_target<'a, Target>(term: &'a Term) -> Vec<Target>
-    where Target: CompilationTarget<'a>
-{
-    let iter       = Target::iter(term);
-    let mut target = Vec::<Target>::new();
-    let mut marker = TermMarker::new(term);
-    
-    for term in iter {
-        match term {
-            TermRef::Atom(lvl, term, atom) =>
-                target.push(to_structure(&mut marker, lvl, atom, term, 0)),
-            TermRef::Clause(lvl, term, atom, terms) => {
-                target.push(to_structure(&mut marker, lvl, atom, term, terms.len()));
-
-                for subterm in terms {
-                    target.push(subterm_to_instr(&mut marker, subterm.as_ref()));
-                }
-            },
-            TermRef::Var(lvl @ Level::Shallow, ref cell, ref var) =>
-                target.push(var_term(&mut marker, lvl, cell, var)),
-            _ => {}
-        };
-    }
-
-    target
-}
-
-pub fn compile_fact(term: &Term) -> CompiledFact {
-    let mut compiled_fact = compile_target(term);
-
-    compiled_fact.push(FactInstruction::Proceed);
-    compiled_fact
-}
-
-pub fn compile_query<'a>(term: &'a Term) -> CompiledQuery {
-    let mut compiled_query = compile_target(term);
-
-    if let &Term::Clause(_, ref atom, ref terms) = term {
-        compiled_query.push(QueryInstruction::Call(atom.clone(), terms.len()));
-    }
-
-    compiled_query
-}

src/l1/iterators.rs

@@ -1,175 +0,0 @@
-use l1::ast::{Atom, Level, Reg, Term, TermRef, Var};
-
-use std::cell::Cell;
-use std::collections::VecDeque;
-use std::vec::Vec;
-
-enum IteratorState<'a> {
-    Atom(Level, &'a Cell<usize>, &'a Atom),
-    Clause(Level, usize, &'a Cell<usize>, &'a Atom, &'a Vec<Box<Term>>),
-    IsolatedAtom(&'a Cell<usize>, &'a Atom),
-    IsolatedVar(&'a Cell<Reg>, &'a Var),
-    RootClause(usize, &'a Vec<Box<Term>>),
-    Var(Level, &'a Cell<Reg>, &'a Var)
-}
-
-impl<'a> IteratorState<'a> {
-    fn to_state(lvl: Level, term: &'a Term) -> IteratorState<'a>
-    {
-        match term {
-            &Term::Atom(ref cell, ref atom) =>
-                IteratorState::Atom(lvl, cell, atom),
-            &Term::Clause(ref cell, ref atom, ref child_terms) =>
-                IteratorState::Clause(lvl, 0, cell, atom, child_terms),
-            &Term::Var(ref cell, ref var) =>
-                IteratorState::Var(lvl, cell, var)
-        }
-    }
-}
-
-pub struct QueryIterator<'a> {
-    state_stack: Vec<IteratorState<'a>>
-}
-
-impl<'a> QueryIterator<'a> {
-    fn push_clause(&mut self,
-                   lvl: Level,
-                   child_num: usize,
-                   cell: &'a Cell<usize>,
-                   name: &'a Atom,
-                   child_terms: &'a Vec<Box<Term>>)
-    {
-        self.state_stack.push(IteratorState::Clause(lvl,
-                                                    child_num,
-                                                    cell,
-                                                    name,
-                                                    child_terms));
-    }
-
-    fn push_root_clause(&mut self,
-                        child_num: usize,                        
-                        child_terms: &'a Vec<Box<Term>>)
-    {
-        self.state_stack.push(IteratorState::RootClause(child_num, child_terms));
-    }
-
-    fn push_subterm(&mut self, lvl: Level, term: &'a Term) {
-        self.state_stack.push(IteratorState::to_state(lvl, term));
-    }
-
-    fn new(term: &'a Term) -> QueryIterator<'a> {
-        let state = match term {
-            &Term::Atom(ref cell, ref atom) =>
-                IteratorState::IsolatedAtom(cell, atom),
-            &Term::Clause(_, _, ref terms) =>
-                IteratorState::RootClause(0, terms),
-            &Term::Var(ref cell, ref var) =>
-                IteratorState::IsolatedVar(cell, var)
-        };
-        
-        QueryIterator { state_stack: vec![state] }
-    }
-}
-
-impl<'a> Iterator for QueryIterator<'a> {
-    type Item = TermRef<'a>;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        while let Some(iter_state) = self.state_stack.pop() {
-            match iter_state {
-                IteratorState::Atom(lvl, cell, atom) =>
-                    return Some(TermRef::Atom(lvl, cell, atom)),
-                IteratorState::Clause(lvl, child_num, cell, atom, child_terms) => {
-                    if child_num == child_terms.len() {
-                        return Some(TermRef::Clause(lvl, cell, atom, child_terms));
-                    } else {
-                        self.push_clause(lvl, child_num + 1, cell, atom, child_terms);
-                        self.push_subterm(Level::Deep, child_terms[child_num].as_ref());
-                    }
-                },
-                IteratorState::IsolatedAtom(cell, atom) =>
-                    return Some(TermRef::Atom(Level::Shallow, cell, atom)),
-                IteratorState::IsolatedVar(cell, var) =>
-                    return Some(TermRef::Var(Level::Shallow, cell, var)),
-                IteratorState::RootClause(child_num, child_terms) => {
-                    if child_num == child_terms.len() {
-                        return None;
-                    } else {
-                        self.push_root_clause(child_num + 1, child_terms);
-                        self.push_subterm(Level::Shallow, child_terms[child_num].as_ref());
-                    }
-                },
-                IteratorState::Var(lvl, cell, var) =>
-                    return Some(TermRef::Var(lvl, cell, var))
-            };
-        }
-
-        None
-    }
-}
-
-pub struct FactIterator<'a> {
-    state_queue: VecDeque<IteratorState<'a>>,
-}
-
-impl<'a> FactIterator<'a> {
-    fn push_subterm(&mut self, lvl: Level, term: &'a Term) {
-        self.state_queue.push_back(IteratorState::to_state(lvl, term));
-    }
-
-    fn new(term: &'a Term) -> FactIterator<'a> {
-        let states = match term {
-            &Term::Atom(ref cell, ref atom) =>
-                vec![IteratorState::IsolatedAtom(cell, atom)],
-            &Term::Clause(_, _, ref terms) =>
-                vec![IteratorState::RootClause(0, terms)],
-            &Term::Var(ref cell, ref var) =>
-                vec![IteratorState::IsolatedVar(cell, var)]
-        };
-
-        FactIterator { state_queue:  VecDeque::from(states) }
-    }
-}
-
-impl<'a> Iterator for FactIterator<'a> {
-    type Item = TermRef<'a>;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        while let Some(state) = self.state_queue.pop_front() {
-            match state {
-                IteratorState::Atom(lvl, cell, atom) =>
-                    return Some(TermRef::Atom(lvl, cell, atom)),
-                IteratorState::Clause(lvl, _, cell, atom, child_terms) => {
-                    for child_term in child_terms {
-                        self.push_subterm(Level::Deep, child_term);
-                    }
-
-                    return Some(TermRef::Clause(lvl, cell, atom, child_terms));
-                },
-                IteratorState::IsolatedAtom(cell, atom) =>
-                    return Some(TermRef::Atom(Level::Shallow, cell, atom)),
-                IteratorState::IsolatedVar(cell, var) =>
-                    return Some(TermRef::Var(Level::Shallow, cell, var)),
-                IteratorState::RootClause(_, child_terms) => {
-                    for child_term in child_terms {
-                        self.push_subterm(Level::Shallow, child_term);
-                    }
-                },
-                IteratorState::Var(lvl, cell, var) =>
-                    return Some(TermRef::Var(lvl, cell, var))
-            }
-        }
-
-        None
-    }
-}
-
-impl Term {
-    pub fn post_order_iter(&self) -> QueryIterator {
-        QueryIterator::new(self)
-    }
-
-    pub fn breadth_first_iter(&self) -> FactIterator {
-        FactIterator::new(self)
-    }
-}

src/l1/l1_parser.lalrpop

@@ -1,32 +0,0 @@
-use std::cell::Cell;
-
-use l1::ast::{Atom, Reg, Term, TopLevel, Var};
-
-grammar;
-
-pub TopLevel: TopLevel = {
-    "?-" <t:Term> "." => TopLevel::Query(t),
-    <t:Term> "."      => TopLevel::Fact(t),
-};
-
-Atom : Atom = {
-    r"[a-z][a-z0-9_]*" => <>.trim().to_string(),
-};
-
-Var : Var = {
-    r"[A-Z][a-z0-9_]*" => <>.trim().to_string(),
-};
-
-BoxedTerm : Box<Term> = {
-    <t:Term> => Box::new(t),
-};
-
-Term : Term = {
-    <a:Atom> "(" <ts: (<BoxedTerm> ",")*> <t:BoxedTerm> ")" => {
-     	let mut ts = ts;
-     	ts.push(t);
-	Term::Clause(Cell::new(0), a, ts)
-    },
-    <Atom> => Term::Atom(Cell::new(0), <>),
-    <Var>  => Term::Var(Cell::new(Reg::Norm(0)), <>)
-};

src/l1/machine.rs

@@ -1,309 +0,0 @@
-use l1::ast::{Addr, Atom, CompiledFact, CompiledQuery,
-              FactInstruction, Heap, HeapCellValue, QueryInstruction,
-              Registers};
-
-use std::collections::HashMap;
-use std::vec::Vec;
-
-#[derive(Clone, Copy)]
-enum MachineMode {
-    Read,
-    Write
-}
-
-pub struct Machine {
-    h : usize,
-    s : usize,
-    p : usize,
-    code : CompiledFact,
-    code_dir : HashMap<(Atom, usize), usize>,
-    fail : bool,
-    heap : Heap,
-    mode : MachineMode,
-    registers : Registers
-}
-
-impl Machine {
-    pub fn new() -> Machine {
-        Machine { h : 0,
-                  s : 0,
-                  p : 0,
-                  code : Vec::new(),
-                  code_dir : HashMap::new(),
-                  fail : false,
-                  heap : Vec::with_capacity(256),
-                  mode : MachineMode::Write,
-                  registers : vec![HeapCellValue::Ref(0); 32] }
-    }
-
-    pub fn add_fact(&mut self, mut fact: CompiledFact, name: Atom, arity: usize)
-    {
-        let index = self.code.len();
-
-        self.code.append(&mut fact);
-        self.code_dir.insert((name, arity), index);
-    }
-
-    pub fn failed(&self) -> bool {
-        self.fail
-    }
-
-    fn lookup(&self, a: Addr) -> &HeapCellValue {
-        match a {
-            Addr::HeapCell(hc) => &self.heap[hc],
-            Addr::RegNum(reg)  => &self.registers[reg]
-        }
-    }
-
-    fn deref(&self, a: Addr) -> Addr {
-        let mut a = a;
-
-        loop {
-            if let &HeapCellValue::Ref(value) = self.lookup(a) {
-                if let Addr::HeapCell(av) = a {
-                    if value != av {
-                        a = Addr::HeapCell(value);
-                        continue;
-                    }
-                } else {
-                    a = Addr::HeapCell(value);
-                    continue;
-                }
-            }
-
-            return a;
-        };
-    }
-
-    fn is_unbound(hc: &HeapCellValue, index: usize) -> bool {
-        match hc {
-            &HeapCellValue::Ref(r) => r == index,
-            _ => false
-        }
-    }
-
-    //TODO: try to compress this function.
-    fn bind(&mut self, a: Addr, val: usize) {
-        let mut a = a;
-
-        loop {
-            match a {
-                Addr::RegNum(reg) => {
-                    if let HeapCellValue::Ref(hc) = self.registers[reg] {
-                        a = Addr::HeapCell(hc);
-                    } else if Machine::is_unbound(&self.heap[val], val) {
-                        self.heap[val] = self.registers[reg].clone();
-                        break;
-                    } else {
-                        self.fail = true;
-                        break;
-                    }
-                },
-                Addr::HeapCell(hc) if Machine::is_unbound(&self.heap[hc], hc) => {
-                    self.heap[hc] = HeapCellValue::Ref(val);
-                    break;
-                },
-                Addr::HeapCell(hc) if Machine::is_unbound(&self.heap[val], val) => {
-                    self.heap[val] = HeapCellValue::Ref(hc);
-                    break;
-                },
-                _ => {
-                    self.fail = true;
-                    break;
-                }
-            };
-        }
-    }
-
-    fn unify(&mut self, a1: Addr, a2: Addr) {
-        let mut pdl = vec![a1, a2];
-
-        self.fail = false;
-
-        while !(pdl.is_empty() || self.fail) {
-            let d1 = self.deref(pdl.pop().unwrap());
-            let d2 = self.deref(pdl.pop().unwrap());
-
-            if d1 != d2 {
-                match (self.lookup(d1), self.lookup(d2)) {
-                    (&HeapCellValue::Ref(hc), _) =>
-                        self.bind(d2, hc),
-                    (_, &HeapCellValue::Ref(hc)) =>
-                        self.bind(d1, hc),
-                    (&HeapCellValue::Str(a1), &HeapCellValue::Str(a2)) => {
-                        let r1 = &self.heap[a1];
-                        let r2 = &self.heap[a2];
-
-                        if let &HeapCellValue::NamedStr(n1, ref f1) = r1 {
-                            if let &HeapCellValue::NamedStr(n2, ref f2) = r2 {
-                                if n1 == n2 && *f1 == *f2 {
-                                    for i in 1 .. n1 {
-                                        pdl.push(Addr::HeapCell(a1 + i));
-                                        pdl.push(Addr::HeapCell(a2 + i));
-                                    }
-
-                                    continue;
-                                }
-                            }
-                        }
-
-                        self.fail = true;
-                    },
-                    _ => self.fail = true,
-                };
-            }
-        }
-    }
-
-    pub fn execute_fact(&mut self) {
-        loop {
-            if let &FactInstruction::Proceed = &self.code[self.p] {
-                break;
-            } else if self.fail {
-                break;
-            }
-
-            let fact_instr = self.code[self.p].clone();
-            self.execute_fact_instr(fact_instr);
-        }
-    }
-
-    pub fn execute_query(&mut self, query: &CompiledQuery) {
-        for instr in query {
-            self.execute_query_instr(instr);
-
-            if self.fail {
-                break;
-            }
-        }
-    }
-
-    fn execute_query_instr<'a, 'b: 'a>(&'a mut self, instr: &'b QueryInstruction) {
-        match instr {
-            &QueryInstruction::Call(ref name, arity) => {
-                // why is Option<&T> not Deref?!?!?
-                // is it because if the value is None, there's nothing to
-                // dereference?
-                let compiled_fact_index =
-                    self.code_dir.get(&(name.clone(), arity))
-                        .map(|index| *index);
-
-                match compiled_fact_index {
-                    Some(compiled_fact_index) => {
-                        self.p = compiled_fact_index;
-                        self.execute_fact();
-                    },
-                    None => self.fail = true,
-                };
-            }
-            &QueryInstruction::PutStructure(_, ref name, arity, reg) => {
-                self.heap.push(HeapCellValue::Str(self.h + 1));
-                self.heap.push(HeapCellValue::NamedStr(arity, name.clone()));
-
-                self.registers[reg] = self.heap[self.h].clone();
-
-                self.h += 2;
-            },
-            &QueryInstruction::PutValue(arg, norm) =>
-                self.registers[arg] = self.registers[norm].clone(),
-            &QueryInstruction::PutVariable(arg, norm) => {
-                self.heap.push(HeapCellValue::Ref(self.h));
-
-                self.registers[norm] = self.heap[self.h].clone();
-                self.registers[arg]  = self.heap[self.h].clone();
-
-                self.h += 1;
-            },
-            &QueryInstruction::SetVariable(reg) => {
-                self.heap.push(HeapCellValue::Ref(self.h));
-                self.registers[reg] = self.heap[self.h].clone();
-
-                self.h += 1;
-            },
-            &QueryInstruction::SetValue(reg) => {
-                self.heap.push(self.registers[reg].clone());
-                self.h += 1;
-            },
-        }
-    }
-
-    fn execute_fact_instr(&mut self, instr: FactInstruction) {
-        match instr {
-            FactInstruction::Proceed => return,
-            FactInstruction::GetStructure(_, name, arity, reg) => {
-                let addr = self.deref(Addr::RegNum(reg));
-
-                match self.lookup(addr) {
-                    &HeapCellValue::Str(a) => {
-                        let result = &self.heap[a];
-
-                        if let &HeapCellValue::NamedStr(named_arity, ref named_str) = result {
-                            if arity == named_arity && *name == *named_str {
-                                self.s = a + 1;
-                                self.mode = MachineMode::Read;
-                            } else {
-                                self.fail = true;
-                            }
-                        }
-                    },
-                    &HeapCellValue::Ref(r) => {
-                        self.heap.push(HeapCellValue::Str(self.h + 1));
-                        self.heap.push(HeapCellValue::NamedStr(arity, name));
-
-                        let h = self.h;
-
-                        self.bind(Addr::HeapCell(r), h);
-
-                        self.h += 2;
-                        self.mode = MachineMode::Write;
-                    },
-                    _ => {
-                        self.fail = true;
-                    }
-                };
-            },
-            FactInstruction::GetVariable(arg, norm) =>
-                self.registers[norm] = self.registers[arg].clone(),
-            FactInstruction::GetValue(arg, norm) =>
-                self.unify(Addr::RegNum(norm), Addr::RegNum(arg)),
-            FactInstruction::UnifyVariable(reg) => {
-                match self.mode {
-                    MachineMode::Read  => self.registers[reg] = self.heap[self.s].clone(),
-                    MachineMode::Write => {
-                        self.heap.push(HeapCellValue::Ref(self.h));
-                        self.registers[reg] = self.heap[self.h].clone();
-                        self.h += 1;
-                    }
-                };
-
-                self.s += 1;
-            },
-            FactInstruction::UnifyValue(reg) => {
-                let s = self.s;
-
-                match self.mode {
-                    MachineMode::Read  => self.unify(Addr::RegNum(reg), Addr::HeapCell(s)),
-                    MachineMode::Write => {
-                        self.heap.push(self.registers[reg].clone());
-                        self.h += 1;
-                    }
-                };
-
-                self.s += 1;
-            }
-        }
-
-        self.p += 1;
-    }
-
-    pub fn reset_machine_state(&mut self) {
-        self.h = 0;
-        self.s = 0;
-        self.p = 0;
-
-        self.fail = false;
-        self.heap = Vec::with_capacity(256);
-        self.mode = MachineMode::Write;
-        self.registers = vec![HeapCellValue::Ref(0); 32];
-    }
-}

src/l1/mod.rs

@@ -1,5 +0,0 @@
-pub mod ast;
-pub mod iterators;
-pub mod l1_parser;
-pub mod codegen;
-pub mod machine;

src/l2/ast.rs

@@ -1,253 +0,0 @@
-use std::cell::Cell;
-use std::fmt;
-use std::ops::{Add, AddAssign};
-use std::vec::Vec;
-
-pub type Var = String;
-
-pub type Atom = String;
-
-pub enum TopLevel {
-    Fact(Term),
-    Rule(Rule),
-    Query(Term)
-}
-
-#[derive(Clone, Copy)]
-pub enum Level {
-    Shallow, Deep
-}
-
-impl fmt::Display for Level {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self {
-            &Level::Shallow => write!(f, "A"),
-            &Level::Deep => write!(f, "X")
-        }
-    }
-}
-
-#[derive(Clone, Copy)]
-pub enum RegType {
-    Perm(usize),
-    Temp(usize)
-}
-
-impl RegType {
-    pub fn reg_num(self) -> usize {
-        match self {
-            RegType::Perm(reg_num) | RegType::Temp(reg_num) => reg_num
-        }
-    }
-
-    pub fn is_perm(self) -> bool {
-        match self {
-            RegType::Perm(_) => true,
-            _ => false
-        }
-    }
-}
-
-impl fmt::Display for VarReg {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self {
-            &VarReg::Norm(RegType::Perm(reg)) => write!(f, "Y{}", reg),
-            &VarReg::Norm(RegType::Temp(reg)) => write!(f, "X{}", reg),
-            &VarReg::ArgAndNorm(RegType::Perm(reg), arg) =>
-                write!(f, "Y{} A{}", reg, arg),
-            &VarReg::ArgAndNorm(RegType::Temp(reg), arg) =>
-                write!(f, "X{} A{}", reg, arg)
-        }
-    }
-}
-
-impl From<RegType> for Addr {
-    fn from(reg: RegType) -> Addr {
-        match reg {
-            RegType::Perm(reg) => Addr::StackCell(reg),
-            RegType::Temp(reg) => Addr::RegNum(reg)
-        }
-    }
-}
-
-impl fmt::Display for RegType {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self {
-            &RegType::Perm(val) => write!(f, "Y{}", val),
-            &RegType::Temp(val) => write!(f, "X{}", val)
-        }
-    }
-}
-
-#[derive(Clone, Copy)]
-pub enum VarReg {
-    ArgAndNorm(RegType, usize),
-    Norm(RegType)
-}
-
-impl VarReg {
-    pub fn norm(self) -> RegType {
-        match self {
-            VarReg::ArgAndNorm(reg, _) | VarReg::Norm(reg) => reg
-        }
-    }
-
-    pub fn root_register(self) -> usize {
-        match self {
-            VarReg::ArgAndNorm(_, root) => root,
-            VarReg::Norm(root) => root.reg_num()
-        }
-    }
-}
-
-pub enum Term {
-    Atom(Cell<RegType>, Atom),
-    Clause(Cell<RegType>, Atom, Vec<Box<Term>>),
-    Var(Cell<VarReg>, Var)
-}
-
-pub struct Rule {
-    pub head: (Term, Term),
-    pub clauses: Vec<Term>
-}
-
-pub enum TermRef<'a> {
-    Atom(Level, &'a Cell<RegType>, &'a Atom),
-    Clause(Level, &'a Cell<RegType>, &'a Atom, &'a Vec<Box<Term>>),
-    Var(Level, &'a Cell<VarReg>, &'a Var)
-}
-
-pub enum FactInstruction {
-    GetStructure(Level, Atom, usize, RegType),
-    GetValue(RegType, usize),
-    GetVariable(RegType, usize),
-    UnifyVariable(RegType),
-    UnifyValue(RegType)
-}
-
-pub enum QueryInstruction {
-    PutStructure(Level, Atom, usize, RegType),
-    PutValue(RegType, usize),
-    PutVariable(RegType, usize),
-    SetVariable(RegType),
-    SetValue(RegType)
-}
-
-pub enum ControlInstruction {
-    Allocate(usize),
-    Call(Atom, usize),
-    Deallocate,
-    Proceed
-}
-
-pub type CompiledFact = Vec<FactInstruction>;
-
-pub type CompiledQuery = Vec<QueryInstruction>;
-
-pub enum Line {
-    Control(ControlInstruction),    
-    Fact(CompiledFact),
-    Query(CompiledQuery)
-}
-
-pub type Code = Vec<Line>;
-
-#[derive(Clone, Copy, PartialEq)]
-pub enum Addr {
-    HeapCell(usize),
-    RegNum(usize),
-    StackCell(usize),
-}
-
-#[derive(Clone, PartialEq)]
-pub enum HeapCellValue {
-    NamedStr(usize, Atom),
-    Ref(usize),
-    Str(usize)
-}
-
-impl HeapCellValue {
-    pub fn as_ref(&self, focus: usize) -> HeapCellRef {
-        match self {
-            &HeapCellValue::Ref(r) => HeapCellRef::Ref(r),
-            &HeapCellValue::Str(s) => HeapCellRef::Str(s),
-            &HeapCellValue::NamedStr(_, _) => HeapCellRef::Str(focus)
-        }
-    }
-}
-
-#[derive(Copy, Clone)]
-pub enum HeapCellRef {
-    Ref(usize),
-    Str(usize)
-}
-
-impl HeapCellRef {
-    pub fn heap_offset(&self) -> usize {
-        match self {
-            &HeapCellRef::Ref(r) | &HeapCellRef::Str(r) => r
-        }
-    }        
-}
-
-impl From<HeapCellRef> for HeapCellValue {
-    fn from(hcr: HeapCellRef) -> HeapCellValue {
-        match hcr {
-            HeapCellRef::Ref(r) => HeapCellValue::Ref(r),
-            HeapCellRef::Str(s) => HeapCellValue::Str(s)
-        }
-    }
-}
-
-#[derive(Clone, Copy)]
-pub enum CodePtr {
-    DirEntry(usize),
-    TopLevel
-}
-
-impl Add<usize> for CodePtr {
-    type Output = CodePtr;
-    fn add(self, rhs: usize) -> Self::Output {
-        match self {
-            CodePtr::DirEntry(p) => CodePtr::DirEntry(p + rhs),
-            CodePtr::TopLevel => CodePtr::TopLevel
-        }
-    }
-}
-
-impl AddAssign<usize> for CodePtr {
-    fn add_assign(&mut self, rhs: usize) {
-        match self {
-            &mut CodePtr::DirEntry(ref mut p) => *p += rhs,
-            _ => {}
-        }
-    }
-}
-
-pub type Heap = Vec<HeapCellValue>;
-
-pub type Registers = Vec<HeapCellRef>;
-
-impl Term {
-    pub fn subterms(&self) -> usize {
-        match self {
-            &Term::Clause(_, _, ref terms) => terms.len(),
-            _ => 1
-        }
-    }
-
-    pub fn name(&self) -> &Atom {
-        match self {
-            &Term::Atom(_, ref atom)
-            | &Term::Var(_, ref atom)
-            | &Term::Clause(_, ref atom, _) => atom
-        }
-    }
-
-    pub fn arity(&self) -> usize {
-        match self {
-            &Term::Atom(_, _) | &Term::Var(_, _) => 0,
-            &Term::Clause(_, _, ref child_terms) => child_terms.len()
-        }
-    }
-}

src/l2/codegen.rs

@@ -1,469 +0,0 @@
-use l2::ast::*;
-use l2::iterators::{FactIterator, QueryIterator};
-
-use std::cell::Cell;
-use std::cmp::max;
-use std::collections::HashMap;
-use std::fmt;
-use std::vec::Vec;
-
-impl fmt::Display for FactInstruction {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self {
-            &FactInstruction::GetStructure(Level::Deep, ref name, ref arity, ref r) =>
-                write!(f, "get_structure {}/{}, {}", name, arity, r),
-            &FactInstruction::GetStructure(Level::Shallow, ref name, ref arity, ref r) =>
-                write!(f, "get_structure {}/{}, A{}", name, arity, r.reg_num()),
-            &FactInstruction::GetValue(ref x, ref a) =>
-                write!(f, "get_value {}, A{}", x, a),
-            &FactInstruction::GetVariable(ref x, ref a) =>
-                write!(f, "get_variable {}, A{}", x, a),
-            &FactInstruction::UnifyVariable(ref r) =>
-                write!(f, "unify_variable {}", r),
-            &FactInstruction::UnifyValue(ref r) =>
-                write!(f, "unify_value {}", r)
-        }
-    }
-}
-
-impl fmt::Display for QueryInstruction {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self {
-            &QueryInstruction::PutStructure(Level::Deep, ref name, ref arity, ref r) =>
-                write!(f, "put_structure {}/{}, A{}", name, arity, r.reg_num()),
-            &QueryInstruction::PutStructure(Level::Shallow, ref name, ref arity, ref r) =>
-                write!(f, "put_structure {}/{}, {}", name, arity, r),
-            &QueryInstruction::PutValue(ref x, ref a) =>
-                write!(f, "put_value {}, A{}", x, a),
-            &QueryInstruction::PutVariable(ref x, ref a) =>
-                write!(f, "put_variable {}, A{}", x, a),
-            &QueryInstruction::SetVariable(ref r) =>
-                write!(f, "set_variable {}", r),
-            &QueryInstruction::SetValue(ref r) =>
-                write!(f, "set_value {}", r),
-        }
-    }
-}
-
-impl fmt::Display for ControlInstruction {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self {
-            &ControlInstruction::Allocate(num_cells) =>
-                write!(f, "allocate {}", num_cells),
-            &ControlInstruction::Call(ref name, ref arity) =>
-                write!(f, "call {}/{}", name, arity),
-            &ControlInstruction::Deallocate =>
-                write!(f, "deallocate"),
-            &ControlInstruction::Proceed =>
-                write!(f, "proceed")
-        }
-    }
-}
-
-trait CompilationTarget<'a> {
-    type Iterator : Iterator<Item=TermRef<'a>>;
-
-    fn iter(&'a Term) -> Self::Iterator;
-
-    fn to_structure(Level, Atom, usize, RegType) -> Self;
-
-    fn argument_to_variable(RegType, usize) -> Self;
-    fn argument_to_value(RegType, usize) -> Self;
-    fn subterm_to_variable(RegType) -> Self;
-    fn subterm_to_value(RegType) -> Self;
-
-    fn clause_arg_to_instr(RegType) -> Self;
-}
-
-impl<'a> CompilationTarget<'a> for FactInstruction {
-    type Iterator = FactIterator<'a>;
-
-    fn iter(term: &'a Term) -> Self::Iterator {
-        term.breadth_first_iter()
-    }
-
-    fn to_structure(lvl: Level, atom: Atom, arity: usize, reg: RegType) -> Self {
-        FactInstruction::GetStructure(lvl, atom, arity, reg)
-    }
-
-    fn argument_to_variable(arg: RegType, val: usize) -> Self {
-        FactInstruction::GetVariable(arg, val)
-    }
-
-    fn argument_to_value(arg: RegType, val: usize) -> Self {
-        FactInstruction::GetValue(arg, val)
-    }
-
-    fn subterm_to_variable(val: RegType) -> Self {
-        FactInstruction::UnifyVariable(val)
-    }
-
-    fn subterm_to_value(val: RegType) -> Self {
-        FactInstruction::UnifyValue(val)
-    }
-
-    fn clause_arg_to_instr(val: RegType) -> Self {
-        FactInstruction::UnifyVariable(val)
-    }
-}
-
-impl<'a> CompilationTarget<'a> for QueryInstruction {
-    type Iterator = QueryIterator<'a>;
-
-    fn iter(term: &'a Term) -> Self::Iterator {
-        term.post_order_iter()
-    }
-
-    fn to_structure(lvl: Level, atom: Atom, arity: usize, reg: RegType) -> Self {
-        QueryInstruction::PutStructure(lvl, atom, arity, reg)
-    }
-
-    fn argument_to_variable(arg: RegType, val: usize) -> Self {
-        QueryInstruction::PutVariable(arg, val)
-    }
-
-    fn argument_to_value(arg: RegType, val: usize) -> Self {
-        QueryInstruction::PutValue(arg, val)
-    }
-
-    fn subterm_to_variable(val: RegType) -> Self {
-        QueryInstruction::SetVariable(val)
-    }
-
-    fn subterm_to_value(val: RegType) -> Self {
-        QueryInstruction::SetValue(val)
-    }
-
-    fn clause_arg_to_instr(val: RegType) -> Self {
-        QueryInstruction::SetValue(val)
-    }
-}
-
-struct TermMarker<'a> {
-    bindings: HashMap<&'a Var, VarReg>,
-    arg_c:    usize,
-    perm_c:   usize,
-    temp_c:   usize
-}
-
-impl<'a> TermMarker<'a> {
-    fn new() -> TermMarker<'a> {
-        TermMarker { bindings: HashMap::new(),
-                     arg_c:    1,
-                     perm_c:   1,
-                     temp_c:   1 }
-    }
-
-    fn contains_var(&self, var: &'a Var) -> bool {
-        self.bindings.contains_key(var)
-    }
-
-    fn get(&self, var: &'a Var) -> VarReg {
-        *self.bindings.get(var).unwrap()
-    }
-
-    fn insert(&mut self, var: &'a Var, r: VarReg) {
-        self.bindings.insert(var, r);
-    }
-
-    fn mark_non_var(&mut self, lvl: Level, cell: &Cell<RegType>) {
-        let reg_type = cell.get();
-
-        if reg_type.reg_num() == 0 {
-            match lvl {
-                Level::Deep if reg_type.is_perm() => {
-                    let perm = self.perm_c;
-                    self.perm_c += 1;
-                    cell.set(RegType::Perm(perm));
-                },
-                Level::Deep => {
-                    let temp = self.temp_c;
-                    self.temp_c += 1;
-                    cell.set(RegType::Temp(temp));
-                },
-                Level::Shallow if reg_type.is_perm() => {
-                    let arg = self.arg_c;
-                    self.arg_c += 1;
-                    cell.set(RegType::Perm(arg));
-                },
-                Level::Shallow => {
-                    let arg = self.arg_c;
-                    self.arg_c += 1;
-                    cell.set(RegType::Temp(arg));
-                }
-            };
-        }
-    }
-
-    fn mark_old_var(&mut self, lvl: Level, var: &'a Var) -> VarReg
-    {
-        let reg = self.get(var);
-
-        match lvl {
-            Level::Deep => VarReg::Norm(reg.norm()),
-            Level::Shallow => {
-                let reg = VarReg::ArgAndNorm(reg.norm(), self.arg_c);
-
-                self.arg_c += 1;
-                self.insert(var, reg);
-
-                reg
-            }
-        }
-    }
-
-    fn mark_new_var(&mut self, lvl: Level, var: &'a Var, reg: RegType) -> VarReg
-    {
-        let inner_reg = if reg.is_perm() {
-            let perm = self.perm_c;
-            self.perm_c += 1;
-            RegType::Perm(perm)
-        } else {
-            let temp = self.temp_c;
-            self.temp_c += 1;
-            RegType::Temp(temp)
-        };
-
-        let reg = match lvl {
-            Level::Deep => VarReg::Norm(inner_reg),
-            Level::Shallow => {
-                let reg = VarReg::ArgAndNorm(inner_reg, self.arg_c);
-                self.arg_c += 1;
-                reg
-            }
-        };
-
-        self.insert(var, reg);
-        reg
-    }
-
-    fn advance_at_header(&mut self, term: &'a Term) {
-        self.arg_c = 1;
-        self.temp_c = max(term.subterms(), self.temp_c) + 1;
-    }
-
-    fn advance(&mut self, term: &'a Term) {
-        self.arg_c = 1;
-        self.temp_c = term.subterms() + 1;
-    }
-}
-
-#[derive(Copy, Clone)]
-enum TermStatus {
-    New, Old, Recurrent
-}
-
-pub struct CodeGenerator<'a> {
-    marker: TermMarker<'a>
-}
-
-type VariableFixture<'a>  = (TermStatus, Vec<&'a Cell<VarReg>>);
-type VariableFixtures<'a> = HashMap<&'a Var, VariableFixture<'a>>;
-
-impl<'a> CodeGenerator<'a> {
-    pub fn new() -> Self {
-        CodeGenerator { marker: TermMarker::new() }
-    }
-
-    pub fn vars(&self) -> &HashMap<&Var, VarReg> {
-        &self.marker.bindings
-    }
-
-    fn to_structure<Target>(&mut self,
-                            lvl: Level,
-                            name: &'a Atom,
-                            cell: &'a Cell<RegType>,
-                            arity: usize)
-                            -> Target
-        where Target: CompilationTarget<'a>
-    {
-        self.marker.mark_non_var(lvl, cell);
-        Target::to_structure(lvl, name.clone(), arity, cell.get())
-    }
-
-    fn var_term<Target>(&mut self,
-                        lvl: Level,
-                        cell: &'a Cell<VarReg>,
-                        var: &'a Var)
-                        -> Target
-        where Target: CompilationTarget<'a>
-    {
-        if !self.marker.contains_var(var) {
-            let reg = self.marker.mark_new_var(lvl, var, cell.get().norm());
-            cell.set(reg);
-
-            match reg {
-                VarReg::ArgAndNorm(arg, norm) =>
-                    Target::argument_to_variable(arg, norm),
-                VarReg::Norm(norm) =>
-                    Target::subterm_to_variable(norm)
-            }
-        } else {
-            let reg = self.marker.mark_old_var(lvl, var);
-            cell.set(reg);
-
-            match reg {
-                VarReg::ArgAndNorm(arg, norm) =>
-                    Target::argument_to_value(arg, norm),
-                VarReg::Norm(norm) =>
-                    Target::subterm_to_value(norm)
-            }
-        }
-    }
-
-    fn non_var_subterm<Target>(&mut self, cell: &'a Cell<RegType>) -> Target
-        where Target: CompilationTarget<'a>
-    {
-        self.marker.mark_non_var(Level::Deep, cell);
-        Target::clause_arg_to_instr(cell.get())
-    }
-
-    fn subterm_to_instr<Target>(&mut self, subterm: &'a Term) -> Target
-        where Target: CompilationTarget<'a>
-    {
-        match subterm {
-            &Term::Atom(ref cell, _) | &Term::Clause(ref cell, _, _) =>
-                self.non_var_subterm(cell),
-            &Term::Var(ref cell, ref var) =>
-                self.var_term(Level::Deep, cell, var)
-        }
-    }
-
-    fn compile_target<Target>(&mut self, term: &'a Term) -> Vec<Target>
-        where Target: CompilationTarget<'a>
-    {
-        let iter       = Target::iter(term);
-        let mut target = Vec::new();
-
-        for term in iter {
-            match term {
-                TermRef::Atom(lvl, term, atom) =>
-                    target.push(self.to_structure(lvl, atom, term, 0)),
-                TermRef::Clause(lvl, term, atom, terms) => {
-                    target.push(self.to_structure(lvl, atom, term, terms.len()));
-
-                    for subterm in terms {
-                        target.push(self.subterm_to_instr(subterm.as_ref()));
-                    }
-                },
-                TermRef::Var(lvl @ Level::Shallow, ref cell, ref var) =>
-                    target.push(self.var_term(lvl, cell, var)),
-                _ => {}
-            };
-        }
-
-        target
-    }
-
-    fn mark_vars_in_term<Iter>(iter: Iter, vs: &mut VariableFixtures<'a>)
-        where Iter : Iterator<Item=TermRef<'a>>
-    {
-        for term in iter {
-            if let TermRef::Var(_, reg_cell, var) = term {
-                let mut status = vs.entry(var)
-                                   .or_insert((TermStatus::New, Vec::new()));
-
-                status.1.push(reg_cell);
-
-                match status.0 {
-                    TermStatus::Old => status.0 = TermStatus::Recurrent,
-                    _ => {}
-                };
-            }
-        }
-
-        for &mut (ref mut term_status, ref mut cb) in vs.values_mut() {
-            match *term_status {
-                TermStatus::New => *term_status = TermStatus::Old,
-                TermStatus::Recurrent => {
-                    for cell_reg in cb.drain(0..) {
-                        cell_reg.set(VarReg::Norm(RegType::Perm(0)));
-                    }
-                },
-                _ => {}
-            }
-        }
-    }
-
-    fn mark_perm_vars(rule: &'a Rule) -> VariableFixtures {
-        let &Rule { head: (ref p0, ref p1), ref clauses } = rule;
-        let mut vfs = HashMap::new();
-
-        let iter = p0.breadth_first_iter().chain(p1.breadth_first_iter());
-
-        Self::mark_vars_in_term(iter, &mut vfs);
-
-        for term in clauses {
-            Self::mark_vars_in_term(term.breadth_first_iter(), &mut vfs);
-        }
-
-        vfs
-    }
-
-    fn add_conditional_call(compiled_query: &mut Code, term: &Term) {
-        match term {
-            &Term::Atom(_, ref atom) => {
-                let call = ControlInstruction::Call(atom.clone(), 0);
-                compiled_query.push(Line::Control(call));
-            },
-            &Term::Clause(_, ref atom, ref terms) => {
-                let call = ControlInstruction::Call(atom.clone(), terms.len());
-                compiled_query.push(Line::Control(call));
-            },
-            _ => {}
-        }
-    }
-
-    pub fn compile_rule(&mut self, rule: &'a Rule) -> Code {
-        let vfs = Self::mark_perm_vars(&rule);
-        let &Rule { head: (ref p0, ref p1), ref clauses } = rule;
-        let mut perm_vars = 0;
-
-        for &(term_status, _) in vfs.values() {
-            if let TermStatus::Recurrent = term_status {
-                perm_vars += 1;
-            }
-        }
-
-        let mut body = Vec::new();
-
-        body.push(Line::Control(ControlInstruction::Allocate(perm_vars)));
-
-        self.marker.advance(p0);
-        body.push(Line::Fact(self.compile_target(p0)));
-
-        self.marker.advance_at_header(p1);
-        body.push(Line::Query(self.compile_target(p1)));
-        Self::add_conditional_call(&mut body, p1);
-
-        body = clauses.iter()
-            .map(|ref term| self.compile_query(term))
-            .fold(body, |mut body, ref mut cqs| {
-                body.append(cqs);
-                body
-            });
-
-        body.push(Line::Control(ControlInstruction::Deallocate));
-
-        body
-    }
-
-    pub fn compile_fact(&mut self, term: &'a Term) -> Code {
-        self.marker.advance(term);
-
-        let mut compiled_fact = vec![Line::Fact(self.compile_target(term))];
-        let proceed = Line::Control(ControlInstruction::Proceed);
-
-        compiled_fact.push(proceed);
-        compiled_fact
-    }
-
-    pub fn compile_query(&mut self, term: &'a Term) -> Code {
-        self.marker.advance(term);
-
-        let mut compiled_query = vec![Line::Query(self.compile_target(term))];
-        Self::add_conditional_call(&mut compiled_query, term);
-
-        compiled_query
-    }
-}

src/l2/heapview.rs

@@ -1,64 +0,0 @@
-use l2::ast::*;
-
-use std::vec::Vec;
-
-#[derive(Clone, Copy)]
-pub enum HeapCellView<'a> {
-    Str(usize, &'a Atom),
-    Var(usize)
-}
-
-pub struct HeapCellViewer<'a> {
-    heap: &'a Heap,
-    state_stack: Vec<(usize, &'a HeapCellValue)>
-}
-
-impl<'a> HeapCellViewer<'a> {
-    pub fn new(heap: &'a Heap, focus: usize) -> Self {
-        HeapCellViewer {
-            heap: heap,
-            state_stack: vec![(focus, &heap[focus])]
-        }
-    }
-
-    fn follow(&self, value: &'a HeapCellValue) -> &'a HeapCellValue {
-        match value {
-            &HeapCellValue::NamedStr(_, _) => value,
-            &HeapCellValue::Ref(cell_num) | &HeapCellValue::Str(cell_num) =>
-                &self.heap[cell_num],
-        }
-    }
-}
-
-impl<'a> Iterator for HeapCellViewer<'a> {
-    type Item = HeapCellView<'a>;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        while let Some(hcv) = self.state_stack.pop() {
-            match hcv {
-                (focus, &HeapCellValue::NamedStr(arity, ref name)) => {
-                    for i in (1 .. arity + 1).rev() {
-                        self.state_stack.push((focus + i, &self.heap[focus + i]));
-                    }                            
-                    
-                    return Some(HeapCellView::Str(arity, name));
-                },
-                (_, &HeapCellValue::Ref(cell_num)) => {
-                    let new_hcv = self.follow(hcv.1);
-
-                    if hcv.1 == new_hcv {
-                        return Some(HeapCellView::Var(cell_num));
-                    } else {
-                        self.state_stack.push((cell_num, new_hcv));
-                    }
-                },
-                (_, &HeapCellValue::Str(cell_num)) => {
-                    let new_hcv = self.follow(hcv.1);
-                    self.state_stack.push((cell_num, new_hcv));
-                }
-            }
-        }
-
-        None
-    }
-}

src/l2/iterators.rs

@@ -1,175 +0,0 @@
-use l2::ast::*;
-
-use std::cell::Cell;
-use std::collections::VecDeque;
-use std::vec::Vec;
-
-enum IteratorState<'a> {
-    Atom(Level, &'a Cell<RegType>, &'a Atom),
-    Clause(Level, usize, &'a Cell<RegType>, &'a Atom, &'a Vec<Box<Term>>),
-    IsolatedAtom(&'a Cell<RegType>, &'a Atom),
-    IsolatedVar(&'a Cell<VarReg>, &'a Var),
-    RootClause(usize, &'a Vec<Box<Term>>),
-    Var(Level, &'a Cell<VarReg>, &'a Var)
-}
-
-impl<'a> IteratorState<'a> {
-    fn to_state(lvl: Level, term: &'a Term) -> IteratorState<'a>
-    {
-        match term {
-            &Term::Atom(ref cell, ref atom) =>
-                IteratorState::Atom(lvl, cell, atom),
-            &Term::Clause(ref cell, ref atom, ref child_terms) =>
-                IteratorState::Clause(lvl, 0, cell, atom, child_terms),
-            &Term::Var(ref cell, ref var) =>
-                IteratorState::Var(lvl, cell, var)
-        }
-    }
-}
-
-pub struct QueryIterator<'a> {
-    state_stack: Vec<IteratorState<'a>>
-}
-
-impl<'a> QueryIterator<'a> {
-    fn push_clause(&mut self,
-                   lvl: Level,
-                   child_num: usize,
-                   cell: &'a Cell<RegType>,
-                   name: &'a Atom,
-                   child_terms: &'a Vec<Box<Term>>)
-    {
-        self.state_stack.push(IteratorState::Clause(lvl,
-                                                    child_num,
-                                                    cell,
-                                                    name,
-                                                    child_terms));
-    }
-
-    fn push_root_clause(&mut self,
-                        child_num: usize,
-                        child_terms: &'a Vec<Box<Term>>)
-    {
-        self.state_stack.push(IteratorState::RootClause(child_num, child_terms));
-    }
-
-    fn push_subterm(&mut self, lvl: Level, term: &'a Term) {
-        self.state_stack.push(IteratorState::to_state(lvl, term));
-    }
-
-    fn new(term: &'a Term) -> QueryIterator<'a> {
-        let state = match term {
-            &Term::Atom(ref cell, ref atom) =>
-                IteratorState::IsolatedAtom(cell, atom),
-            &Term::Clause(_, _, ref terms) =>
-                IteratorState::RootClause(0, terms),
-            &Term::Var(ref cell, ref var) =>
-                IteratorState::IsolatedVar(cell, var)
-        };
-
-        QueryIterator { state_stack: vec![state] }
-    }
-}
-
-impl<'a> Iterator for QueryIterator<'a> {
-    type Item = TermRef<'a>;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        while let Some(iter_state) = self.state_stack.pop() {
-            match iter_state {
-                IteratorState::Atom(lvl, cell, atom) =>
-                    return Some(TermRef::Atom(lvl, cell, atom)),
-                IteratorState::Clause(lvl, child_num, cell, atom, child_terms) => {
-                    if child_num == child_terms.len() {
-                        return Some(TermRef::Clause(lvl, cell, atom, child_terms));
-                    } else {
-                        self.push_clause(lvl, child_num + 1, cell, atom, child_terms);
-                        self.push_subterm(Level::Deep, child_terms[child_num].as_ref());
-                    }
-                },
-                IteratorState::IsolatedAtom(cell, atom) =>
-                    return Some(TermRef::Atom(Level::Shallow, cell, atom)),
-                IteratorState::IsolatedVar(cell, var) =>
-                    return Some(TermRef::Var(Level::Shallow, cell, var)),
-                IteratorState::RootClause(child_num, child_terms) => {
-                    if child_num == child_terms.len() {
-                        return None;
-                    } else {
-                        self.push_root_clause(child_num + 1, child_terms);
-                        self.push_subterm(Level::Shallow, child_terms[child_num].as_ref());
-                    }
-                },
-                IteratorState::Var(lvl, cell, var) =>
-                    return Some(TermRef::Var(lvl, cell, var))
-            };
-        }
-
-        None
-    }
-}
-
-pub struct FactIterator<'a> {
-    state_queue: VecDeque<IteratorState<'a>>,
-}
-
-impl<'a> FactIterator<'a> {
-    fn push_subterm(&mut self, lvl: Level, term: &'a Term) {
-        self.state_queue.push_back(IteratorState::to_state(lvl, term));
-    }
-
-    fn new(term: &'a Term) -> FactIterator<'a> {
-        let states = match term {
-            &Term::Atom(ref cell, ref atom) =>
-                vec![IteratorState::IsolatedAtom(cell, atom)],
-            &Term::Clause(_, _, ref terms) =>
-                vec![IteratorState::RootClause(0, terms)],
-            &Term::Var(ref cell, ref var) =>
-                vec![IteratorState::IsolatedVar(cell, var)]
-        };
-
-        FactIterator { state_queue:  VecDeque::from(states) }
-    }
-}
-
-impl<'a> Iterator for FactIterator<'a> {
-    type Item = TermRef<'a>;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        while let Some(state) = self.state_queue.pop_front() {
-            match state {
-                IteratorState::Atom(lvl, cell, atom) =>
-                    return Some(TermRef::Atom(lvl, cell, atom)),
-                IteratorState::Clause(lvl, _, cell, atom, child_terms) => {
-                    for child_term in child_terms {
-                        self.push_subterm(Level::Deep, child_term);
-                    }
-
-                    return Some(TermRef::Clause(lvl, cell, atom, child_terms));
-                },
-                IteratorState::IsolatedAtom(cell, atom) =>
-                    return Some(TermRef::Atom(Level::Shallow, cell, atom)),
-                IteratorState::IsolatedVar(cell, var) =>
-                    return Some(TermRef::Var(Level::Shallow, cell, var)),
-                IteratorState::RootClause(_, child_terms) => {
-                    for child_term in child_terms {
-                        self.push_subterm(Level::Shallow, child_term);
-                    }
-                },
-                IteratorState::Var(lvl, cell, var) =>
-                    return Some(TermRef::Var(lvl, cell, var))
-            }
-        }
-
-        None
-    }
-}
-
-impl Term {
-    pub fn post_order_iter(&self) -> QueryIterator {
-        QueryIterator::new(self)
-    }
-
-    pub fn breadth_first_iter(&self) -> FactIterator {
-        FactIterator::new(self)
-    }
-}

src/l2/l2_parser.lalrpop

@@ -1,45 +0,0 @@
-use l2::ast::*;
-
-use std::cell::Cell;
-
-grammar;
-
-pub TopLevel: TopLevel = {
-    "?-" <t:Term> "." => TopLevel::Query(t),
-    <r:Rule> "."      => TopLevel::Rule(r),
-    <t:Term> "."      => TopLevel::Fact(t),
-};
-
-Atom : Atom = {
-    r"[a-z][a-z0-9_]*" => <>.trim().to_string(),
-};
-
-BoxedTerm : Box<Term> = {
-    <t:Term> => Box::new(t),
-};
-
-Clause : Term = {
-    <a:Atom> "(" <ts: (<BoxedTerm> ",")*> <t:BoxedTerm> ")" => {
-     	let mut ts = ts;
-     	ts.push(t);
-	Term::Clause(Cell::new(RegType::Temp(0)), a, ts)
-    },
-};
-
-Rule : Rule = {
-    <c:Clause> ":-" <h:Term> <cs: ("," <Term>)*> =>
-         Rule { head: (c, h), clauses: cs },
-    <a:Atom> ":-" <h:Term> <cs: ("," <Term>)*> =>
-         Rule { head: (Term::Atom(Cell::new(RegType::Temp(0)), a), h),
-	        clauses: cs }
-};
-
-Term : Term = {
-    <Clause> => <>,
-    <Atom> => Term::Atom(Cell::new(RegType::Temp(0)), <>),
-    <Var>  => Term::Var(Cell::new(VarReg::Norm(RegType::Temp(0))), <>),
-};
-
-Var : Var = {
-    r"[A-Z][a-z0-9_]*" => <>.trim().to_string(),
-};

src/l2/machine.rs

@@ -1,456 +0,0 @@
-use l2::ast::*;
-use l2::codegen::*;
-use l2::heapview::*;
-use l2::stack::*;
-
-use std::collections::HashMap;
-use std::vec::Vec;
-
-#[derive(Clone, Copy)]
-enum MachineMode {
-    Read,
-    Write
-}
-
-struct MachineState {
-    h: usize,
-    s: usize,
-    p: CodePtr,
-    cp: CodePtr,
-    fail: bool,
-    heap: Heap,
-    mode: MachineMode,
-    stack: Stack,
-    registers: Registers
-}
-
-type CodeDir = HashMap<(Atom, usize), usize>;
-
-pub struct Machine {
-    ms: MachineState,
-    code: Code,
-    code_dir: CodeDir
-}
-
-impl Machine {
-    pub fn new() -> Self {
-        Machine {
-            ms: MachineState::new(),
-            code: Vec::new(),
-            code_dir: HashMap::new()
-        }
-    }
-
-    pub fn failed(&self) -> bool {
-        self.ms.fail
-    }
-
-    pub fn add_fact(&mut self, fact: &Term, mut code: Code) {
-        let p = self.code.len();
-        let name  = fact.name().clone();
-        let arity = fact.arity();
-
-        self.code.append(&mut code);
-        self.code_dir.insert((name, arity), p);
-    }
-
-    pub fn add_rule(&mut self, rule: &Rule, mut code: Code) {
-        let p = self.code.len();
-        let name  = rule.head.0.name().clone();
-        let arity = rule.head.0.arity();
-
-        self.code.append(&mut code);
-        self.code_dir.insert((name, arity), p);
-    }
-
-    fn execute_instr(&mut self, instr: &Line) -> bool {
-        let mut instr = instr;
-
-        loop {
-            match instr {
-                &Line::Fact(ref fact) => {
-                    for fact_instr in fact {
-                        self.ms.execute_fact_instr(&fact_instr);
-                    }
-                    self.ms.p += 1;
-                },
-                &Line::Query(ref query) => {
-                    for query_instr in query {
-                        self.ms.execute_query_instr(&query_instr);
-                    }
-                    self.ms.p += 1;
-                },
-                &Line::Control(ref control_instr) =>
-                    self.ms.execute_ctrl_instr(&self.code_dir, control_instr),
-            }
-
-            if self.failed() {
-                return false;
-            }
-
-            match self.ms.p {
-                CodePtr::DirEntry(p) if p < self.code.len() =>
-                    instr = &self.code[p],
-                _ => break
-            }
-        }
-
-        true
-    }
-
-    fn heap_view(&self, var_dir: HashMap<&Var, HeapCellRef>) -> String {
-        let mut result = String::new();
-
-        for (var, hcr) in var_dir {
-            let mut arities = Vec::new();
-            let viewer = HeapCellViewer::new(&self.ms.heap, hcr.heap_offset());
-
-            if result != "" {
-                result += "\n";
-            }
-
-            result += var.as_str();
-            result += " = ";
-
-            for view in viewer {
-                match arities.pop() {
-                    Some(n) => arities.push(n-1),
-                    None => {}
-                }
-
-                if !(arities.is_empty() || result.ends_with("(")) {
-                    result += ", ";
-                }
-
-                match view {
-                    HeapCellView::Str(arity, ref name) => {
-                        result += name.as_str();
-
-                        if arity > 0 {
-                            arities.push(arity);
-                            result += "(";
-                        }
-                    },
-                    HeapCellView::Var(cell_num) => {
-                        result += "_";
-                        result += cell_num.to_string().as_str();
-                    }
-                }
-
-                while let Some(&0) = arities.last() {
-                    result += ")";
-                    arities.pop();
-                }
-            }
-        }
-
-        result
-    }
-
-    pub fn run_query(&mut self, code: Code, cg: &CodeGenerator) -> Option<String>
-    {
-        let mut succeeded = true;
-
-        for instr in code.iter().take(1) {
-            succeeded = self.execute_instr(&instr);
-        }
-
-        let mut heap_locs = HashMap::new();
-
-        if succeeded {            
-            for (var, vr) in cg.vars() {
-                let hcr = self.ms.registers[vr.root_register()];
-                heap_locs.insert(*var, hcr);
-            }
-
-            for instr in code.iter().skip(1) {
-                succeeded = self.execute_instr(&instr);
-                if !succeeded {
-                    break;
-                }
-            }
-        }
-        
-        if succeeded {
-            Some(self.heap_view(heap_locs))
-        } else {
-            None
-        }   
-    }
-
-    pub fn reset(&mut self) {
-        self.ms.reset();
-    }
-}
-
-impl MachineState {
-    fn new() -> MachineState {
-        MachineState { h: 0,
-                       s: 0,
-                       p: CodePtr::TopLevel,
-                       cp: CodePtr::TopLevel,
-                       fail: false,
-                       heap: Vec::with_capacity(256),
-                       mode: MachineMode::Write,
-                       stack: Stack::new(),
-                       registers: vec![HeapCellRef::Ref(0); 32] }
-    }
-
-    fn register_mut(&mut self, r: RegType) -> &mut HeapCellRef {
-        match r {
-            RegType::Temp(r) => &mut self.registers[r],
-            RegType::Perm(r) => &mut self.stack[r]
-        }
-    }
-
-    fn lookup(&self, a: Addr) -> HeapCellRef {
-        match a {
-            Addr::HeapCell(r)  => self.heap[r].as_ref(r),
-            Addr::RegNum(r)    => self.registers[r],
-            Addr::StackCell(s) => self.stack[s]
-        }
-    }
-
-    fn deref(&self, a: Addr) -> Addr {
-        let mut a = a;
-
-        loop {
-            if let HeapCellRef::Ref(value) = self.lookup(a) {
-                if let Addr::HeapCell(av) = a {
-                    if value != av {
-                        a = Addr::HeapCell(value);
-                        continue;
-                    }
-                } else {
-                    a = Addr::HeapCell(value);
-                    continue;
-                }
-            }
-
-            return a;
-        };
-    }
-
-    fn is_unbound(hc: &HeapCellValue, index: usize) -> bool {
-        match hc {
-            &HeapCellValue::Ref(r) => r == index,
-            _ => false
-        }
-    }
-
-    fn bind(&mut self, a: Addr, val: usize) {
-        let mut a = a;
-
-        loop {
-            match a {
-                addr @ Addr::RegNum(_) | addr @ Addr::StackCell(_) => {
-                    if let HeapCellRef::Ref(hc) = self.lookup(addr) {
-                        a = Addr::HeapCell(hc);
-                    } else if Self::is_unbound(&self.heap[val], val) {
-                        self.heap[val] = HeapCellValue::from(self.lookup(addr));
-                        break;
-                    } else {
-                        self.fail = true;
-                        break;
-                    }
-                },
-                Addr::HeapCell(hc) => {
-                    if Self::is_unbound(&self.heap[hc], hc) {
-                        self.heap[hc] = HeapCellValue::Ref(val);
-                        break;
-                    } else if Self::is_unbound(&self.heap[val], val) {
-                        self.heap[val] = HeapCellValue::Ref(hc);
-                        break;
-                    } else {
-                        self.fail = true;
-                        break;
-                    }
-                }
-            };
-        }
-    }
-
-    fn unify(&mut self, a1: Addr, a2: Addr) {
-        let mut pdl = vec![a1, a2];
-
-        self.fail = false;
-
-        while !(pdl.is_empty() || self.fail) {
-            let d1 = self.deref(pdl.pop().unwrap());
-            let d2 = self.deref(pdl.pop().unwrap());
-
-            if d1 != d2 {
-                match (self.lookup(d1), self.lookup(d2)) {
-                    (HeapCellRef::Ref(hc), _) =>
-                        self.bind(d2, hc),
-                    (_, HeapCellRef::Ref(hc)) =>
-                        self.bind(d1, hc),
-                    (HeapCellRef::Str(a1), HeapCellRef::Str(a2)) => {
-                        let r1 = &self.heap[a1];
-                        let r2 = &self.heap[a2];
-
-                        if let &HeapCellValue::NamedStr(n1, ref f1) = r1 {
-                            if let &HeapCellValue::NamedStr(n2, ref f2) = r2 {
-                                if n1 == n2 && *f1 == *f2 {
-                                    for i in 1 .. n1 + 1 {
-                                        pdl.push(Addr::HeapCell(a1 + i));
-                                        pdl.push(Addr::HeapCell(a2 + i));
-                                    }
-
-                                    continue;
-                                }
-                            }
-                        }
-
-                        self.fail = true;
-                    },
-                };
-            }
-        }
-    }
-
-    fn execute_query_instr(&mut self, instr: &QueryInstruction) {
-        match instr {
-            &QueryInstruction::PutStructure(_, ref name, arity, reg) => {
-                self.heap.push(HeapCellValue::Str(self.h + 1));
-                self.heap.push(HeapCellValue::NamedStr(arity, name.clone()));
-
-                *self.register_mut(reg) = HeapCellRef::Str(self.h + 1);
-
-                self.h += 2;
-            },
-            &QueryInstruction::PutValue(norm, arg) =>
-                self.registers[arg] = match norm {
-                    RegType::Temp(reg) => self.registers[reg],
-                    RegType::Perm(reg) => self.stack[reg]
-                },
-            &QueryInstruction::PutVariable(norm, arg) => {
-                self.heap.push(HeapCellValue::Ref(self.h));
-
-                *self.register_mut(norm) = HeapCellRef::Ref(self.h);
-                self.registers[arg] = HeapCellRef::Ref(self.h);
-
-                self.h += 1;
-            },
-            &QueryInstruction::SetVariable(reg) => {
-                self.heap.push(HeapCellValue::Ref(self.h));
-                *self.register_mut(reg) = HeapCellRef::Ref(self.h);
-
-                self.h += 1;
-            },
-            &QueryInstruction::SetValue(reg) => {
-                let heap_val = self.lookup(Addr::from(reg));
-                self.heap.push(HeapCellValue::from(heap_val));
-
-                self.h += 1;
-            },
-        }
-    }
-
-    fn execute_fact_instr(&mut self, instr: &FactInstruction) {
-        match instr {
-            &FactInstruction::GetStructure(_, ref name, arity, reg) => {
-                let addr = self.deref(Addr::from(reg));
-
-                match self.lookup(addr) {
-                    HeapCellRef::Str(a) => {
-                        let result = &self.heap[a];
-
-                        if let &HeapCellValue::NamedStr(narity, ref str) = result {
-                            if narity == arity && *name == *str {
-                                self.s = a + 1;
-                                self.mode = MachineMode::Read;
-                            } else {
-                                self.fail = true;
-                            }
-                        }
-                    },
-                    HeapCellRef::Ref(_) => {
-                        self.heap.push(HeapCellValue::Str(self.h + 1));
-                        self.heap.push(HeapCellValue::NamedStr(arity, name.clone()));
-
-                        let h = self.h;
-
-                        self.bind(addr, h);
-
-                        self.h += 2;
-                        self.mode = MachineMode::Write;
-                    }
-                };
-            },
-            &FactInstruction::GetVariable(norm, arg) =>
-                *self.register_mut(norm) = self.registers[arg],
-            &FactInstruction::GetValue(norm, arg) =>
-                self.unify(Addr::from(norm), Addr::RegNum(arg)),
-            &FactInstruction::UnifyVariable(reg) => {
-                match self.mode {
-                    MachineMode::Read  =>
-                        *self.register_mut(reg) = self.heap[self.s].as_ref(self.s),
-                    MachineMode::Write => {
-                        self.heap.push(HeapCellValue::Ref(self.h));
-                        *self.register_mut(reg) = HeapCellRef::Ref(self.h);
-                        self.h += 1;
-                    }
-                };
-
-                self.s += 1;
-            },
-            &FactInstruction::UnifyValue(reg) => {
-                let s = self.s;
-
-                match self.mode {
-                    MachineMode::Read  =>
-                        self.unify(Addr::from(reg), Addr::HeapCell(s)),
-                    MachineMode::Write => {
-                        let heap_val = self.lookup(Addr::from(reg));
-                        self.heap.push(HeapCellValue::from(heap_val));
-                        self.h += 1;
-                    }
-                };
-
-                self.s += 1;
-            }
-        }
-    }
-
-    fn execute_ctrl_instr(&mut self, code_dir: &CodeDir, instr: &ControlInstruction)
-    {
-        match instr {
-            &ControlInstruction::Allocate(num_cells) => {
-                self.stack.push(self.cp, num_cells);
-                self.p += 1;
-            },
-            &ControlInstruction::Call(ref name, arity) => {
-                let compiled_tl_index = code_dir.get(&(name.clone(), arity))
-                                                .map(|index| *index);
-
-                match compiled_tl_index {
-                    Some(compiled_tl_index) => {
-                        self.cp = self.p + 1;
-                        self.p  = CodePtr::DirEntry(compiled_tl_index);
-                    },
-                    None => self.fail = true
-                };
-            },
-            &ControlInstruction::Deallocate => {
-                self.p = self.stack.get_cp();
-                self.stack.pop();
-            },
-            &ControlInstruction::Proceed =>
-                self.p = self.cp,
-        };
-    }
-
-    fn reset(&mut self) {
-        self.h = 0;
-        self.s = 0;
-        self.p = CodePtr::TopLevel;
-        self.cp = CodePtr::TopLevel;
-
-        self.fail = false;
-        self.heap.clear();
-        self.mode = MachineMode::Write;
-        self.stack = Stack::new();
-        self.registers = vec![HeapCellRef::Ref(0); 32];
-    }
-}

src/l2/mod.rs

@@ -1,7 +0,0 @@
-pub mod ast;
-pub mod heapview;
-pub mod iterators;
-pub mod l2_parser;
-pub mod codegen;
-pub mod machine;
-pub mod stack;

src/l2/stack.rs

@@ -1,60 +0,0 @@
-use l2::ast::*;
-
-use std::ops::{Index, IndexMut};
-use std::vec::Vec;
-
-struct Frame {
-    cp: CodePtr,
-    perms: Vec<HeapCellRef>
-}
-
-impl Frame {
-    fn new(cp: CodePtr, n: usize) -> Self {
-        Frame {
-            cp: cp,
-            perms: vec![HeapCellRef::Ref(0); n]
-        }
-    }
-
-    fn read_pv(&self, i: usize) -> &HeapCellRef {
-        self.perms.index(i)
-    }
-
-    fn read_pv_mut(&mut self, i: usize) -> &mut HeapCellRef {
-        self.perms.index_mut(i)
-    }
-}
-
-pub struct Stack(Vec<Frame>);
-
-impl Stack {
-    pub fn new() -> Self {
-        Stack(Vec::new())
-    }
-    
-    pub fn push(&mut self, cp: CodePtr, n: usize) {
-        self.0.push(Frame::new(cp, n));
-    }
-
-    pub fn get_cp(&self) -> CodePtr {
-        self.0.last().unwrap().cp
-    }
-    
-    pub fn pop(&mut self) {
-        self.0.pop();
-    }
-}
-
-impl Index<usize> for Stack {
-    type Output = HeapCellRef;
-
-    fn index(&self, index: usize) -> &Self::Output {
-        self.0.last().unwrap().read_pv(index - 1)
-    }
-}
-
-impl IndexMut<usize> for Stack {
-    fn index_mut(&mut self, index: usize) -> &mut Self::Output {
-        self.0.last_mut().unwrap().read_pv_mut(index - 1)
-    }
-}

src/l3/and_stack.rs

@@ -1,80 +0,0 @@
-use l3::ast::*;
-
-use std::ops::{Index, IndexMut};
-use std::vec::Vec;
-
-pub struct Frame {
-    pub global_index: usize,
-    pub e: usize,
-    pub cp: CodePtr,
-    perms: Vec<Addr>
-}
-
-impl Frame {
-    fn new(global_index: usize, e: usize, cp: CodePtr, n: usize) -> Self {
-        Frame {
-            global_index: global_index,
-            e: e,
-            cp: cp,
-            perms: vec![Addr::HeapCell(0); n]
-        }
-    }
-}
-
-pub struct AndStack(Vec<Frame>);
-
-impl AndStack {
-    pub fn new() -> Self {
-        AndStack(Vec::new())
-    }
-
-    pub fn push(&mut self, global_index: usize, e: usize, cp: CodePtr, n: usize) {
-        self.0.push(Frame::new(global_index, e, cp, n));
-    }
-
-    pub fn top(&self) -> Option<&Frame> {
-        self.0.last()
-    }
-
-    pub fn len(&self) -> usize {
-        self.0.len()
-    }
-
-    pub fn clear(&mut self) {
-        self.0.clear()
-    }
-
-    // drop the last n frames.
-    pub fn drop_frames(&mut self, n: usize) {
-        let len = self.0.len();
-        self.0.truncate(len - n);
-    }
-}
-
-impl Index<usize> for AndStack {
-    type Output = Frame;
-
-    fn index(&self, index: usize) -> &Self::Output {
-        self.0.index(index)
-    }
-}
-
-impl IndexMut<usize> for AndStack {
-    fn index_mut(&mut self, index: usize) -> &mut Self::Output {
-        self.0.index_mut(index)
-    }
-}
-
-impl Index<usize> for Frame {
-    type Output = Addr;
-
-    fn index(&self, index: usize) -> &Self::Output {
-        self.perms.index(index - 1)
-    }
-}
-
-impl IndexMut<usize> for Frame {
-    fn index_mut(&mut self, index: usize) -> &mut Self::Output {
-        self.perms.index_mut(index - 1)
-    }
-}

src/l3/ast.rs

@@ -1,303 +0,0 @@
-use std::cell::Cell;
-use std::collections::HashMap;
-use std::ops::{Add, AddAssign};
-use std::vec::Vec;
-
-pub type Var = String;
-
-pub type Atom = String;
-
-pub enum PredicateClause {
-    Fact(Term),
-    Rule(Rule)
-}
-
-impl PredicateClause {
-    pub fn name(&self) -> &Atom {
-        match self {
-            &PredicateClause::Fact(ref t) => t.name(),
-            &PredicateClause::Rule(ref rule) => rule.head.0.name()
-        }
-    }
-
-    pub fn arity(&self) -> usize {
-        match self {
-            &PredicateClause::Fact(ref t) => t.arity(),
-            &PredicateClause::Rule(ref rule) => rule.head.0.arity()
-        }
-    }
-}
-
-pub enum TopLevel {
-    Fact(Term),
-    Predicate(Vec<PredicateClause>),
-    Query(Term),
-    Rule(Rule)
-}
-
-#[derive(Clone, Copy)]
-pub enum Level {
-    Deep, Shallow
-}
-
-#[derive(Clone, Copy)]
-pub enum RegType {
-    Perm(usize),
-    Temp(usize)
-}
-
-impl RegType {
-    pub fn reg_num(self) -> usize {
-        match self {
-            RegType::Perm(reg_num) | RegType::Temp(reg_num) => reg_num
-        }
-    }
-
-    pub fn is_perm(self) -> bool {
-        match self {
-            RegType::Perm(_) => true,
-            _ => false
-        }
-    }
-}
-
-#[derive(Clone, Copy)]
-pub enum VarReg {
-    ArgAndNorm(RegType, usize),
-    Norm(RegType)
-}
-
-impl VarReg {
-    pub fn norm(self) -> RegType {
-        match self {
-            VarReg::ArgAndNorm(reg, _) | VarReg::Norm(reg) => reg
-        }
-    }
-
-    pub fn root_register(self) -> usize {
-        match self {
-            VarReg::ArgAndNorm(_, root) => root,
-            VarReg::Norm(root) => root.reg_num()
-        }
-    }
-}
-
-pub enum Term {
-    Atom(Cell<RegType>, Atom),
-    Clause(Cell<RegType>, Atom, Vec<Box<Term>>),
-    Var(Cell<VarReg>, Var)
-}
-
-pub struct Rule {
-    pub head: (Term, Term),
-    pub clauses: Vec<Term>
-}
-
-pub enum TermRef<'a> {
-    Atom(Level, &'a Cell<RegType>, &'a Atom),
-    Clause(Level, &'a Cell<RegType>, &'a Atom, &'a Vec<Box<Term>>),
-    Var(Level, &'a Cell<VarReg>, &'a Var)
-}
-
-pub enum FactInstruction {
-    GetStructure(Level, Atom, usize, RegType),
-    GetValue(RegType, usize),
-    GetVariable(RegType, usize),
-    UnifyVariable(RegType),
-    UnifyValue(RegType)
-}
-
-pub enum QueryInstruction {
-    PutStructure(Level, Atom, usize, RegType),
-    PutValue(RegType, usize),
-    PutVariable(RegType, usize),
-    SetVariable(RegType),
-    SetValue(RegType)
-}
-
-pub enum ChoiceInstruction {
-    RetryMeElse(usize),
-    TrustMe,
-    TryMeElse(usize)
-}
-
-pub enum ControlInstruction {
-    Allocate(usize),
-    Call(Atom, usize),
-    Deallocate,
-    Proceed
-}
-
-pub type CompiledFact = Vec<FactInstruction>;
-
-pub type CompiledQuery = Vec<QueryInstruction>;
-
-pub enum Line {
-    Choice(ChoiceInstruction),
-    Control(ControlInstruction),
-    Fact(CompiledFact),
-    Query(CompiledQuery)
-}
-
-pub enum LineOrCodeOffset<'a> {
-    Instruction(&'a Line),
-    Offset(usize)
-}
-
-impl<'a> From<&'a Line> for LineOrCodeOffset<'a> {
-    fn from(line: &'a Line) -> Self {
-        LineOrCodeOffset::Instruction(line)
-    }
-}
-
-pub type Code = Vec<Line>;
-
-#[derive(Clone, Copy, PartialEq)]
-pub enum Addr {
-    HeapCell(usize),
-    StackCell(usize, usize),
-    Str(usize)
-}
-
-impl Addr {
-    pub fn is_ref(self) -> bool {
-        match self {
-            Addr::HeapCell(_) | Addr::StackCell(_, _) => true,
-            _ => false
-        }
-    }
-
-    pub fn as_ref(self) -> Option<Ref> {
-        match self {
-            Addr::HeapCell(hc) => Some(Ref::HeapCell(hc)),
-            Addr::StackCell(fr, sc) => Some(Ref::StackCell(fr, sc)),
-            _ => None
-        }
-    }
-}
-
-impl From<Ref> for Addr {
-    fn from(r: Ref) -> Self {
-        match r {
-            Ref::HeapCell(hc) => Addr::HeapCell(hc),
-            Ref::StackCell(fr, sc) => Addr::StackCell(fr, sc)
-        }
-    }
-}
-
-#[derive(Clone, Copy, PartialEq)]
-pub enum Ref {
-    HeapCell(usize),
-    StackCell(usize, usize)
-}
-
-#[derive(Clone, PartialEq)]
-pub enum HeapCellValue {
-    NamedStr(usize, Atom),
-    Ref(Ref),
-    Str(usize)
-}
-
-impl From<Addr> for HeapCellValue {
-    fn from(addr: Addr) -> HeapCellValue {
-        match addr {
-            Addr::HeapCell(hc) =>
-                HeapCellValue::Ref(Ref::HeapCell(hc)),
-            Addr::StackCell(fr, sc) =>
-                HeapCellValue::Ref(Ref::StackCell(fr, sc)),
-            Addr::Str(hc) =>
-                HeapCellValue::Str(hc)
-        }
-    }
-}
-
-impl HeapCellValue {
-    pub fn as_addr(&self, focus: usize) -> Addr {
-        match self {           
-            &HeapCellValue::Ref(r) => Addr::from(r),
-            &HeapCellValue::Str(s) => Addr::Str(s),
-            &HeapCellValue::NamedStr(_, _) => Addr::Str(focus)
-        }
-    }
-}
-
-#[derive(Clone, Copy)]
-pub enum CodePtr {
-    DirEntry(usize),
-    TopLevel
-}
-
-impl Default for CodePtr {
-    fn default() -> Self {
-        CodePtr::TopLevel
-    }
-}
-
-impl Add<usize> for CodePtr {
-    type Output = CodePtr;
-
-    fn add(self, rhs: usize) -> Self::Output {
-        match self {
-            CodePtr::DirEntry(p) => CodePtr::DirEntry(p + rhs),
-            CodePtr::TopLevel => CodePtr::TopLevel
-        }
-    }
-}
-
-impl AddAssign<usize> for CodePtr {
-    fn add_assign(&mut self, rhs: usize) {
-        match self {
-            &mut CodePtr::DirEntry(ref mut p) => *p += rhs,
-            _ => {}
-        }
-    }
-}
-
-pub type Heap = Vec<HeapCellValue>;
-
-pub type Registers = Vec<Addr>;
-
-impl Term {
-    pub fn subterms(&self) -> usize {
-        match self {
-            &Term::Clause(_, _, ref terms) => terms.len(),
-            _ => 1
-        }
-    }
-
-    pub fn name(&self) -> &Atom {
-        match self {
-            &Term::Atom(_, ref atom)
-            | &Term::Var(_, ref atom)
-            | &Term::Clause(_, ref atom, _) => atom
-        }
-    }
-
-    pub fn arity(&self) -> usize {
-        match self {
-            &Term::Atom(_, _) | &Term::Var(_, _) => 0,
-            &Term::Clause(_, _, ref child_terms) => child_terms.len()
-        }
-    }
-}
-
-pub type HeapVarDict = HashMap<Var, Addr>;
-
-pub enum EvalResult {
-    EntryFailure,
-    EntrySuccess,
-    InitialQuerySuccess(HeapVarDict),
-    QueryFailure,
-    SubsequentQuerySuccess,
-}
-
-impl EvalResult {
-    #[allow(dead_code)]
-    pub fn failed_query(&self) -> bool {
-        if let &EvalResult::QueryFailure = self {
-            true
-        } else {
-            false
-        }
-    }
-}

src/l3/codegen.rs

@@ -1,447 +0,0 @@
-use l3::ast::*;
-use l3::iterators::{FactIterator, QueryIterator};
-
-use std::cell::Cell;
-use std::cmp::max;
-use std::collections::HashMap;
-use std::vec::Vec;
-
-trait CompilationTarget<'a> {
-    type Iterator : Iterator<Item=TermRef<'a>>;
-
-    fn iter(&'a Term) -> Self::Iterator;
-
-    fn to_structure(Level, Atom, usize, RegType) -> Self;
-
-    fn argument_to_variable(RegType, usize) -> Self;
-    fn argument_to_value(RegType, usize) -> Self;
-    fn subterm_to_variable(RegType) -> Self;
-    fn subterm_to_value(RegType) -> Self;
-
-    fn clause_arg_to_instr(RegType) -> Self;
-}
-
-impl<'a> CompilationTarget<'a> for FactInstruction {
-    type Iterator = FactIterator<'a>;
-
-    fn iter(term: &'a Term) -> Self::Iterator {
-        term.breadth_first_iter()
-    }
-
-    fn to_structure(lvl: Level, atom: Atom, arity: usize, reg: RegType) -> Self {
-        FactInstruction::GetStructure(lvl, atom, arity, reg)
-    }
-
-    fn argument_to_variable(arg: RegType, val: usize) -> Self {
-        FactInstruction::GetVariable(arg, val)
-    }
-
-    fn argument_to_value(arg: RegType, val: usize) -> Self {
-        FactInstruction::GetValue(arg, val)
-    }
-
-    fn subterm_to_variable(val: RegType) -> Self {
-        FactInstruction::UnifyVariable(val)
-    }
-
-    fn subterm_to_value(val: RegType) -> Self {
-        FactInstruction::UnifyValue(val)
-    }
-
-    fn clause_arg_to_instr(val: RegType) -> Self {
-        FactInstruction::UnifyVariable(val)
-    }
-}
-
-impl<'a> CompilationTarget<'a> for QueryInstruction {
-    type Iterator = QueryIterator<'a>;
-
-    fn iter(term: &'a Term) -> Self::Iterator {
-        term.post_order_iter()
-    }
-
-    fn to_structure(lvl: Level, atom: Atom, arity: usize, reg: RegType) -> Self {
-        QueryInstruction::PutStructure(lvl, atom, arity, reg)
-    }
-
-    fn argument_to_variable(arg: RegType, val: usize) -> Self {
-        QueryInstruction::PutVariable(arg, val)
-    }
-
-    fn argument_to_value(arg: RegType, val: usize) -> Self {
-        QueryInstruction::PutValue(arg, val)
-    }
-
-    fn subterm_to_variable(val: RegType) -> Self {
-        QueryInstruction::SetVariable(val)
-    }
-
-    fn subterm_to_value(val: RegType) -> Self {
-        QueryInstruction::SetValue(val)
-    }
-
-    fn clause_arg_to_instr(val: RegType) -> Self {
-        QueryInstruction::SetValue(val)
-    }
-}
-
-struct TermMarker<'a> {
-    bindings: HashMap<&'a Var, VarReg>,
-    arg_c:    usize,
-    perm_c:   usize,
-    temp_c:   usize
-}
-
-impl<'a> TermMarker<'a> {
-    fn new() -> TermMarker<'a> {
-        TermMarker { bindings: HashMap::new(),
-                     arg_c:    1,
-                     perm_c:   1,
-                     temp_c:   1 }
-    }
-
-    fn reset(&mut self) {
-        self.bindings.clear();
-        self.perm_c = 1;
-    }
-    
-    fn contains_var(&self, var: &'a Var) -> bool {
-        self.bindings.contains_key(var)
-    }
-
-    fn get(&self, var: &'a Var) -> VarReg {
-        *self.bindings.get(var).unwrap()
-    }
-
-    fn insert(&mut self, var: &'a Var, r: VarReg) {
-        self.bindings.insert(var, r);
-    }
-
-    fn mark_non_var(&mut self, lvl: Level, cell: &Cell<RegType>) {
-        let reg_type = cell.get();
-
-        if reg_type.reg_num() == 0 {
-            match lvl {
-                Level::Deep if reg_type.is_perm() => {
-                    let perm = self.perm_c;
-                    self.perm_c += 1;
-                    cell.set(RegType::Perm(perm));
-                },
-                Level::Deep => {
-                    let temp = self.temp_c;
-                    self.temp_c += 1;
-                    cell.set(RegType::Temp(temp));
-                },
-                Level::Shallow if reg_type.is_perm() => {
-                    let arg = self.arg_c;
-                    self.arg_c += 1;
-                    cell.set(RegType::Perm(arg));
-                },
-                Level::Shallow => {
-                    let arg = self.arg_c;
-                    self.arg_c += 1;
-                    cell.set(RegType::Temp(arg));
-                }
-            };
-        }
-    }
-
-    fn mark_old_var(&mut self, lvl: Level, var: &'a Var) -> VarReg
-    {
-        let reg = self.get(var);
-
-        match lvl {
-            Level::Deep => VarReg::Norm(reg.norm()),
-            Level::Shallow => {
-                let reg = VarReg::ArgAndNorm(reg.norm(), self.arg_c);
-
-                self.arg_c += 1;
-                self.insert(var, reg);
-
-                reg
-            }
-        }
-    }
-
-    fn mark_new_var(&mut self, lvl: Level, var: &'a Var, reg: RegType) -> VarReg
-    {
-        let inner_reg = if reg.is_perm() {
-            let perm = self.perm_c;
-            self.perm_c += 1;
-            RegType::Perm(perm)
-        } else {
-            let temp = self.temp_c;
-            self.temp_c += 1;
-            RegType::Temp(temp)
-        };
-
-        let reg = match lvl {
-            Level::Deep => VarReg::Norm(inner_reg),
-            Level::Shallow => {
-                let reg = VarReg::ArgAndNorm(inner_reg, self.arg_c);
-                self.arg_c += 1;
-                reg
-            }
-        };
-
-        self.insert(var, reg);
-        reg
-    }
-
-    fn advance_at_head(&mut self, term: &'a Term) {
-        self.arg_c = 1;
-        self.temp_c = max(term.subterms(), self.temp_c) + 1;
-    }
-
-    fn advance(&mut self, term: &'a Term) {
-        self.arg_c = 1;
-        self.temp_c = term.subterms() + 1;
-    }
-}
-
-#[derive(Copy, Clone)]
-enum TermStatus {
-    New, Old, Recurrent
-}
-
-pub struct CodeGenerator<'a> {
-    marker: TermMarker<'a>
-}
-
-type VariableFixture<'a>  = (TermStatus, Vec<&'a Cell<VarReg>>);
-type VariableFixtures<'a> = HashMap<&'a Var, VariableFixture<'a>>;
-
-impl<'a> CodeGenerator<'a> {
-    pub fn new() -> Self {
-        CodeGenerator { marker: TermMarker::new() }
-    }
-
-    pub fn vars(&self) -> &HashMap<&Var, VarReg> {
-        &self.marker.bindings
-    }
-
-    fn to_structure<Target>(&mut self,
-                            lvl: Level,
-                            name: &'a Atom,
-                            cell: &'a Cell<RegType>,
-                            arity: usize)
-                            -> Target
-        where Target: CompilationTarget<'a>
-    {
-        self.marker.mark_non_var(lvl, cell);
-        Target::to_structure(lvl, name.clone(), arity, cell.get())
-    }
-
-    fn var_term<Target>(&mut self,
-                        lvl: Level,
-                        cell: &'a Cell<VarReg>,
-                        var: &'a Var)
-                        -> Target
-        where Target: CompilationTarget<'a>
-    {
-        if !self.marker.contains_var(var) {
-            let reg = self.marker.mark_new_var(lvl, var, cell.get().norm());
-            cell.set(reg);
-
-            match reg {
-                VarReg::ArgAndNorm(arg, norm) =>
-                    Target::argument_to_variable(arg, norm),
-                VarReg::Norm(norm) =>
-                    Target::subterm_to_variable(norm)
-            }
-        } else {
-            let reg = self.marker.mark_old_var(lvl, var);
-            cell.set(reg);
-
-            match reg {
-                VarReg::ArgAndNorm(arg, norm) =>
-                    Target::argument_to_value(arg, norm),
-                VarReg::Norm(norm) =>
-                    Target::subterm_to_value(norm)
-            }
-        }
-    }
-
-    fn non_var_subterm<Target>(&mut self, cell: &'a Cell<RegType>) -> Target
-        where Target: CompilationTarget<'a>
-    {
-        self.marker.mark_non_var(Level::Deep, cell);
-        Target::clause_arg_to_instr(cell.get())
-    }
-
-    fn subterm_to_instr<Target>(&mut self, subterm: &'a Term) -> Target
-        where Target: CompilationTarget<'a>
-    {
-        match subterm {
-            &Term::Atom(ref cell, _) | &Term::Clause(ref cell, _, _) =>
-                self.non_var_subterm(cell),
-            &Term::Var(ref cell, ref var) =>
-                self.var_term(Level::Deep, cell, var)
-        }
-    }
-
-    fn compile_target<Target>(&mut self, term: &'a Term) -> Vec<Target>
-        where Target: CompilationTarget<'a>
-    {
-        let iter       = Target::iter(term);
-        let mut target = Vec::new();
-
-        for term in iter {
-            match term {
-                TermRef::Atom(lvl, term, atom) =>
-                    target.push(self.to_structure(lvl, atom, term, 0)),
-                TermRef::Clause(lvl, term, atom, terms) => {
-                    target.push(self.to_structure(lvl, atom, term, terms.len()));
-
-                    for subterm in terms {
-                        target.push(self.subterm_to_instr(subterm.as_ref()));
-                    }
-                },
-                TermRef::Var(lvl @ Level::Shallow, ref cell, ref var) =>
-                    target.push(self.var_term(lvl, cell, var)),
-                _ => {}
-            };
-        }
-
-        target
-    }
-
-    fn mark_vars_in_term<Iter>(iter: Iter, vs: &mut VariableFixtures<'a>)
-        where Iter : Iterator<Item=TermRef<'a>>
-    {
-        for term in iter {
-            if let TermRef::Var(_, reg_cell, var) = term {
-                let mut status = vs.entry(var)
-                                   .or_insert((TermStatus::New, Vec::new()));
-
-                status.1.push(reg_cell);
-
-                match status.0 {
-                    TermStatus::Old => status.0 = TermStatus::Recurrent,
-                    _ => {}
-                };
-            }
-        }
-
-        for &mut (ref mut term_status, ref mut cb) in vs.values_mut() {
-            match *term_status {
-                TermStatus::New => *term_status = TermStatus::Old,
-                TermStatus::Recurrent => {
-                    for cell_reg in cb.drain(0..) {
-                        cell_reg.set(VarReg::Norm(RegType::Perm(0)));
-                    }
-                },
-                _ => {}
-            }
-        }
-    }
-
-    fn mark_perm_vars(rule: &'a Rule) -> VariableFixtures {
-        let &Rule { head: (ref p0, ref p1), ref clauses } = rule;
-        let mut vfs = HashMap::new();
-
-        let iter = p0.breadth_first_iter().chain(p1.breadth_first_iter());
-
-        Self::mark_vars_in_term(iter, &mut vfs);
-
-        for term in clauses {
-            Self::mark_vars_in_term(term.breadth_first_iter(), &mut vfs);
-        }
-
-        vfs
-    }
-
-    fn add_conditional_call(compiled_query: &mut Code, term: &Term) {
-        match term {
-            &Term::Atom(_, ref atom) => {
-                let call = ControlInstruction::Call(atom.clone(), 0);
-                compiled_query.push(Line::Control(call));
-            },
-            &Term::Clause(_, ref atom, ref terms) => {
-                let call = ControlInstruction::Call(atom.clone(), terms.len());
-                compiled_query.push(Line::Control(call));
-            },
-            _ => {}
-        }
-    }
-
-    pub fn compile_rule(&mut self, rule: &'a Rule) -> Code {
-        let vfs = Self::mark_perm_vars(&rule);
-        let &Rule { head: (ref p0, ref p1), ref clauses } = rule;
-        let mut perm_vars = 0;
-
-        for &(term_status, _) in vfs.values() {
-            if let TermStatus::Recurrent = term_status {
-                perm_vars += 1;
-            }
-        }
-
-        let mut body = Vec::new();
-
-        body.push(Line::Control(ControlInstruction::Allocate(perm_vars)));
-
-        self.marker.advance(p0);
-        body.push(Line::Fact(self.compile_target(p0)));
-
-        self.marker.advance_at_head(p1);
-        body.push(Line::Query(self.compile_target(p1)));
-        
-        Self::add_conditional_call(&mut body, p1);
-
-        body = clauses.iter()
-            .map(|ref term| self.compile_query(term))
-            .fold(body, |mut body, ref mut cqs| {
-                body.append(cqs);
-                body
-            });
-
-        body.push(Line::Control(ControlInstruction::Deallocate));
-        body
-    }
-
-    pub fn compile_fact(&mut self, term: &'a Term) -> Code {
-        self.marker.advance(term);
-
-        let mut compiled_fact = vec![Line::Fact(self.compile_target(term))];
-        let proceed = Line::Control(ControlInstruction::Proceed);
-
-        compiled_fact.push(proceed);
-        compiled_fact
-    }
-
-    pub fn compile_query(&mut self, term: &'a Term) -> Code {
-        self.marker.advance(term);
-
-        let mut compiled_query = vec![Line::Query(self.compile_target(term))];
-        Self::add_conditional_call(&mut compiled_query, term);
-
-        compiled_query
-    }
-
-    pub fn compile_predicate(&mut self, clauses: &'a Vec<PredicateClause>) -> Code
-    {
-        let mut code = Vec::new();
-        
-        for (i, clause) in clauses.iter().enumerate() {
-            self.marker.reset();
-            
-            let mut clause_code = match clause {
-                &PredicateClause::Fact(ref fact) =>
-                    self.compile_fact(fact),
-                &PredicateClause::Rule(ref rule) =>
-                    self.compile_rule(rule)
-            };
-
-            let choice = match i {
-                0 => ChoiceInstruction::TryMeElse(clause_code.len() + 1),
-                _ if i == clauses.len() - 1 => ChoiceInstruction::TrustMe,
-                _ => ChoiceInstruction::RetryMeElse(clause_code.len() + 1)
-            };
-
-            code.push(Line::Choice(choice));
-            code.append(&mut clause_code);
-        }
-
-        code
-    }
-}

src/l3/heapview.rs

@@ -1,86 +0,0 @@
-use l3::and_stack::*;
-use l3::ast::*;
-
-use std::vec::Vec;
-
-#[derive(Clone, Copy)]
-pub enum HeapCellView<'a> {
-    Str(usize, &'a Atom),
-    HeapVar(usize),
-    StackVar(usize, usize)
-}
-
-pub struct HeapCellViewer<'a> {
-    heap: &'a Heap,
-    and_stack: &'a AndStack,
-    state_stack: Vec<Addr>
-}
-
-impl<'a> HeapCellViewer<'a> {
-    pub fn new(heap: &'a Heap, and_stack: &'a AndStack, focus: Addr) -> Self {
-        HeapCellViewer {
-            heap: heap,
-            and_stack: and_stack,
-            state_stack: vec![focus]
-        }
-    }
-
-    fn follow_stack_ref(&mut self, mut fr: usize, mut sc: usize) -> HeapCellView<'a>
-    {
-        loop {
-            match self.and_stack[fr][sc] {
-                Addr::HeapCell(hc) | Addr::Str(hc) =>
-                    return self.follow_heap_ref(hc),
-                Addr::StackCell(fr1, sc1) => {
-                    if fr1 == fr && sc1 == sc {
-                        return HeapCellView::StackVar(fr, sc);
-                    }
-
-                    fr = fr1; sc = sc1;
-                }
-            }
-        }
-    }
-
-    fn follow_heap_ref(&mut self, mut focus: usize) -> HeapCellView<'a> {
-        loop {
-            match &self.heap[focus] {
-                &HeapCellValue::NamedStr(arity, ref name) => {
-                    for i in (1 .. arity + 1).rev() {
-                        self.state_stack.push(Addr::HeapCell(focus + i));
-                    }
-
-                    return HeapCellView::Str(arity, name);
-                },
-                &HeapCellValue::Ref(Ref::HeapCell(hc)) => {
-                    if focus == hc {
-                        return HeapCellView::HeapVar(hc);
-                    } else {
-                        focus = hc;
-                    }
-                },
-                &HeapCellValue::Ref(Ref::StackCell(fr, sc)) =>
-                    return self.follow_stack_ref(fr, sc),
-                &HeapCellValue::Str(cell_num) =>
-                    focus = cell_num,
-            }
-        }
-    }
-}
-
-impl<'a> Iterator for HeapCellViewer<'a> {
-    type Item = HeapCellView<'a>;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        if let Some(addr) = self.state_stack.pop() {
-            match addr {
-                Addr::HeapCell(hc) | Addr::Str(hc) =>
-                    return Some(self.follow_heap_ref(hc)),
-                Addr::StackCell(fr, sc) =>
-                    return Some(self.follow_stack_ref(fr, sc))
-            }
-        }
-
-        None
-    }
-}

src/l3/io.rs

@@ -1,255 +0,0 @@
-use l3::ast::*;
-use l3::codegen::*;
-use l3::l3_parser::*;
-use l3::machine::*;
-
-use termion::raw::IntoRawMode;
-use termion::input::TermRead;
-use termion::event::Key;
-
-use std::io::{Write, stdin, stdout};
-use std::fmt;
-
-impl fmt::Display for FactInstruction {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self {
-            &FactInstruction::GetStructure(Level::Deep, ref name, ref arity, ref r) =>
-                write!(f, "get_structure {}/{}, {}", name, arity, r),
-            &FactInstruction::GetStructure(Level::Shallow, ref name, ref arity, ref r) =>
-                write!(f, "get_structure {}/{}, A{}", name, arity, r.reg_num()),
-            &FactInstruction::GetValue(ref x, ref a) =>
-                write!(f, "get_value {}, A{}", x, a),
-            &FactInstruction::GetVariable(ref x, ref a) =>
-                write!(f, "get_variable {}, A{}", x, a),
-            &FactInstruction::UnifyVariable(ref r) =>
-                write!(f, "unify_variable {}", r),
-            &FactInstruction::UnifyValue(ref r) =>
-                write!(f, "unify_value {}", r)
-        }
-    }
-}
-
-impl fmt::Display for QueryInstruction {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self {
-            &QueryInstruction::PutStructure(Level::Deep, ref name, ref arity, ref r) =>
-                write!(f, "put_structure {}/{}, {}", name, arity, r.reg_num()),
-            &QueryInstruction::PutStructure(Level::Shallow, ref name, ref arity, ref r) =>
-                write!(f, "put_structure {}/{}, A{}", name, arity, r.reg_num()),
-            &QueryInstruction::PutValue(ref x, ref a) =>
-                write!(f, "put_value {}, A{}", x, a),
-            &QueryInstruction::PutVariable(ref x, ref a) =>
-                write!(f, "put_variable {}, A{}", x, a),
-            &QueryInstruction::SetVariable(ref r) =>
-                write!(f, "set_variable {}", r),
-            &QueryInstruction::SetValue(ref r) =>
-                write!(f, "set_value {}", r),
-        }
-    }
-}
-
-impl fmt::Display for ControlInstruction {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self {
-            &ControlInstruction::Allocate(num_cells) =>
-                write!(f, "allocate {}", num_cells),
-            &ControlInstruction::Call(ref name, ref arity) =>
-                write!(f, "call {}/{}", name, arity),
-            &ControlInstruction::Deallocate =>
-                write!(f, "deallocate"),
-            &ControlInstruction::Proceed =>
-                write!(f, "proceed")
-        }
-    }
-}
-
-impl fmt::Display for ChoiceInstruction {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self {
-            &ChoiceInstruction::TryMeElse(offset) =>
-                write!(f, "try_me_else {}", offset),
-            &ChoiceInstruction::RetryMeElse(offset) =>
-                write!(f, "retry_me_else {}", offset),
-            &ChoiceInstruction::TrustMe =>
-                write!(f, "trust_me")
-        }
-    }
-}
-
-impl fmt::Display for Level {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self {
-            &Level::Shallow => write!(f, "A"),
-            &Level::Deep => write!(f, "X")
-        }
-    }
-}
-
-impl fmt::Display for VarReg {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self {
-            &VarReg::Norm(RegType::Perm(reg)) => write!(f, "Y{}", reg),
-            &VarReg::Norm(RegType::Temp(reg)) => write!(f, "X{}", reg),
-            &VarReg::ArgAndNorm(RegType::Perm(reg), arg) =>
-                write!(f, "Y{} A{}", reg, arg),
-            &VarReg::ArgAndNorm(RegType::Temp(reg), arg) =>
-                write!(f, "X{} A{}", reg, arg)
-        }
-    }
-}
-
-impl fmt::Display for RegType {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self {
-            &RegType::Perm(val) => write!(f, "Y{}", val),
-            &RegType::Temp(val) => write!(f, "X{}", val)
-        }
-    }
-}
-
-
-fn is_consistent(predicate: &Vec<PredicateClause>) -> bool {
-    let name  = predicate.first().unwrap().name();
-    let arity = predicate.first().unwrap().arity();
-
-    for clause in predicate.iter().skip(1) {
-        if !(name == clause.name() && arity == clause.arity()) {
-            return false;
-        }
-    }
-
-    true
-}
-
-#[allow(dead_code)]
-pub fn print_code(code: &Code) {
-    for clause in code {
-        match clause {
-            &Line::Fact(ref fact) =>
-                for fact_instr in fact {
-                    println!("{}", fact_instr);
-                },
-            &Line::Choice(ref choice) =>
-                println!("{}", choice),
-            &Line::Control(ref control) =>
-                println!("{}", control),
-            &Line::Query(ref query) =>
-                for query_instr in query {
-                    println!("{}", query_instr);
-                }
-        }
-    }
-}
-
-pub fn read() -> String {
-    let _ = stdout().flush();
-
-    let mut buffer = String::new();
-    let mut result = String::new();
-
-    let stdin = stdin();
-    stdin.read_line(&mut buffer).unwrap();
-
-    if &*buffer.trim() == ":{" {
-        buffer.clear();
-
-        stdin.read_line(&mut buffer).unwrap();
-
-        while &*buffer.trim() != "}:" {
-            result += buffer.as_str();
-            buffer.clear();
-            stdin.read_line(&mut buffer).unwrap();
-        }
-    } else {
-        result = buffer;
-    }
-
-    result
-}
-
-pub fn eval(wam: &mut Machine, buffer: &str) -> EvalResult
-{
-    let result = parse_TopLevel(buffer);
-    let mut cg = CodeGenerator::new();
-
-    match &result {
-        &Ok(TopLevel::Predicate(ref clauses)) => {
-            if is_consistent(clauses) {
-                let compiled_pred = cg.compile_predicate(clauses);
-                wam.add_predicate(clauses, compiled_pred);
-
-                EvalResult::EntrySuccess
-            } else {
-                let msg = r"Error: predicate is inconsistent.
-Each predicate must have the same name and arity.";
-
-                println!("{}", msg);
-                EvalResult::EntryFailure
-            }
-        },
-        &Ok(TopLevel::Fact(ref fact)) => {
-            let compiled_fact = cg.compile_fact(&fact);
-            wam.add_fact(fact, compiled_fact);
-            EvalResult::EntrySuccess
-        },
-        &Ok(TopLevel::Rule(ref rule)) => {
-            let compiled_rule = cg.compile_rule(&rule);
-            wam.add_rule(rule, compiled_rule);
-            EvalResult::EntrySuccess
-        },
-        &Ok(TopLevel::Query(ref query)) => {
-            let compiled_query = cg.compile_query(&query);
-            wam.run_query(compiled_query, &cg)
-        },
-        &Err(_) => {
-            println!("Grammatical error of some kind!");
-            EvalResult::EntryFailure
-        }
-    }
-}
-
-pub fn print(wam: &mut Machine, result: EvalResult) {
-    match result {
-        EvalResult::InitialQuerySuccess(heap_locs) => {
-            println!("yes");
-
-            'outer: loop {
-                let mut result = EvalResult::QueryFailure;
-                let bindings = wam.heap_view(&heap_locs);
-
-                let stdin  = stdin();
-                let mut stdout = stdout().into_raw_mode().unwrap();
-
-                write!(stdout, "{}\n\r", bindings).unwrap();
-                stdout.flush().unwrap();
-
-                if !wam.or_stack_is_empty() {
-                    write!(stdout, "Press ; to continue or A to abort.\n\r").unwrap();
-                    stdout.flush().unwrap();
-
-                    for c in stdin.keys() {
-                        match c.unwrap() {
-                            Key::Char(';') => {
-                                result = wam.continue_query();
-                                break;
-                            },
-                            Key::Char('a') | Key::Char('A') =>
-                                break 'outer,
-                            _ => {}
-                        }
-                    };
-
-                    if let &EvalResult::QueryFailure = &result {
-                        write!(stdout, "no\n\r").unwrap();
-                        stdout.flush().unwrap();
-                        break;
-                    }
-                } else {
-                    break;
-                }
-            }
-        },
-        EvalResult::QueryFailure => println!("no"),
-        _ => {}
-    };
-}

src/l3/iterators.rs

@@ -1,175 +0,0 @@
-use l3::ast::*;
-
-use std::cell::Cell;
-use std::collections::VecDeque;
-use std::vec::Vec;
-
-enum IteratorState<'a> {
-    Atom(Level, &'a Cell<RegType>, &'a Atom),
-    Clause(Level, usize, &'a Cell<RegType>, &'a Atom, &'a Vec<Box<Term>>),
-    IsolatedAtom(&'a Cell<RegType>, &'a Atom),
-    IsolatedVar(&'a Cell<VarReg>, &'a Var),
-    RootClause(usize, &'a Vec<Box<Term>>),
-    Var(Level, &'a Cell<VarReg>, &'a Var)
-}
-
-impl<'a> IteratorState<'a> {
-    fn to_state(lvl: Level, term: &'a Term) -> IteratorState<'a>
-    {
-        match term {
-            &Term::Atom(ref cell, ref atom) =>
-                IteratorState::Atom(lvl, cell, atom),
-            &Term::Clause(ref cell, ref atom, ref child_terms) =>
-                IteratorState::Clause(lvl, 0, cell, atom, child_terms),
-            &Term::Var(ref cell, ref var) =>
-                IteratorState::Var(lvl, cell, var)
-        }
-    }
-}
-
-pub struct QueryIterator<'a> {
-    state_stack: Vec<IteratorState<'a>>
-}
-
-impl<'a> QueryIterator<'a> {
-    fn push_clause(&mut self,
-                   lvl: Level,
-                   child_num: usize,
-                   cell: &'a Cell<RegType>,
-                   name: &'a Atom,
-                   child_terms: &'a Vec<Box<Term>>)
-    {
-        self.state_stack.push(IteratorState::Clause(lvl,
-                                                    child_num,
-                                                    cell,
-                                                    name,
-                                                    child_terms));
-    }
-
-    fn push_root_clause(&mut self,
-                        child_num: usize,
-                        child_terms: &'a Vec<Box<Term>>)
-    {
-        self.state_stack.push(IteratorState::RootClause(child_num, child_terms));
-    }
-
-    fn push_subterm(&mut self, lvl: Level, term: &'a Term) {
-        self.state_stack.push(IteratorState::to_state(lvl, term));
-    }
-
-    fn new(term: &'a Term) -> QueryIterator<'a> {
-        let state = match term {
-            &Term::Atom(ref cell, ref atom) =>
-                IteratorState::IsolatedAtom(cell, atom),
-            &Term::Clause(_, _, ref terms) =>
-                IteratorState::RootClause(0, terms),
-            &Term::Var(ref cell, ref var) =>
-                IteratorState::IsolatedVar(cell, var)
-        };
-
-        QueryIterator { state_stack: vec![state] }
-    }
-}
-
-impl<'a> Iterator for QueryIterator<'a> {
-    type Item = TermRef<'a>;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        while let Some(iter_state) = self.state_stack.pop() {
-            match iter_state {
-                IteratorState::Atom(lvl, cell, atom) =>
-                    return Some(TermRef::Atom(lvl, cell, atom)),
-                IteratorState::Clause(lvl, child_num, cell, atom, child_terms) => {
-                    if child_num == child_terms.len() {
-                        return Some(TermRef::Clause(lvl, cell, atom, child_terms));
-                    } else {
-                        self.push_clause(lvl, child_num + 1, cell, atom, child_terms);
-                        self.push_subterm(Level::Deep, child_terms[child_num].as_ref());
-                    }
-                },
-                IteratorState::IsolatedAtom(cell, atom) =>
-                    return Some(TermRef::Atom(Level::Shallow, cell, atom)),
-                IteratorState::IsolatedVar(cell, var) =>
-                    return Some(TermRef::Var(Level::Shallow, cell, var)),
-                IteratorState::RootClause(child_num, child_terms) => {
-                    if child_num == child_terms.len() {
-                        return None;
-                    } else {
-                        self.push_root_clause(child_num + 1, child_terms);
-                        self.push_subterm(Level::Shallow, child_terms[child_num].as_ref());
-                    }
-                },
-                IteratorState::Var(lvl, cell, var) =>
-                    return Some(TermRef::Var(lvl, cell, var))
-            };
-        }
-
-        None
-    }
-}
-
-pub struct FactIterator<'a> {
-    state_queue: VecDeque<IteratorState<'a>>,
-}
-
-impl<'a> FactIterator<'a> {
-    fn push_subterm(&mut self, lvl: Level, term: &'a Term) {
-        self.state_queue.push_back(IteratorState::to_state(lvl, term));
-    }
-
-    fn new(term: &'a Term) -> FactIterator<'a> {
-        let states = match term {
-            &Term::Atom(ref cell, ref atom) =>
-                vec![IteratorState::IsolatedAtom(cell, atom)],
-            &Term::Clause(_, _, ref terms) =>
-                vec![IteratorState::RootClause(0, terms)],
-            &Term::Var(ref cell, ref var) =>
-                vec![IteratorState::IsolatedVar(cell, var)]
-        };
-
-        FactIterator { state_queue:  VecDeque::from(states) }
-    }
-}
-
-impl<'a> Iterator for FactIterator<'a> {
-    type Item = TermRef<'a>;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        while let Some(state) = self.state_queue.pop_front() {
-            match state {
-                IteratorState::Atom(lvl, cell, atom) =>
-                    return Some(TermRef::Atom(lvl, cell, atom)),
-                IteratorState::Clause(lvl, _, cell, atom, child_terms) => {
-                    for child_term in child_terms {
-                        self.push_subterm(Level::Deep, child_term);
-                    }
-
-                    return Some(TermRef::Clause(lvl, cell, atom, child_terms));
-                },
-                IteratorState::IsolatedAtom(cell, atom) =>
-                    return Some(TermRef::Atom(Level::Shallow, cell, atom)),
-                IteratorState::IsolatedVar(cell, var) =>
-                    return Some(TermRef::Var(Level::Shallow, cell, var)),
-                IteratorState::RootClause(_, child_terms) => {
-                    for child_term in child_terms {
-                        self.push_subterm(Level::Shallow, child_term);
-                    }
-                },
-                IteratorState::Var(lvl, cell, var) =>
-                    return Some(TermRef::Var(lvl, cell, var))
-            }
-        }
-
-        None
-    }
-}
-
-impl Term {
-    pub fn post_order_iter(&self) -> QueryIterator {
-        QueryIterator::new(self)
-    }
-
-    pub fn breadth_first_iter(&self) -> FactIterator {
-        FactIterator::new(self)
-    }
-}

src/l3/l3_parser.lalrpop

@@ -1,59 +0,0 @@
-use l3::ast::*;
-
-use std::cell::Cell;
-
-grammar;
-
-pub TopLevel: TopLevel = {
-    "?-" <t:Term> "." => TopLevel::Query(t),
-    <Predicate> => TopLevel::Predicate(<>),
-    <Rule>  "." => TopLevel::Rule(<>),
-    <Term>  "." => TopLevel::Fact(<>)    
-};
-
-Atom : Atom = {
-    r"[a-z][a-z0-9_]*" => <>.trim().to_string(),
-};
-
-BoxedTerm : Box<Term> = {
-    <t:Term> => Box::new(t)
-};
-
-Clause : Term = {
-    <a:Atom> "(" <ts: (<BoxedTerm> ",")*> <t:BoxedTerm> ")" => {
-     	let mut ts = ts;
-     	ts.push(t);
-	Term::Clause(Cell::new(RegType::Temp(0)), a, ts)
-    }
-};
-
-Predicate : Vec<PredicateClause> = {
-    <pcs: (<PredicateClause>)+> <pc: PredicateClause> => {
-        let mut pcs = pcs;
-	pcs.push(pc);
-	pcs
-    }  
-};
-
-PredicateClause : PredicateClause = {
-    <Rule> "." => PredicateClause::Rule(<>),
-    <Term> "." => PredicateClause::Fact(<>)
-};
-
-Rule : Rule = {
-    <c:Clause> ":-" <h:Term> <cs: ("," <Term>)*> =>
-         Rule { head: (c, h), clauses: cs },
-    <a:Atom> ":-" <h:Term> <cs: ("," <Term>)*> =>
-         Rule { head: (Term::Atom(Cell::new(RegType::Temp(0)), a), h),
-	        clauses: cs }
-};
-
-Term : Term = {
-    <Clause> => <>,
-    <Atom>   => Term::Atom(Cell::new(RegType::Temp(0)), <>),
-    <Var>    => Term::Var(Cell::new(VarReg::Norm(RegType::Temp(0))), <>)
-};
-
-Var : Var = {
-    r"[A-Z][a-z0-9_]*" => <>.trim().to_string(),
-};

src/l3/machine.rs

@@ -1,677 +0,0 @@
-use l3::ast::*;
-use l3::codegen::*;
-use l3::heapview::*;
-use l3::and_stack::*;
-use l3::or_stack::*;
-
-use std::collections::HashMap;
-use std::ops::{Index, IndexMut};
-use std::vec::Vec;
-
-#[derive(Clone, Copy)]
-enum MachineMode {
-    Read,
-    Write
-}
-
-struct MachineState {
-    h: usize,
-    s: usize,
-    p: CodePtr,
-    b: usize,
-    e: usize,
-    num_of_args: usize,
-    cp: CodePtr,
-    fail: bool,
-    heap: Heap,
-    mode: MachineMode,
-    and_stack: AndStack,
-    or_stack: OrStack,
-    registers: Registers,
-    trail: Vec<Ref>,
-    tr: usize,
-    hb: usize
-}
-
-type CodeDir = HashMap<(Atom, usize), usize>;
-
-impl Index<RegType> for MachineState {
-    type Output = Addr;
-
-    fn index(&self, reg: RegType) -> &Self::Output {
-        match reg {
-            RegType::Temp(temp) => &self.registers[temp],
-            RegType::Perm(perm) => {
-                let e = self.e;
-                &self.and_stack[e][perm]
-            }
-        }
-    }
-}
-
-impl IndexMut<RegType> for MachineState {
-    fn index_mut(&mut self, reg: RegType) -> &mut Self::Output {
-        match reg {
-            RegType::Temp(temp) => &mut self.registers[temp],
-            RegType::Perm(perm) => {
-                let e = self.e;
-                &mut self.and_stack[e][perm]
-            }
-        }
-    }
-}
-
-pub struct Machine {
-    ms: MachineState,
-    code: Code,
-    code_dir: CodeDir
-}
-
-impl Machine {
-    pub fn new() -> Self {
-        Machine {
-            ms: MachineState::new(),
-            code: Vec::new(),
-            code_dir: HashMap::new()
-        }
-    }
-
-    pub fn failed(&self) -> bool {
-        self.ms.fail
-    }
-
-    pub fn add_fact(&mut self, fact: &Term, mut code: Code) {
-        let p = self.code.len();
-        let name  = fact.name().clone();
-        let arity = fact.arity();
-
-        self.code.append(&mut code);
-        self.code_dir.insert((name, arity), p);
-    }
-
-    pub fn add_rule(&mut self, rule: &Rule, mut code: Code) {
-        let p = self.code.len();
-        let name  = rule.head.0.name().clone();
-        let arity = rule.head.0.arity();
-
-        self.code.append(&mut code);
-        self.code_dir.insert((name, arity), p);
-    }
-
-    pub fn add_predicate(&mut self, pred: &Vec<PredicateClause>, mut code: Code)
-    {
-        let p = self.code.len();
-        let name  = pred.first().unwrap().name().clone();
-        let arity = pred.first().unwrap().arity();
-
-        self.code.append(&mut code);
-        self.code_dir.insert((name, arity), p);
-    }
-
-    fn execute_instr<'a>(&mut self, instr_src: LineOrCodeOffset<'a>) -> bool
-    {
-        let mut instr = match instr_src {
-            LineOrCodeOffset::Instruction(instr) => instr,
-            LineOrCodeOffset::Offset(p) => &self.code[p]
-        };
-
-        loop {
-            match instr {
-                &Line::Choice(ref choice_instr) =>
-                    self.ms.execute_choice_instr(choice_instr),
-                &Line::Fact(ref fact) => {
-                    for fact_instr in fact {
-                        self.ms.execute_fact_instr(&fact_instr);
-                    }
-                    self.ms.p += 1;
-                },
-                &Line::Query(ref query) => {
-                    for query_instr in query {
-                        self.ms.execute_query_instr(&query_instr);
-                    }
-                    self.ms.p += 1;
-                },
-                &Line::Control(ref control_instr) =>
-                    self.ms.execute_ctrl_instr(&self.code_dir, control_instr),
-            }
-
-            if self.failed() {
-                let p = self.ms
-                            .or_stack
-                            .top()
-                            .map(|fr| fr.bp)
-                            .unwrap_or_default();
-
-                if let CodePtr::TopLevel = p {
-                    return false;
-                } else {
-                    self.ms.fail = false;
-                    self.ms.p = p;
-                }
-            }
-
-            match self.ms.p {
-                CodePtr::DirEntry(p) if p < self.code.len() =>
-                    instr = &self.code[p],
-                _ => break
-            }
-        }
-
-        true
-    }
-
-    pub fn heap_view(&self, var_dir: &HeapVarDict) -> String {
-        let mut result = String::new();
-
-        for (var, addr) in var_dir {
-            let mut arities = Vec::new();
-            let viewer = HeapCellViewer::new(&self.ms.heap,
-                                             &self.ms.and_stack,
-                                             *addr);
-
-            if result != "" {
-                result += "\n\r";
-            }
-
-            result += var.as_str();
-            result += " = ";
-
-            for view in viewer {
-                match arities.pop() {
-                    Some(n) => arities.push(n-1),
-                    None => {}
-                }
-
-                if !(arities.is_empty() || result.ends_with("(")) {
-                    result += ", ";
-                }
-
-                match view {
-                    HeapCellView::Str(arity, ref name) => {
-                        result += name.as_str();
-
-                        if arity > 0 {
-                            arities.push(arity);
-                            result += "(";
-                        }
-                    },
-                    HeapCellView::HeapVar(cell_num) => {
-                        result += "_";
-                        result += cell_num.to_string().as_str();
-                    },
-                    HeapCellView::StackVar(fr, sc) => {
-                        result += "_s_";
-                        result += fr.to_string().as_str();
-                        result += "_";
-                        result += sc.to_string().as_str();
-                    }
-                }
-
-                while let Some(&0) = arities.last() {
-                    result += ")";
-                    arities.pop();
-                }
-            }
-        }
-
-        result
-    }
-
-    pub fn run_query(&mut self, code: Code, cg: &CodeGenerator) -> EvalResult
-    {
-        let mut succeeded = true;
-        let mut heap_locs = HashMap::new();
-
-        for instr in code.iter().take(1) {
-            succeeded = self.execute_instr(LineOrCodeOffset::from(instr));
-        }
-
-        if succeeded {
-            for (var, vr) in cg.vars() {
-                let addr = self.ms.registers[vr.root_register()];
-                heap_locs.insert((*var).clone(), addr);
-            }
-
-            for instr in code.iter().skip(1) {
-                succeeded = self.execute_instr(LineOrCodeOffset::from(instr));
-                if !succeeded {
-                    break;
-                }
-            }
-        }
-
-        if succeeded {
-            EvalResult::InitialQuerySuccess(heap_locs)
-        } else {
-            EvalResult::QueryFailure
-        }
-    }
-
-    pub fn or_stack_is_empty(&self) -> bool {
-        self.ms.or_stack.is_empty()
-    }
-
-    pub fn continue_query(&mut self) -> EvalResult
-    {
-        if !self.or_stack_is_empty() {
-            let b = self.ms.b;
-            self.ms.p = self.ms.or_stack[b].bp;
-
-            let succeeded = if let CodePtr::DirEntry(p) = self.ms.p {
-                self.execute_instr(LineOrCodeOffset::Offset(p))
-            } else {
-                false
-            };
-
-            if succeeded {
-                EvalResult::SubsequentQuerySuccess
-            } else {
-                EvalResult::QueryFailure
-            }
-        } else {
-            EvalResult::QueryFailure
-        }
-    }
-
-    pub fn reset(&mut self) {
-        self.ms.reset();
-    }
-}
-
-impl MachineState {
-    fn new() -> MachineState {
-        MachineState { h: 0,
-                       s: 0,
-                       p: CodePtr::TopLevel,
-                       b: 0,
-                       e: 0,
-                       num_of_args: 0,
-                       cp: CodePtr::TopLevel,
-                       fail: false,
-                       heap: Vec::with_capacity(256),
-                       mode: MachineMode::Write,
-                       and_stack: AndStack::new(),
-                       or_stack: OrStack::new(),
-                       registers: vec![Addr::HeapCell(0); 32],
-                       trail: Vec::new(),
-                       tr: 0,
-                       hb: 0
-        }
-    }
-
-    fn num_frames(&self) -> usize {
-        self.and_stack.len() + self.or_stack.len()
-    }
-
-    fn store(&self, a: Addr) -> Addr {
-        match a {
-            Addr::HeapCell(r)       => self.heap[r].as_addr(r),
-            Addr::StackCell(fr, sc) => self.and_stack[fr][sc],
-            addr                    => addr
-        }
-    }
-
-    fn deref(&self, a: Addr) -> Addr {
-        let mut a = a;
-
-        loop {
-            let value = self.store(a);
-
-            if value.is_ref() && value != a {
-                a = value;
-                continue;
-            }
-
-            return a;
-        };
-    }
-
-    fn bind(&mut self, r1: Ref, a2: Addr) {
-        let t2 = self.store(a2);
-
-        match r1 {
-            Ref::StackCell(fr, sc) =>
-                self.and_stack[fr][sc] = t2,
-            Ref::HeapCell(hc) =>
-                self.heap[hc] = HeapCellValue::from(t2)
-        };
-
-        self.trail(r1);
-    }
-
-    fn unify(&mut self, a1: Addr, a2: Addr) {
-        let mut pdl = vec![a1, a2];
-
-        self.fail = false;
-
-        while !(pdl.is_empty() || self.fail) {
-            let d1 = self.deref(pdl.pop().unwrap());
-            let d2 = self.deref(pdl.pop().unwrap());
-
-            if d1 != d2 {
-                match (self.store(d1), self.store(d2)) {
-                    (Addr::HeapCell(hc), _) =>
-                        self.bind(Ref::HeapCell(hc), d2),
-                    (_, Addr::HeapCell(hc)) =>
-                        self.bind(Ref::HeapCell(hc), d1),
-                    (Addr::StackCell(fr, sc), _) =>
-                        self.bind(Ref::StackCell(fr, sc), d2),
-                    (_, Addr::StackCell(fr, sc)) =>
-                        self.bind(Ref::StackCell(fr, sc), d1),
-                    (Addr::Str(a1), Addr::Str(a2)) => {
-                        let r1 = &self.heap[a1];
-                        let r2 = &self.heap[a2];
-
-                        if let &HeapCellValue::NamedStr(n1, ref f1) = r1 {
-                            if let &HeapCellValue::NamedStr(n2, ref f2) = r2 {
-                                if n1 == n2 && *f1 == *f2 {
-                                    for i in 1 .. n1 + 1 {
-                                        pdl.push(Addr::HeapCell(a1 + i));
-                                        pdl.push(Addr::HeapCell(a2 + i));
-                                    }
-
-                                    continue;
-                                }
-                            }
-                        }
-
-                        self.fail = true;
-                    }
-                };
-            }
-        }
-    }
-
-    fn trail(&mut self, r: Ref) {
-        match r {
-            Ref::HeapCell(hc) => {
-                if hc < self.hb {
-                    self.trail.push(r);
-                    self.tr += 1;
-                }
-            },
-            Ref::StackCell(fr, _) => {
-                let fr_gi = self.and_stack[fr].global_index;
-                let b_gi  = if !self.or_stack.is_empty() {
-                    self.or_stack[self.b].global_index
-                } else {
-                    0
-                };
-
-                if fr_gi < b_gi {
-                    self.trail.push(r);
-                    self.tr += 1;
-                }
-            }
-        }
-    }
-
-    fn unwind_trail(&mut self, a1: usize, a2: usize) {
-        for i in a1 .. a2 {
-            match self.trail[i] {
-                Ref::HeapCell(r) =>
-                    self.heap[r] = HeapCellValue::Ref(self.trail[i]),
-                Ref::StackCell(fr, sc) =>
-                    self.and_stack[fr][sc] = Addr::StackCell(fr, sc)
-            }
-        }
-    }
-
-    fn execute_query_instr(&mut self, instr: &QueryInstruction) {
-        match instr {
-            &QueryInstruction::PutStructure(_, ref name, arity, reg) => {
-                self.heap.push(HeapCellValue::Str(self.h + 1));
-                self.heap.push(HeapCellValue::NamedStr(arity, name.clone()));
-
-                self[reg] = Addr::Str(self.h + 1);
-
-                self.h += 2;
-            },
-            &QueryInstruction::PutValue(norm, arg) =>
-                self.registers[arg] = self[norm],
-            &QueryInstruction::PutVariable(norm, arg) => {
-                self.heap.push(HeapCellValue::Ref(Ref::HeapCell(self.h)));
-
-                self[norm] = Addr::HeapCell(self.h);
-                self.registers[arg] = Addr::HeapCell(self.h);
-
-                self.h += 1;
-            },
-            &QueryInstruction::SetVariable(reg) => {
-                self.heap.push(HeapCellValue::Ref(Ref::HeapCell(self.h)));
-                self[reg] = Addr::HeapCell(self.h);
-
-                self.h += 1;
-            },
-            &QueryInstruction::SetValue(reg) => {
-                let heap_val = self[reg];
-                self.heap.push(HeapCellValue::from(heap_val));
-
-                self.h += 1;
-            },
-        }
-    }
-
-    fn execute_fact_instr(&mut self, instr: &FactInstruction) {
-        match instr {
-            &FactInstruction::GetStructure(_, ref name, arity, reg) => {
-                let addr = self.deref(self[reg]);
-
-                match self.store(addr) {
-                    Addr::Str(a) => {
-                        let result = &self.heap[a];
-
-                        if let &HeapCellValue::NamedStr(narity, ref str) = result {
-                            if narity == arity && *name == *str {
-                                self.s = a + 1;
-                                self.mode = MachineMode::Read;
-                            } else {
-                                self.fail = true;
-                            }
-                        }
-                    },
-                    Addr::HeapCell(_) | Addr::StackCell(_, _) => {
-                        self.heap.push(HeapCellValue::Str(self.h + 1));
-                        self.heap.push(HeapCellValue::NamedStr(arity, name.clone()));
-
-                        let h = self.h;
-
-                        self.bind(addr.as_ref().unwrap(), Addr::HeapCell(h));
-
-                        self.h += 2;
-                        self.mode = MachineMode::Write;
-                    }
-                };
-            },
-            &FactInstruction::GetVariable(norm, arg) =>
-                self[norm] = self.registers[arg],
-            &FactInstruction::GetValue(norm, arg) => {
-                let norm_addr = self[norm];
-                let reg_addr  = self.registers[arg];
-
-                self.unify(norm_addr, reg_addr);
-            },
-            &FactInstruction::UnifyVariable(reg) => {
-                match self.mode {
-                    MachineMode::Read  =>
-                        self[reg] = self.heap[self.s].as_addr(self.s),
-                    MachineMode::Write => {
-                        self.heap.push(HeapCellValue::Ref(Ref::HeapCell(self.h)));
-                        self[reg] = Addr::HeapCell(self.h);
-                        self.h += 1;
-                    }
-                };
-
-                self.s += 1;
-            },
-            &FactInstruction::UnifyValue(reg) => {
-                let s = self.s;
-
-                match self.mode {
-                    MachineMode::Read  => {
-                        let reg_addr = self[reg];
-                        self.unify(reg_addr, Addr::HeapCell(s));
-                    },
-                    MachineMode::Write => {
-                        let heap_val = self.store(self[reg]);
-                        self.heap.push(HeapCellValue::from(heap_val));
-                        self.h += 1;
-                    }
-                };
-
-                self.s += 1;
-            }
-        };
-    }
-
-    fn execute_ctrl_instr(&mut self, code_dir: &CodeDir, instr: &ControlInstruction)
-    {
-        match instr {
-            &ControlInstruction::Allocate(num_cells) => {
-                let num_frames = self.num_frames();
-
-                self.and_stack.push(num_frames + 1, self.e, self.cp, num_cells);
-
-                self.e = self.and_stack.len() - 1;
-                self.p += 1;
-            },
-            &ControlInstruction::Call(ref name, arity) => {
-                let compiled_tl_index = code_dir.get(&(name.clone(), arity))
-                                                .map(|index| *index);
-
-                match compiled_tl_index {
-                    Some(compiled_tl_index) => {
-                        self.cp = self.p + 1;
-                        self.num_of_args = arity;
-                        self.p  = CodePtr::DirEntry(compiled_tl_index);
-                    },
-                    None => self.fail = true
-                };
-            },
-            &ControlInstruction::Deallocate => {
-                let e = self.e;
-
-                let num_frame_e = self.and_stack.top().unwrap().global_index;
-                let num_frame_b = self.or_stack
-                                      .top()
-                                      .map(|fr| fr.global_index)
-                                      .unwrap_or(0);
-
-                self.p = self.and_stack[e].cp;
-                self.e = self.and_stack[e].e;
-
-                if num_frame_e > num_frame_b {
-                    let top_e = self.and_stack.top().unwrap().e;
-                    self.and_stack.drop_frames(top_e - self.e + 1);
-                }
-            },
-            &ControlInstruction::Proceed =>
-                self.p = self.cp,
-        };
-    }
-
-    fn execute_choice_instr(&mut self, instr: &ChoiceInstruction)
-    {
-        match instr {
-            &ChoiceInstruction::TryMeElse(offset) => {
-                let n = self.num_of_args;
-                let num_frames = self.num_frames();
-
-                self.or_stack.push(num_frames + 1,
-                                   self.e,
-                                   self.cp,
-                                   self.b,
-                                   self.p + offset,
-                                   self.tr,
-                                   self.h,
-                                   self.num_of_args);
-
-                self.b = self.or_stack.len() - 1;
-                let b = self.b;
-
-                for i in 1 .. n + 1 {
-                    self.or_stack[b][i] = self.registers[i];
-                }
-
-                self.hb = self.h;
-                self.p += 1;
-            },
-            &ChoiceInstruction::RetryMeElse(offset) => {
-                let b = self.b;
-                let n = self.or_stack[b].num_args();
-
-                for i in 1 .. n + 1 {
-                    self.registers[i] = self.or_stack[b][i];
-                }
-
-                self.e = self.or_stack[b].e;
-                self.cp = self.or_stack[b].cp;
-
-                self.or_stack[b].bp = self.p + offset;
-
-                let old_tr  = self.or_stack[b].tr;
-                let curr_tr = self.tr;
-
-                self.unwind_trail(old_tr, curr_tr);
-                self.tr = self.or_stack[b].tr;
-
-                self.trail.truncate(self.tr);
-                self.heap.truncate(self.or_stack[b].h);
-
-                self.h  = self.or_stack[b].h;
-                self.hb = self.h;
-
-                self.p += 1;
-            },
-            &ChoiceInstruction::TrustMe => {
-                let b = self.b;
-                let n = self.or_stack[b].num_args();
-
-                for i in 1 .. n + 1 {
-                    self.registers[i] = self.or_stack[b][i];
-                }
-
-                self.e  = self.or_stack[b].e;
-                self.cp = self.or_stack[b].cp;
-
-                let old_tr  = self.or_stack[b].tr;
-                let curr_tr = self.tr;
-
-                self.unwind_trail(old_tr, curr_tr);
-
-                self.tr = self.or_stack[b].tr;
-                self.trail.truncate(self.tr);
-
-                self.h = self.or_stack[b].h;
-                self.heap.truncate(self.h);
-
-                self.b = self.or_stack[b].b;
-
-                self.or_stack.pop();
-
-                self.hb = self.h;
-                self.p += 1;
-            }
-        }
-    }
-
-    fn reset(&mut self) {
-        self.h = 0;
-        self.hb = 0;
-        self.e = 0;
-        self.b = 0;
-        self.s = 0;
-        self.tr = 0;
-        self.p = CodePtr::TopLevel;
-        self.cp = CodePtr::TopLevel;
-        self.num_of_args = 0;
-
-        self.fail = false;
-        self.trail.clear();
-        self.heap.clear();
-        self.mode = MachineMode::Write;
-        self.and_stack.clear();
-        self.or_stack.clear();
-        self.registers = vec![Addr::HeapCell(0); 32];
-    }
-}

src/l3/mod.rs

@@ -1,9 +0,0 @@
-pub mod and_stack;
-pub mod ast;
-pub mod codegen;
-pub mod heapview;
-pub mod io;
-pub mod iterators;
-pub mod l3_parser;
-pub mod machine;
-pub mod or_stack;

src/l3/or_stack.rs

@@ -1,112 +0,0 @@
-use l3::ast::*;
-
-use std::ops::{Index, IndexMut};
-use std::vec::Vec;
-
-pub struct Frame {
-    pub global_index: usize,
-    pub e: usize,
-    pub cp: CodePtr,
-    pub b: usize,
-    pub bp: CodePtr,
-    pub tr: usize,
-    pub h: usize,
-    args: Vec<Addr>
-}
-
-impl Frame {
-    fn new(global_index: usize,
-           e: usize,
-           cp: CodePtr,
-           b: usize,
-           bp: CodePtr,
-           tr: usize,
-           h: usize,
-           n: usize)
-           -> Self
-    {
-        Frame {
-            global_index: global_index,
-            e: e,
-            cp: cp,
-            b: b,
-            bp: bp,
-            tr: tr,
-            h: h,
-            args: vec![Addr::HeapCell(0); n]
-        }
-    }
-
-    pub fn num_args(&self) -> usize {
-        self.args.len()
-    }
-}
-
-pub struct OrStack(Vec<Frame>);
-
-impl OrStack {
-    pub fn new() -> Self {
-        OrStack(Vec::new())
-    }
-
-    pub fn push(&mut self,
-                global_index: usize,
-                e: usize,
-                cp: CodePtr,
-                b: usize,
-                bp: CodePtr,
-                tr: usize,
-                h: usize,
-                n: usize)
-    {
-        self.0.push(Frame::new(global_index, e, cp, b, bp, tr, h, n));
-    }
-
-    pub fn len(&self) -> usize {
-        self.0.len()
-    }
-
-    pub fn clear(&mut self) {
-        self.0.clear()
-    }
-
-    pub fn top(&self) -> Option<&Frame> {
-        self.0.last()
-    }
-
-    pub fn pop(&mut self) {
-        self.0.pop();
-    }
-
-    pub fn is_empty(&self) -> bool {
-        self.0.is_empty()
-    }
-}
-
-impl Index<usize> for OrStack {
-    type Output = Frame;
-
-    fn index(&self, index: usize) -> &Self::Output {
-        self.0.index(index)
-    }
-}
-
-impl IndexMut<usize> for OrStack {
-    fn index_mut(&mut self, index: usize) -> &mut Self::Output {
-        self.0.index_mut(index)
-    }
-}
-
-impl Index<usize> for Frame {
-    type Output = Addr;
-
-    fn index(&self, index: usize) -> &Self::Output {
-        self.args.index(index - 1)
-    }
-}
-
-impl IndexMut<usize> for Frame {
-    fn index_mut(&mut self, index: usize) -> &mut Self::Output {
-        self.args.index_mut(index - 1)
-    }
-}

src/lib/arithmetic.pl

@@ -0,0 +1,123 @@
+:- module(arithmetic, [expmod/4, lsb/2, msb/2, number_to_rational/2,
+                       number_to_rational/3,
+                       rational_numerator_denominator/3]).
+
+:- use_module(library(charsio), [write_term_to_chars/3]).
+:- use_module(library(error)).
+:- use_module(library(lists), [append/3, member/2]).
+
+expmod(Base, Expo, Mod, R) :-
+    (   member(N, [Base, Expo, Mod]), var(N) -> instantiation_error(expmod/4)
+    ;   member(N, [Base, Expo, Mod]), \+ integer(N) ->
+        type_error(integer, N, expmod/4)
+    ;   Expo < 0 -> domain_error(not_less_than_zero, Expo, expmod/4)
+    ;   expmod_(Base, Expo, Mod, 1, R)
+    ).
+
+expmod_(_, _, 1, _, 0) :- !.
+expmod_(_, 0, _, R, R) :- !.
+expmod_(Base0, Expo0, Mod, C0, R) :-
+    Expo0 /\ 1 =:= 1,
+    C is (C0 * Base0) mod Mod,
+    !,
+    Expo is Expo0 >> 1,
+    Base is (Base0 * Base0) mod Mod,
+    expmod_(Base, Expo, Mod, C, R).
+expmod_(Base0, Expo0, Mod, C, R) :-
+    Expo is Expo0 >> 1,
+    Base is (Base0 * Base0) mod Mod,
+    expmod_(Base, Expo, Mod, C, R).
+
+lsb(X, N) :-
+    builtins:must_be_number(X, lsb/2),
+    (   \+ integer(X) -> type_error(integer, X, lsb/2)
+    ;   X < 1 -> domain_error(not_less_than_one, X, lsb/2)
+    ;   builtins:can_be_number(N, lsb/2),
+        X1 is X /\ (-X),
+        msb_(X1, -1, N)
+    ).
+
+msb(X, N) :-
+    builtins:must_be_number(X, msb/2),
+    (   \+ integer(X) -> type_error(integer, X, msb/2)
+    ;   X < 1 -> domain_error(not_less_than_one, X, msb/2)
+    ;   builtins:can_be_number(N, msb/2),
+        X1 is X >> 1,
+        msb_(X1, 0, N)
+    ).
+
+msb_(0, N, N) :- !.
+msb_(X, M, N) :-
+    X1 is X >> 1,
+    M1 is M + 1,
+    msb_(X1, M1, N).
+
+number_to_rational(Real, Fraction) :-
+    (   var(Real) -> instantiation_error(number_to_rational/2)
+    ;   integer(Real) -> Fraction is Real rdiv 1
+    ;   (rational(Real) ; float(Real)) ->
+            number_to_rational(1.0e-6, Real, Fraction)
+    ;   type_error(number, Real, number_to_rational/2)
+    ).
+
+% If 0 <= Eps0 <= 1e-16 then the search is for "infinite" precision.
+number_to_rational(Eps0, Real0, Fraction) :-
+    (   var(Eps0) -> instantiation_error(number_to_rational/3)
+    ;   \+ number(Eps0) -> type_error(number, Eps0, number_to_rational/3)
+    ;   Eps0 < 0 -> domain_error(not_less_than_zero, Eps0, number_to_rational/3)
+    ;   Eps_ is Eps0 rdiv 1,
+        rational_numerator_denominator(Eps_, EpsN, EpsD),
+        Eps = EpsN/EpsD
+    ),
+    (   var(Real0) -> instantiation_error(number_to_rational/3)
+    ;   \+ number(Real0) -> type_error(number, Eps0, number_to_rational/3)
+    ;   Real_ is Real0 rdiv 1,
+        rational_numerator_denominator(Real_, RealN, RealD),
+        Real = RealN/RealD
+    ),
+    E0/E1 = Eps,
+    P0/Q0 = Real,
+    (   P0 < 0 -> I1 is -1 + P0 // Q0
+    ;   I1 is P0 // Q0
+    ),
+    P1 is P0 mod Q0,
+    Q1 = Q0,
+    (   P1 =:= 0 -> Fraction is I1 + 0 rdiv 1
+    ;   Qn1n is max(P1 * E1 - Q1 * E0, 0),
+        Qn1d is Q1 * E1,
+        Qn1 = Qn1n/Qn1d,
+        Qp1n is P1 * E1 + Q1 * E0,
+        Qp1d = Qn1d,
+        Qp1 = Qp1n/Qp1d,
+        stern_brocot_(Qn1, Qp1, 0/1, 1/0, P2/Q2),
+        Fraction is I1 + P2 rdiv Q2
+    ),
+    !.
+
+number(X) :-
+    (   integer(X)
+    ;   float(X)
+    ;   rational(X)
+    ).
+
+stern_brocot_(Qnn/Qnd, Qpn/Qpd, A/B, C/D, Fraction) :-
+    Fn1 is A + C,
+    Fd1 is B + D,
+    simplify_fraction(Fn1/Fd1, Fn/Fd),
+    S1 is sign(Fn * Qnd - Fd * Qnn),
+    S2 is sign(Fn * Qpd - Fd * Qpn),
+    (   S1 < 0 -> stern_brocot_(Qnn/Qnd, Qpn/Qpd, Fn/Fd, C/D, Fraction)
+    ;   S2 > 0 -> stern_brocot_(Qnn/Qnd, Qpn/Qpd, A/B, Fn/Fd, Fraction)
+    ;   Fraction = Fn/Fd
+    ).
+
+simplify_fraction(A0/B0, A/B) :-
+    G is gcd(A0, B0),
+    A is A0 // G,
+    B is B0 // G.
+
+rational_numerator_denominator(R, N, D) :-
+    write_term_to_chars(R, [], Cs),
+    append(Ns, [' ', r, d, i, v, ' '|Ds], Cs),
+    number_chars(N, Ns),
+    number_chars(D, Ds).

src/lib/assoc.pl

@@ -63,12 +63,12 @@ Assocs are Key-Value associations implemented as  a balanced binary tree
 @author         R.A.O'Keefe, L.Damas, V.S.Costa and Jan Wielemaker
 */
 
-/*					  
+/*
 :- meta_predicate
     map_assoc(1, ?),
     map_assoc(2, ?, ?).
 */
-					  
+
 %!  empty_assoc(?Assoc) is semidet.
 %
 %   Is true if Assoc is the empty association list.

src/lib/atts.pl

@@ -1,14 +1,14 @@
-:- module(atts, [attribute/1, call_residue_vars/2, '$absent_attr'/2,
-		 '$copy_attr_list'/2, '$get_attr'/2, '$put_attr'/2,
-		 '$absent_from_list'/2, '$get_from_list'/3,
-		 '$add_to_list'/3, '$del_attr'/3, '$del_attr_step'/3,
-		 '$del_attr_buried'/4, '$default_attr_list'/4]).
+:- module(atts, [op(1199, fx, attribute), call_residue_vars/2,
+                 term_attributed_variables/2,
+		         '$absent_attr'/2, '$copy_attr_list'/2, '$get_attr'/2,
+		         '$put_attr'/2, '$absent_from_list'/2,
+		         '$get_from_list'/3, '$add_to_list'/3, '$del_attr'/3,
+		         '$del_attr_step'/3, '$del_attr_buried'/4,
+		         '$default_attr_list'/4]).
 
 :- use_module(library(dcgs)).
 :- use_module(library(terms)).
 
-:- op(1199, fx, attribute).
-
 /* represent the list of attributes belonging to a variable,
    of a particular module, as a list of terms of the form
    Module:put_atts(V, ListOfAtts). */
@@ -20,7 +20,7 @@
 
 '$default_attr_list'([PG | PGs], Module, AttrVar) -->
     (  { '$module_of'(Module, PG) } -> [Module:put_atts(AttrVar, PG)]
-    ;  true
+    ;  { true }
     ),
     '$default_attr_list'(PGs, Module, AttrVar).
 '$default_attr_list'([], _, _) --> [].
@@ -29,26 +29,26 @@
     '$get_attr_list'(V, Ls),
     '$absent_from_list'(Ls, Attr).
 
-'$absent_from_list'(X, _) :-
-    var(X), !.
-'$absent_from_list'([L|Ls], Attr) :-
-    ( L \= Attr -> '$absent_from_list'(Ls, Attr) ).
+'$absent_from_list'(X, Attr) :-
+    (  var(X) -> true
+    ;  X = [L|Ls], L \= Attr -> '$absent_from_list'(Ls, Attr)
+    ).
 
 '$get_attr'(V, Attr) :-
     '$get_attr_list'(V, Ls), nonvar(Ls), '$get_from_list'(Ls, V, Attr).
 
 '$get_from_list'([L|Ls], V, Attr) :-
     nonvar(L),
-    ( L \= Attr -> nonvar(Ls), '$get_from_list'(Ls, V, Attr)
-    ; L = Attr -> '$enqueue_attr_var'(V)
-    ; '$get_from_list'(Ls, V, Attr)
+    (  L \= Attr -> nonvar(Ls), '$get_from_list'(Ls, V, Attr)
+    ;  L = Attr, '$enqueue_attr_var'(V)
     ).
 
 '$put_attr'(V, Attr) :-
     '$get_attr_list'(V, Ls), '$add_to_list'(Ls, V, Attr).
 
 '$add_to_list'(Ls, V, Attr) :-
-    ( var(Ls) -> Ls = [Attr | _], '$enqueue_attr_var'(V)
+    ( var(Ls) ->
+      Ls = [Attr | _], '$enqueue_attr_var'(V)
     ; Ls = [_ | Ls0], '$add_to_list'(Ls0, V, Attr)
     ).
 
@@ -57,26 +57,28 @@
 '$del_attr'(Ls0, V, Attr) :-
     Ls0 = [Att | Ls1],
     nonvar(Att),
-    ( Att \= Attr -> '$del_attr_buried'(Ls0, Ls1, V, Attr)
-    ; '$enqueue_attr_var'(V), '$del_attr_head'(V), '$del_attr'(Ls1, V, Attr)
+    (  Att \= Attr ->
+       '$del_attr_buried'(Ls0, Ls1, V, Attr)
+    ;  '$enqueue_attr_var'(V),
+       '$del_attr_head'(V),
+       '$del_attr'(Ls1, V, Attr)
     ).
 
 '$del_attr_step'(Ls1, V, Attr) :-
-    ( nonvar(Ls1) -> Ls1 = [_ | Ls2], '$del_attr_buried'(Ls1, Ls2, V, Attr)
-    ; true ).
+    (  nonvar(Ls1) -> Ls1 = [_ | Ls2], '$del_attr_buried'(Ls1, Ls2, V, Attr)
+    ;  true ).
 
 %% assumptions: Ls0 is a list, Ls1 is its tail;
 %%              the head of Ls0 can be ignored.
 '$del_attr_buried'(Ls0, Ls1, V, Attr) :-
-    Ls0 = [_, Att | _],
-    nonvar(Att),
-    !,
-    ( Att \= Attr -> '$del_attr_step'(Ls1, V, Attr)
-    ; '$enqueue_attr_var'(V),
-      '$del_attr_non_head'(Ls0), %% set tail of Ls0 = tail of Ls1. can be undone by backtracking.
-      '$del_attr_step'(Ls1, V, Attr)
+    (  var(Ls1) -> true
+    ;  Ls1 = [Att | Ls2] ->
+       (  Att \= Attr -> '$del_attr_buried'(Ls1, Ls2, V, Attr)
+       ;  '$enqueue_attr_var'(V),
+	  '$del_attr_non_head'(Ls0), %% set tail of Ls0 = tail of Ls1. can be undone by backtracking.
+	  '$del_attr_step'(Ls1, V, Attr)
+       )
     ).
-'$del_attr_buried'(_, _, _, _).
 
 '$copy_attr_list'(L, []) :- var(L), !.
 '$copy_attr_list'([Att|Atts], [Att|CopiedAtts]) :-
@@ -125,11 +127,19 @@ put_attr(Name, Arity) -->
     { functor(Attr, Name, Arity),
       numbervars(Attr, 0, Arity),
       V = '$VAR'(Arity) },
-    [(put_atts(V, +Attr) :- !, functor(Attr, Head, Arity), functor(AttrForm, Head, Arity),
-			    '$get_attr_list'(V, Ls), '$del_attr'(Ls, V, AttrForm), '$put_attr'(V, Attr)),
-     (put_atts(V,  Attr) :- !, functor(Attr, Head, Arity), functor(AttrForm, Head, Arity),
-			    '$get_attr_list'(V, Ls), '$del_attr'(Ls, V, AttrForm), '$put_attr'(V, Attr)),
-     (put_atts(V, -Attr) :- !, functor(Attr, _, _), '$get_attr_list'(V, Ls), '$del_attr'(Ls, V, Attr))].
+    [(put_atts(V, +Attr) :- !, functor(Attr, Head, Arity),
+			    functor(AttrForm, Head, Arity),
+			    '$get_attr_list'(V, Ls),
+			    '$del_attr'(Ls, V, AttrForm),
+			    '$put_attr'(V, Attr)),
+     (put_atts(V,  Attr) :- !, functor(Attr, Head, Arity),
+			    functor(AttrForm, Head, Arity),
+			    '$get_attr_list'(V, Ls),
+			    '$del_attr'(Ls, V, AttrForm),
+			    '$put_attr'(V, Attr)),
+     (put_atts(V, -Attr) :- !, functor(Attr, _, _),
+			    '$get_attr_list'(V, Ls),
+			    '$del_attr'(Ls, V, Attr))].
 
 get_attr(Name, Arity) -->
     { functor(Attr, Name, Arity),
@@ -150,3 +160,6 @@ call_residue_vars(Goal, Vars) :-
     '$get_attr_var_queue_delim'(B),
     call(Goal),
     '$get_attr_var_queue_beyond'(B, Vars).
+
+term_attributed_variables(Term, Vars) :-
+    '$term_attributed_variables'(Term, Vars).

src/lib/between.pl

@@ -9,7 +9,11 @@ between(Lower, Upper, X) :-
     must_be(integer, Lower),
     must_be(integer, Upper),
     can_be(integer, X),
-    between_(Lower, Upper, X).
+    (   nonvar(X) ->
+        Lower =< X,
+        X =< Upper
+    ;   between_(Lower, Upper, X)
+    ).
 
 between_(Lower, Upper, Lower) :-
     Lower =< Upper.

src/lib/builtins.pl

@@ -1,35 +1,19 @@
 :- op(400, yfx, /).
 
-/* this is an implementation specific declarative operator used to implement call_with_inference_limit/3
-   and setup_call_cleanup/3. switches to the default trust_me and retry_me_else. Indexing choice
-   instructions are unchanged. */
-:- op(700, fx, non_counted_backtracking).
-
-:- module(builtins, [(=)/2, (\=)/2, (\+)/1, (^)/2, (\)/1, (+)/1,
-	(+)/2, (**)/2, (*)/2, (-)/1, (-)/2, (/)/2, (/\)/2, (\/)/2,
-	(is)/2, (xor)/2, (div)/2, (//)/2, (rdiv)/2, (<<)/2, (>>)/2,
-	(mod)/2, (rem)/2, (>)/2, (<)/2, (=\=)/2, (=:=)/2, (>=)/2,
-	(=<)/2, (',')/2, (->)/2, (;)/2, (=..)/2, (==)/2, (\==)/2,
-	(@=<)/2, (@>=)/2, (@<)/2, (@>)/2, (:)/2, abolish/1, asserta/1,
-	assertz/1, atom_chars/2, atom_codes/2, atom_concat/3,
-	atom_length/2, bagof/3, catch/3, char_code/2, clause/2,
-	current_op/3, current_predicate/1, current_prolog_flag/2,
-	expand_goal/2, expand_term/2, fail/0, false/0, findall/3,
-	findall/4, get_char/1, halt/0, number_chars/2, number_codes/2,
-	once/1, op/3, read_term/2, repeat/0, retract/1,
-	set_prolog_flag/2, setof/3, sub_atom/5, subsumes_term/2,
-	term_variables/2, throw/1, true/0, unify_with_occurs_check/2,
-	write/1, write_canonical/1, write_term/2, writeq/1]).
-
 % module resolution operator.
 :- op(600, xfy, :).
 
 user:term_expansion((:- op(Pred, Spec, [Op | OtherOps])), OpResults) :-
-    expand_op_list([Op | OtherOps], Pred, Spec, OpResults).
+    '$expand_op_list'([Op | OtherOps], Pred, Spec, OpResults).
 
-expand_op_list([], _, _, []).
-expand_op_list([Op | OtherOps], Pred, Spec, [(:- op(Pred, Spec, Op)) | OtherResults]) :-
-    expand_op_list(OtherOps, Pred, Spec, OtherResults).
+'$expand_op_list'([], _, _, []).
+'$expand_op_list'([Op | OtherOps], Pred, Spec, [(:- op(Pred, Spec, Op)) | OtherResults]) :-
+    '$expand_op_list'(OtherOps, Pred, Spec, OtherResults).
+
+/* this is an implementation specific declarative operator used to implement call_with_inference_limit/3
+   and setup_call_cleanup/3. switches to the default trust_me and retry_me_else. Indexing choice
+   instructions are unchanged. */
+:- op(700, fx, non_counted_backtracking).
 
 % arithmetic operators.
 :- op(700, xfx, is).
@@ -37,19 +21,17 @@ expand_op_list([Op | OtherOps], Pred, Spec, [(:- op(Pred, Spec, Op)) | OtherResu
 :- op(400, yfx, *).
 :- op(200, xfy, [**, ^]).
 :- op(500, yfx, [/\, \/, xor]).
-:- op(400, yfx, [div, //, rdiv]).
-:- op(400, yfx, [<<, >>, mod, rem]).
+:- op(400, yfx, [div, //, rdiv, <<, >>, mod, rem]).
 :- op(200, fy, [+, -, \]).
 
+:- op(1200, xfx, -->).
+
 % arithmetic comparison operators.
 :- op(700, xfx, [>, <, =\=, =:=, >=, =<]).
 
 % term comparison.
 :- op(700, xfx, [==, \==, @=<, @>=, @<, @>]).
 
-% the maximum arity flag. needs to be replaced with current_prolog_flag(max_arity, MAX_ARITY).
-max_arity(255).
-
 % conditional operators.
 :- op(1050, xfy, ->).
 :- op(1100, xfy, ;).
@@ -58,6 +40,39 @@ max_arity(255).
 :- op(700, xfx, [=, =.., \=]).
 :- op(900, fy, \+).
 
+:- module(builtins, [(=)/2, (\=)/2, (\+)/1, (',')/2, (->)/2, (;)/2,
+                     (=..)/2, (:)/2, (:)/3, (:)/4, (:)/5, (:)/6,
+                     (:)/7, (:)/8, (:)/9, (:)/10, (:)/11, (:)/12,
+                     abolish/1, asserta/1, assertz/1,
+                     at_end_of_stream/0, at_end_of_stream/1,
+                     atom_chars/2, atom_codes/2, atom_concat/3,
+                     atom_length/2, bagof/3, catch/3, char_code/2,
+                     clause/2, close/1, close/2, current_input/1,
+                     current_output/1, current_op/3,
+                     current_predicate/1, current_prolog_flag/2,
+                     expand_goal/2, expand_term/2, fail/0, false/0,
+                     findall/3, findall/4, flush_output/0,
+                     flush_output/1, get_byte/1, get_byte/2,
+                     get_char/1, get_char/2, get_code/1, get_code/2,
+                     halt/0, halt/1, max_arity/1, number_chars/2,
+                     number_codes/2, once/1, op/3, open/3, open/4,
+                     peek_byte/1, peek_byte/2, peek_char/1,
+                     peek_char/2, peek_code/1, peek_code/2,
+                     put_byte/1, put_byte/2, put_code/1, put_code/2,
+                     put_char/1, put_char/2, read_term/2, read_term/3,
+                     repeat/0, retract/1, set_prolog_flag/2,
+                     set_input/1, set_stream_position/2, set_output/1,
+                     setof/3, stream_property/2, sub_atom/5,
+                     subsumes_term/2, term_variables/2, throw/1,
+                     true/0, unify_with_occurs_check/2, write/1,
+                     write_canonical/1, write_term/2, write_term/3,
+                     writeq/1]).
+
+
+% the maximum arity flag. needs to be replaced with
+% current_prolog_flag(max_arity, MAX_ARITY).
+max_arity(1023).
+
 % unify.
 X = X.
 
@@ -72,6 +87,57 @@ Module : Predicate :-
     ; throw(error(type_error(atom, Module), (:)/2))
     ).
 
+:(Module, Predicate, A1) :-
+    ( atom(Module) -> '$module_call'(A1, Module, Predicate)
+    ; throw(error(type_error(atom, Module), (:)/2))
+    ).
+
+:(Module, Predicate, A1, A2) :-
+    ( atom(Module) -> '$module_call'(A1, A2, Module, Predicate)
+    ; throw(error(type_error(atom, Module), (:)/2))
+    ).
+
+:(Module, Predicate, A1, A2, A3) :-
+    ( atom(Module) -> '$module_call'(A1, A2, A3, Module, Predicate)
+    ; throw(error(type_error(atom, Module), (:)/2))
+    ).
+
+:(Module, Predicate, A1, A2, A3, A4) :-
+    ( atom(Module) -> '$module_call'(A1, A2, A3, A4, Module, Predicate)
+    ; throw(error(type_error(atom, Module), (:)/2))
+    ).
+
+:(Module, Predicate, A1, A2, A3, A4, A5) :-
+    ( atom(Module) -> '$module_call'(A1, A2, A3, A4, A5, Module, Predicate)
+    ; throw(error(type_error(atom, Module), (:)/2))
+    ).
+
+:(Module, Predicate, A1, A2, A3, A4, A5, A6) :-
+    ( atom(Module) -> '$module_call'(A1, A2, A3, A4, A5, A6, Module, Predicate)
+    ; throw(error(type_error(atom, Module), (:)/2))
+    ).
+
+:(Module, Predicate, A1, A2, A3, A4, A5, A6, A7) :-
+    ( atom(Module) -> '$module_call'(A1, A2, A3, A4, A5, A6, A7, Module, Predicate)
+    ; throw(error(type_error(atom, Module), (:)/2))
+    ).
+
+:(Module, Predicate, A1, A2, A3, A4, A5, A6, A7, A8) :-
+    ( atom(Module) -> '$module_call'(A1, A2, A3, A4, A5, A6, A7, A8, Module, Predicate)
+    ; throw(error(type_error(atom, Module), (:)/2))
+    ).
+
+:(Module, Predicate, A1, A2, A3, A4, A5, A6, A7, A8, A9) :-
+    ( atom(Module) -> '$module_call'(A1, A2, A3, A4, A5, A6, A7, A8, A9, Module, Predicate)
+    ; throw(error(type_error(atom, Module), (:)/2))
+    ).
+
+:(Module, Predicate, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10) :-
+    ( atom(Module) -> '$module_call'(A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, Module, Predicate)
+    ; throw(error(type_error(atom, Module), (:)/2))
+    ).
+
+
 % flags.
 
 current_prolog_flag(Flag, false) :- Flag == bounded, !.
@@ -125,13 +191,13 @@ set_prolog_flag(Flag, _) :-
 
 fail :- '$fail'.
 
-\+ G :- G, !, false.
+\+ G :- call(G), !, false.
 \+ _.
 
 X \= X :- !, false.
 _ \= _.
 
-once(G) :- G, !.
+once(G) :- call(G), !.
 
 repeat.
 repeat :- repeat.
@@ -148,56 +214,94 @@ comma_errors(G1, G2, B) :- '$call_with_default_policy'(','(G1, G2, B)).
 		 '$set_cp'(B),
 		 '$call_with_default_policy'(comma_errors(G1, G2, B)).
 ','(!, Atom, B) :- Atom == !, '$set_cp'(B).
-','(!, G, B)  :- '$set_cp'(B), G.
+','(!, G, B)  :- '$set_cp'(B), call(G).
 ','(G, CF, B) :- compound(CF),
-		 '$call_with_default_policy'(CF = ','(G1, G2)), !, G,
+		 '$call_with_default_policy'(CF = ','(G1, G2)),
+		 !,
+		 call(G),
 		 '$call_with_default_policy'(comma_errors(G1, G2, B)).
-','(G, Atom, B) :- Atom == !, !, G, '$set_cp'(B).
-','(G1, G2, _)  :- G1, G2.
+','(G, Atom, B) :- Atom == !, !, call(G), '$set_cp'(B).
+','(G1, G2, _)  :- call(G1), call(G2).
 
 ;(G1, G2) :- '$get_b_value'(B), ;(G1, G2, B).
 
+:- non_counted_backtracking semicolon_compound_selector/3.
+semicolon_compound_selector(->(G2, G3), G4, B) :-
+    (  call(G2) ->
+       call(G3)
+    ;  '$set_cp'(B),
+       call(G4)
+    ).
+semicolon_compound_selector(','(G2, G3), G4, B) :-
+    (  ','(G2, G3, B)
+    ;  '$set_cp'(B),
+       call(G4)
+    ).
+semicolon_compound_selector(';'(G2, G3), G4, B) :-
+    (  ';'(G2, G3, B)
+    ;  '$set_cp'(B),
+       call(G4)
+    ).
+
 :- non_counted_backtracking (;)/3.
-;(G1, G4, B) :- compound(G1),
-		'$call_with_default_policy'(G1 = ->(G2, G3)),
-		!,
-		(G2 -> G3 ; '$set_cp'(B), G4).
-;(G1, G2, B) :- G1 == !, '$set_cp'(B), G2.
-;(G1, G2, B) :- G2 == !, G1, '$set_cp'(B).
-;(G, _, _) :- G.
-;(_, G, _) :- G.
+;(G1, G4, B) :-
+    ( (  G1 = (_ -> _)
+      ;  G1 = (_ , _)
+      ;  G1 = (_ ; _)
+      ) ->
+      !,
+      semicolon_compound_selector(G1, G4, B)
+    ).
+;(G1, G2, B) :-
+    G1 == !, !, '$set_cp'(B), call(G2).
+;(G1, G2, B) :-
+    G2 == !, !, call(G1), '$set_cp'(B).
+;(G, _, _) :-
+    call(G).
+;(_, G, _) :-
+    call(G).
 
 G1 -> G2 :- '$get_b_value'(B), '$call_with_default_policy'(->(G1, G2, B)).
 
 :- non_counted_backtracking (->)/3.
-->(G1, G2, B) :- G2 == !, G1, '$set_cp'(B).
-->(G1, G2, B) :- G1, '$set_cp'(B), G2.
+->(G1, G2, B) :- G2 == !, call(G1), '$set_cp'(B).
+->(G1, G2, B) :- call(G1), '$set_cp'(B), call(G2).
 
 % univ.
 
 :- non_counted_backtracking univ_errors/3.
 univ_errors(Term, List, N) :-
     '$skip_max_list'(N, -1, List, R),
-    ( var(R)       -> ( var(Term), throw(error(instantiation_error, (=..)/2))      % 8.5.3.3 a)
-		      ; true )
-    ; R \== []     -> throw(error(type_error(list, List), (=..)/2))                % 8.5.3.3 b)
-    ; List = [H|T] -> ( var(H), var(Term), % R == [] => List is a proper list.
-		        throw(error(instantiation_error, (=..)/2))                 % 8.5.3.3 c)
-		      ; T \== [], nonvar(H), \+ atom(H),
-			throw(error(type_error(atom, H), (=..)/2))                 % 8.5.3.3 d)
-		      ; compound(H), T == [],
-			throw(error(type_error(atomic, H), (=..)/2))               % 8.5.3.3 e)
-		      ; var(Term), max_arity(M), N - 1 > M,
-			throw(error(representation_error(max_arity), (=..)/2))     % 8.5.3.3 g)
-		      ; true )
-    ; var(Term)    -> throw(error(domain_error(non_empty_list, List), (=..)/2))    % 8.5.3.3 f)
-    ; true ).
+    ( var(R)        ->
+       (  var(Term), throw(error(instantiation_error, (=..)/2))      % 8.5.3.3 a)
+       ;  true
+       )
+    ;  R \== []     ->
+       throw(error(type_error(list, List), (=..)/2))                % 8.5.3.3 b)
+    ;  List = [H|T] ->
+       (  var(H), var(Term), % R == [] => List is a proper list.
+       	  throw(error(instantiation_error, (=..)/2))                 % 8.5.3.3 c)
+       ;  T \== [], nonvar(H), \+ atom(H),
+       	  throw(error(type_error(atom, H), (=..)/2))                 % 8.5.3.3 d)
+       ;  compound(H), T == [],
+       	  throw(error(type_error(atomic, H), (=..)/2))               % 8.5.3.3 e)
+       ;  var(Term), max_arity(M), N - 1 > M,
+       	  throw(error(representation_error(max_arity), (=..)/2))     % 8.5.3.3 g)
+       ;  true
+       )
+    ;  var(Term)    ->
+       throw(error(domain_error(non_empty_list, List), (=..)/2))    % 8.5.3.3 f)
+    ;  true
+    ).
 
 Term =.. List :- '$call_with_default_policy'(univ_errors(Term, List, N)),
 		 '$call_with_default_policy'(univ_worker(Term, List, N)).
 
+
 :- non_counted_backtracking univ_worker/3.
-univ_worker(Term, List, _) :- atomic(Term), !, '$call_with_default_policy'(List = [Term]).
+
+univ_worker(Term, List, _) :-
+    atomic(Term), !, '$call_with_default_policy'(List = [Term]).
 univ_worker(Term, [Name|Args], N) :-
     var(Term), !,
     '$call_with_default_policy'(Arity is N-1),
@@ -208,7 +312,9 @@ univ_worker(Term, List, _) :-
     '$call_with_default_policy'(get_args(Args, Term, 1, Arity)),
     '$call_with_default_policy'(List = [Name|Args]).
 
+
 :- non_counted_backtracking get_args/4.
+
 get_args(Args, _, _, 0) :-
     !, '$call_with_default_policy'(Args = []).
 get_args([Arg], Func, N, N) :-
@@ -218,34 +324,39 @@ get_args([Arg|Args], Func, I0, N) :-
     '$call_with_default_policy'(I1 is I0 + 1),
     '$call_with_default_policy'(get_args(Args, Func, I1, N)).
 
-% write, write_canonical, writeq, write_term.
-is_write_option(Functor) :-
-    Functor =.. [Name, Arg],
-    ( Arg == true -> true
-    ; Arg == false -> true
-    ; Name == variable_names -> must_be_var_names_list(Arg)
-    ; var(Arg) -> throw(error(instantiation_error, write_term/2))
-    ; throw(error(domain_error(write_option, Functor), write_term/2))
-    ), % 8.14.2.3 e)
-    ( Name == ignore_ops -> true
-    ; Name == quoted -> true
-    ; Name == numbervars -> true
-    ; Name == variable_names -> true
-    ; throw(error(domain_error(write_option, Functor), write_term/2))
-    ). % 8.14.2.3 e)
+parse_write_options(Options, OptionValues, Stub) :-
+    DefaultOptions = [ignore_ops-false, max_depth-0, numbervars-false,
+                      quoted-false, variable_names-[]],
+    parse_options_list(Options, parse_write_options_, DefaultOptions, OptionValues, Stub).
 
-inst_member_or([X|Xs], Y, Z) :-
-    (  var(X) -> throw(error(instantiation_error, write_term/2))
-    ;  is_write_option(X) -> ( Y = X, ! ; inst_member_or(Xs, Y, Z) )
-    ;  throw(error(domain_error(write_option, X), write_term/2))
+parse_write_options_(ignore_ops(IgnoreOps), ignore_ops-IgnoreOps) :-
+    (  nonvar(IgnoreOps), lists:member(IgnoreOps, [true, false])
+    ;
+       throw(error(domain_error(write_option, ignore_ops(IgnoreOps)), _))
+    ).
+parse_write_options_(quoted(Quoted), quoted-Quoted) :-
+    (  nonvar(Quoted), lists:member(Quoted, [true, false])
+    ;
+       throw(error(domain_error(write_option, quoted(Quoted)), _))
+    ).
+parse_write_options_(numbervars(NumberVars), numbervars-NumberVars) :-
+    (  nonvar(NumberVars), lists:member(NumberVars, [true, false])
+    ;
+       throw(error(domain_error(write_option, numbervars(NumberVars)), _))
+    ).
+parse_write_options_(variable_names(VNNames), variable_names-VNNames) :-
+    must_be_var_names_list(VNNames).
+parse_write_options_(max_depth(MaxDepth), max_depth-MaxDepth) :-
+    (  integer(MaxDepth), MaxDepth >= 0
+    ;
+       throw(error(domain_error(write_option, max_depth(MaxDepth)), _))
     ).
-inst_member_or([], Y, Y).
 
 must_be_var_names_list(VarNames) :-
     '$skip_max_list'(_, -1, VarNames, Tail),
     (  Tail == [] -> must_be_var_names_list_(VarNames, VarNames)
     ;  var(Tail)  -> throw(error(instantiation_error, write_term/2))
-    ;  throw(error(domain_error(write_options, variable_names(VarNames)), write_term/2))
+    ;  throw(error(domain_error(write_option, variable_names(VarNames)), write_term/2))
     ).
 
 must_be_var_names_list_([], List).
@@ -254,44 +365,90 @@ must_be_var_names_list_([VarName | VarNames], List) :-
        (  VarName = (Atom = _) ->
 	      (  atom(Atom) -> must_be_var_names_list_(VarNames, List)
 	      ;  var(Atom)  -> throw(error(instantiation_error, write_term/2))
-	      ;  throw(error(domain_error(write_options, variable_names(List)), write_term/2))
+	      ;  throw(error(domain_error(write_option, variable_names(List)), write_term/2))
 	      )
-       ;  throw(error(domain_error(write_options, variable_names(List)), write_term/2))
+       ;  throw(error(domain_error(write_option, variable_names(List)), write_term/2))
        )
-    ;  throw(error(instantiation_error, write_term/2)) % throw(error(domain_error(write_options, variable_names(List)), write_term/2))
+    ;  throw(error(instantiation_error, write_term/2))
     ).
 
-write_term(_, Options) :-
-    var(Options), throw(error(instantiation_error, write_term/2)).
+
 write_term(Term, Options) :-
-    '$skip_max_list'(_, -1, Options, Options0),
-    (  var(Options0)  -> throw(error(instantiation_error, write_term/2))
-    ;  Options0 == [] -> true
-    ;  throw(error(type_error(list, Options), write_term/2))
-    ), % 8.14.2.3 c)
-    inst_member_or(Options, ignore_ops(IgnoreOps), ignore_ops(false)),
-    inst_member_or(Options, numbervars(NumberVars), numbervars(false)),
-    inst_member_or(Options, quoted(Quoted), quoted(false)),
-    inst_member_or(Options, variable_names(VarNames), variable_names([])),
-    '$write_term'(Term, IgnoreOps, NumberVars, Quoted, VarNames).
+    current_output(Stream),
+    write_term(Stream, Term, Options).
 
-write(Term) :- write_term(Term, [numbervars(true)]).
+write_term(Stream, Term, Options) :-
+    parse_write_options(Options, [IgnoreOps, MaxDepth, NumberVars, Quoted, VNNames], write_term/3),
+    '$write_term'(Stream, Term, IgnoreOps, NumberVars, Quoted, VNNames, MaxDepth).
 
-write_canonical(Term) :- write_term(Term, [ignore_ops(true), quoted(true)]).
 
-writeq(Term) :- write_term(Term, [quoted(true), numbervars(true)]).
+write(Term) :-
+    current_output(Stream),
+    '$write_term'(Stream, Term, false, true, false, [], 0).
 
-%% TODO: complete the predicate! Most read options are missing.
-read_term(Term, Options) :-
-    '$skip_max_list'(_, -1, Options, Options0),
-    (  Options0 == [] -> true
-    ;  var(Options0)  -> throw(error(instantiation_error, read_term/2)) % 8.14.1.3 b)
-    ;  throw(error(type_error(list, Options), read_term/2)) % 8.14.1.3 d)
-    ),
-    (  Options = [variable_names(VarList)] -> '$read_term'(Term, VarList)
-    ;  Options = [] -> read(Term)
-    ;  false
+write_canonical(Term) :-
+    current_output(Stream),
+    '$write_term'(Stream, Term, true, false, true, [], 0).
+
+writeq(Term) :-
+    current_output(Stream),
+    '$write_term'(Stream, Term, false, true, true, [], 0).
+
+
+
+select_rightmost_options([Option-Value | OptionPairs], OptionValues) :-
+    (  pairs:same_key(Option, OptionPairs, OtherValues, _),
+       OtherValues == []  ->
+       OptionValues = [Value | OptionValues0],
+       select_rightmost_options(OptionPairs, OptionValues0)
+    ;
+       select_rightmost_options(OptionPairs, OptionValues)
     ).
+select_rightmost_options([], []).
+
+
+parse_options_list(Options, Selector, DefaultPairs, OptionValues, Stub) :-
+    '$skip_max_list'(_, -1, Options, Tail),
+    (  Tail == [] ->
+       true
+    ;  var(Tail) ->
+       throw(error(instantiation_error, Stub))       % 8.11.5.3c)
+    ;  Tail \== [] ->
+       throw(error(type_error(list, Options), Stub)) % 8.11.5.3e)
+    ),
+    (  lists:maplist(nonvar, Options),
+       catch(lists:maplist(Selector, Options, OptionPairs0),
+             error(E, _),
+             throw(error(E, Stub))) ->
+       lists:append(DefaultPairs, OptionPairs0, OptionPairs1),
+       keysort(OptionPairs1, OptionPairs),
+       select_rightmost_options(OptionPairs, OptionValues)
+    ;
+       throw(error(instantiation_error, Stub))       % 8.11.5.3c)
+    ).
+
+
+parse_read_term_options(Options, OptionValues, Stub) :-
+    DefaultOptions = [singletons-_, variables-_, variable_names-_],
+    parse_options_list(Options, parse_read_term_options_, DefaultOptions, OptionValues, Stub).
+
+
+parse_read_term_options_(singletons(Vars), singletons-Vars).
+parse_read_term_options_(variables(Vars), variables-Vars).
+parse_read_term_options_(variable_names(Vars), variable_names-Vars).
+parse_read_term_options_(E,_) :-
+    throw(error(domain_error(read_option, E), _)).
+
+
+
+read_term(Stream, Term, Options) :-
+    parse_read_term_options(Options, [Singletons, VariableNames, Variables], read_term/3),
+    '$read_term'(Stream, Term, Singletons, Variables, VariableNames).
+
+read_term(Term, Options) :-
+    current_input(Stream),
+    read_term(Stream, Term, Options).
+
 
 % expand_goal.
 
@@ -318,7 +475,8 @@ catch(G,C,R) :- '$get_current_block'(Bb), '$call_with_default_policy'(catch(G,C,
 
 :- non_counted_backtracking catch/4.
 catch(G,C,R,Bb) :-
-    '$install_new_block'(NBb), call(G),
+    '$install_new_block'(NBb),
+    call(G),
     '$call_with_default_policy'(end_block(Bb, NBb)).
 catch(G,C,R,Bb) :-
     '$reset_block'(Bb),
@@ -382,7 +540,7 @@ set_difference([], _, []) :- !.
 set_difference(Xs, [], Xs).
 
 group_by_variant([V2-S2 | Pairs], V1-S1, [S2 | Solutions], Pairs0) :-
-    non_iso:variant(V1, V2), !, V1 = V2, group_by_variant(Pairs, V2-S2, Solutions, Pairs0).
+    iso_ext:variant(V1, V2), !, V1 = V2, group_by_variant(Pairs, V2-S2, Solutions, Pairs0).
 group_by_variant(Pairs, _, [], Pairs).
 
 group_by_variants([V-S|Pairs], [V-Solution|Solutions]) :-
@@ -390,7 +548,10 @@ group_by_variants([V-S|Pairs], [V-Solution|Solutions]) :-
     group_by_variants(Pairs0, Solutions).
 group_by_variants([], []).
 
-iterate_variants([V-Solution|GroupSolutions], V, Solution).
+iterate_variants([V-Solution|GroupSolutions], V, Solution) :-
+    (  GroupSolutions == [] -> !
+    ;  true
+    ).
 iterate_variants([_|GroupSolutions], Ws, Solution) :-
     iterate_variants(GroupSolutions, Ws, Solution).
 
@@ -406,7 +567,9 @@ findall_with_existential(Template, Goal, PairedSolutions, Witnesses0, Witnesses)
     (  nonvar(Goal), Goal = _ ^ _ ->
        rightmost_power(Goal, Goal1, ExistentialVars0),
        term_variables(ExistentialVars0, ExistentialVars),
-       set_difference(Witnesses0, ExistentialVars, Witnesses),
+       sort(Witnesses0, Witnesses1),
+       sort(ExistentialVars, ExistentialVars1),
+       set_difference(Witnesses1, ExistentialVars1, Witnesses),
        findall(Witnesses-Template, Goal1, PairedSolutions)
     ;  Witnesses = Witnesses0,
        findall(Witnesses-Template, Goal, PairedSolutions)
@@ -425,7 +588,10 @@ bagof(Template, Goal, Solution) :-
     iterate_variants(GroupedSolutions, Witnesses, Solution).
 
 iterate_variants_and_sort([V-Solution0|GroupSolutions], V, Solution) :-
-    sort(Solution0, Solution).
+    sort(Solution0, Solution),
+    (  GroupSolutions == [] -> !
+    ;  true
+    ).
 iterate_variants_and_sort([_|GroupSolutions], Ws, Solution) :-
     iterate_variants_and_sort(GroupSolutions, Ws, Solution).
 
@@ -465,18 +631,19 @@ setof(Template, Goal, Solution) :-
 
 clause(H, B) :-
     (  var(H) -> throw(error(instantiation_error, clause/2))
-    ;  functor(H, Name, Arity) -> (  Name == '.' -> throw(error(type_error(callable, H), clause/2))
-				  ;  Name == (:), Arity =:= 2 ->
-				     arg(1, H, Module),
-				     arg(2, H, F),
-				     '$module_clause'(F, B, Module)
-				  %% '$no_such_predicate' fails if H is not callable.
-				  ;  '$no_such_predicate'(H) -> '$fail'
-				  ;  '$head_is_dynamic'(H) -> '$clause_body_is_valid'(B),
-							      '$get_clause'(H, B)
-				  ;  throw(error(permission_error(access, private_procedure, Name/Arity),
-						 clause/2))
-				  )
+    ;  functor(H, Name, Arity) ->
+       (  Name == '.' -> throw(error(type_error(callable, H), clause/2))
+	   ;  Name == (:), Arity =:= 2 ->
+		  arg(1, H, Module),
+		  arg(2, H, F),
+		  '$module_clause'(F, B, Module)
+	   %% '$no_such_predicate' fails if H is not callable.
+	   ;  '$no_such_predicate'(H) -> '$fail'
+	   ;  '$head_is_dynamic'(H) -> '$clause_body_is_valid'(B),
+							       '$get_clause'(H, B)
+	   ;  throw(error(permission_error(access, private_procedure, Name/Arity),
+					  clause/2))
+	   )
     ;  throw(error(type_error(callable, H), clause/2))
     ).
 
@@ -548,9 +715,11 @@ assertz_clause(Head, Body) :-
 	 arg(1, Head, Module),
 	 arg(2, Head, F),
 	 module_assertz_clause(F, Body, Module)
-       ; '$no_such_predicate'(Head) -> call_assertz(Head, Body, Name, Arity)
-       ; '$head_is_dynamic'(Head) -> call_assertz(Head, Body, Name, Arity)
-       ;  throw(error(permission_error(modify, static_procedure, Name/Arity), assertz/1))
+       ; '$no_such_predicate'(Head) ->
+	 call_assertz(Head, Body, Name, Arity)
+       ; '$head_is_dynamic'(Head) ->
+	 call_assertz(Head, Body, Name, Arity)
+       ; throw(error(permission_error(modify, static_procedure, Name/Arity), assertz/1))
        )
     ;  throw(error(type_error(callable, Head), assertz/1))
     ).
@@ -561,12 +730,13 @@ assertz(Clause) :-
     ).
 
 first_match_index([Clause0 | Clauses], Clause1, N0, N) :-
-    (  Clause0 \= Clause1 -> N1 is N0 + 1,
-			     first_match_index(Clauses, Clause1, N1, N)
+    (  Clause0 \= Clause1 ->
+       N1 is N0 + 1,
+       first_match_index(Clauses, Clause1, N1, N)
     ;  N0 = N, Clause0 = Clause1
     ).
 
-retract_clauses([Clause|Clauses0], Head, Body, Name, Arity) :-
+retract_clauses([Clause | Clauses0], Head, Body, Name, Arity) :-
     functor(VarHead, Name, Arity),
     findall((VarHead :- VarBody), clause(VarHead, VarBody), Clauses1),
     first_match_index(Clauses1, (Head :- Body), 0, N),
@@ -574,7 +744,7 @@ retract_clauses([Clause|Clauses0], Head, Body, Name, Arity) :-
     ;  true
     ),
     '$retract_clause'(Name, Arity, N, Clauses1).
-retract_clauses([_|Clauses0], Head, Body, Name, Arity) :-
+retract_clauses([_ | Clauses0], Head, Body, Name, Arity) :-
     retract_clauses(Clauses0, Head, Body, Name, Arity).
 
 call_retract(Head, Body, Name, Arity) :-
@@ -744,7 +914,14 @@ op(Priority, OpSpec, Op) :-
     ;  throw(error(type_error(list, Op), op/3)) % 8.14.3.3 f)
     ).
 
-halt :- '$halt'.
+
+halt :- halt(0).
+
+halt(N) :-
+        (   -2^31 =< N, N =< 2^31 - 1 ->
+            '$halt'(N)
+        ;   throw(error(domain_error(exit_code, N), halt/1))
+        ).
 
 atom_length(Atom, Length) :-
     (  var(Atom)  -> throw(error(instantiation_error, atom_length/2)) % 8.16.1.3 a)
@@ -764,10 +941,10 @@ atom_chars(Atom, List) :-
     ),
     (  var(Atom) ->
        (  var(Tail) -> throw(error(instantiation_error, atom_chars/2))
-       ;  ground(List), Tail == [] -> '$atom_chars'(Atom, List)
+       ;  ground(List) -> '$atom_chars'(Atom, List)
        ;  throw(error(instantiation_error, atom_chars/2))
        )
-    ;  atom(Atom) -> can_be_chars_or_vars(List, atom_chars/2), '$atom_chars'(Atom, List)
+    ;  atom(Atom) -> '$atom_chars'(Atom, List)
     ;  throw(error(type_error(atom, Atom), atom_chars/2))
     ).
 
@@ -781,7 +958,7 @@ atom_codes(Atom, List) :-
        ;  ground(List), Tail == [] -> '$atom_codes'(Atom, List)
        ;  throw(error(instantiation_error, atom_codes/2))
        )
-    ;  atom(Atom) -> can_be_codes_or_vars(List, atom_codes/2), '$atom_codes'(Atom, List)
+    ;  atom(Atom) -> '$atom_codes'(Atom, List)
     ;  throw(error(type_error(atom, Atom), atom_codes/2))
     ).
 
@@ -838,11 +1015,11 @@ char_code(Char, Code) :-
     ).
 
 get_char(C) :-
-    (  var(C) -> '$get_char'(C)
-    ;  C == end_of_file  -> '$get_char'(C)
-    ;  atom_length(C, 1) -> '$get_char'(C)
-    ;  throw(error(type_error(in_character, C), get_char/1))
-    ).
+    current_input(S),
+    '$get_char'(S, C).
+
+get_char(S, C) :-
+    '$get_char'(S, C).
 
 can_be_number(N, PI) :-
     (  var(N) -> true
@@ -859,37 +1036,6 @@ must_be_number(N, PI) :-
     ;  throw(error(instantiation_error, PI))
     ).
 
-can_be_chars_or_vars(Cs, _) :- var(Cs), !.
-can_be_chars_or_vars(Cs, PI) :- chars_or_vars(Cs, PI).
-
-chars_or_vars([], _).
-chars_or_vars([C|Cs], PI) :-
-    (  nonvar(C) ->
-       (  catch(atom_length(C, 1), _, false) ->
-	  (  nonvar(Cs) -> chars_or_vars(Cs, PI)
-	  ;  false
-	  )
-       ;  throw(error(type_error(character, C), PI))
-       )
-    ;  chars_or_vars(Cs, PI)
-    ).
-
-can_be_codes_or_vars(Cs, _) :- var(Cs), !.
-can_be_codes_or_vars(Cs, PI) :- codes_or_vars(Cs, PI).
-
-codes_or_vars([], _).
-codes_or_vars([C|Cs], PI) :-
-    (  nonvar(C) ->
-       (  catch(char_code(_, C), _, false) ->
-	  (  nonvar(Cs) -> codes_or_vars(Cs, PI)
-	  ;  false
-	  )
-       ;  integer(C) -> throw(error(representation_error(character_code), PI))
-       ;  throw(error(type_error(integer, C), PI))
-       )
-    ;  codes_or_vars(Cs, PI)
-    ).
-
 number_chars(N, Chs) :-
    (  ground(Chs)
    -> can_be_number(N, number_chars/2),
@@ -929,3 +1075,226 @@ subsumes_term(General, Specific) :-
    ).
 
 unify_with_occurs_check(X, Y) :- '$unify_with_occurs_check'(X, Y).
+
+current_input(S) :- '$current_input'(S).
+
+current_output(S) :- '$current_output'(S).
+
+set_input(S) :-
+    (  var(S) ->
+       throw(error(instantiation_error, set_input/1))
+    ;  '$set_input'(S)
+    ).
+
+set_output(S) :-
+    (  var(S) ->
+       throw(error(instantiation_error, set_output/1))
+    ;  '$set_output'(S)
+    ).
+
+
+parse_stream_options(Options, OptionValues, Stub) :-
+    DefaultOptions = [alias-[], eof_action-eof_code, reposition-false, type-text],
+    parse_options_list(Options, parse_stream_options_, DefaultOptions, OptionValues, Stub).
+
+
+parse_stream_options_(type(Type), type-Type) :-
+    (  nonvar(Type), lists:member(Type, [text, binary]), !, true
+    ;
+       throw(error(domain_error(stream_option, type(Type)), _))
+    ).
+parse_stream_options_(reposition(Bool), reposition-Bool) :-
+    (  nonvar(Bool), lists:member(Bool, [true, false]), !, true
+    ;
+       throw(error(domain_error(stream_option, reposition(Bool)), _))
+    ).
+parse_stream_options_(alias(A), alias-A) :-
+    (  atom(A), A \== [], !, true
+    ;
+       throw(error(domain_error(stream_option, alias(A)), _))
+    ).
+parse_stream_options_(eof_action(Action), eof_action-Action) :-
+    (  nonvar(Action), lists:member(Action, [eof_code, error, reset]), !, true
+    ;
+       throw(error(domain_error(stream_option, eof_action(Action)), _))
+    ).
+parse_stream_options_(E, _) :-
+    throw(error(domain_error(stream_option, E), _)). % 8.11.5.3i)
+
+
+open(SourceSink, Mode, Stream) :-
+    open(SourceSink, Mode, Stream, []).
+
+open(SourceSink, Mode, Stream, StreamOptions) :-
+    (  var(SourceSink) ->
+       throw(error(instantiation_error, open/4)) % 8.11.5.3a)
+    ;  var(Mode) ->
+       throw(error(instantiation_error, open/4)) % 8.11.5.3b)
+    ;  \+ atom(Mode) ->
+       throw(error(type_error(atom, Mode), open/4)) % 8.11.5.3d)
+    ;  nonvar(Stream) ->
+       throw(error(type_error(variable, Stream), open/4)) % 8.11.5.3f)
+    ;
+       parse_stream_options(StreamOptions, [Alias, EOFAction, Reposition, Type], open/4),
+       '$open'(SourceSink, Mode, Stream, Alias, EOFAction, Reposition, Type)
+    ).
+
+
+parse_close_options(Options, OptionValues, Stub) :-
+    DefaultOptions = [force-false],
+    parse_options_list(Options, parse_close_options_, DefaultOptions, OptionValues, Stub).
+
+parse_close_options_(force(Force), force-Force) :-
+    (  nonvar(Force), lists:member(Force, [true, false]), !
+    ;
+       throw(error(domain_error(close_option, force(Force)), _))
+    ).
+parse_close_options_(E, _) :-
+    throw(error(domain_error(close_option, E), _)).
+
+
+close(Stream, CloseOptions) :-
+    parse_close_options(CloseOptions, [Force], close/2),
+    '$close'(Stream, CloseOptions).
+
+close(Stream) :-
+    '$close'(Stream, []).
+
+
+flush_output(S) :-
+    '$flush_output'(S).
+
+flush_output :-
+    current_output(S),
+    '$flush_output'(S).
+
+
+get_byte(S, B) :-
+    '$get_byte'(S, B).
+
+get_byte(B) :-
+    current_input(S),
+    '$get_byte'(S, B).
+
+
+put_char(C) :-
+    current_output(S),
+    '$put_char'(S, C).
+
+put_char(S, C) :-
+    '$put_char'(S, C).
+
+
+put_byte(C) :-
+    current_output(S),
+    '$put_byte'(S, C).
+
+put_byte(S, C) :-
+    '$put_byte'(S, C).
+
+
+put_code(C) :-
+    current_output(S),
+    '$put_code'(S, C).
+
+put_code(S, C) :-
+    '$put_code'(S, C).
+
+
+get_code(C) :-
+    current_input(S),
+    '$get_code'(S, C).
+
+get_code(S, C) :-
+    '$get_code'(S, C).
+
+
+peek_byte(S, B) :-
+    '$peek_byte'(S, B).
+
+peek_byte(B) :-
+    current_input(S),
+    '$peek_byte'(S, B).
+
+
+peek_code(C) :-
+    current_input(S),
+    '$peek_code'(S, C).
+
+peek_code(S, C) :-
+    '$peek_code'(S, C).
+
+
+peek_char(C) :-
+    current_input(S),
+    '$peek_char'(S, C).
+
+peek_char(S, C) :-
+    '$peek_char'(S, C).
+
+
+check_stream_property(file_name(F), file_name, F) :-
+    ( var(F) -> true ; atom(F) ).
+check_stream_property(mode(M), mode, M) :-
+    ( var(M) -> true ; lists:member(M, [read, write, append]) ).
+check_stream_property(D, direction, D) :-
+    ( var(D) -> true ; lists:member(D, [input, output, input_output]), ! ).
+check_stream_property(alias(A), alias, A) :-
+    ( var(A) -> true ; atom(A) ).
+check_stream_property(position(P), position, P) :-
+    ( var(P) -> true ; integer(P), P >= 0 ).
+check_stream_property(end_of_stream(E), end_of_stream, E) :-
+    ( var(E) -> true ; lists:member(E, [not, at, past]) ).
+check_stream_property(eof_action(A), eof_action, A) :-
+    ( var(A) -> true ; lists:member(A, [error, eof_code, reset]) ).
+check_stream_property(reposition(B), reposition, B) :-
+    ( var(B) -> true ; lists:member(B, [true, false]) ).
+check_stream_property(type(T), type, T) :-
+    ( var(T) -> true ; lists:member(T, [text, binary]) ).
+
+
+stream_iter_(S, S).
+stream_iter_(S, S1) :-
+    '$next_stream'(S, S0),
+    stream_iter_(S0, S1).
+
+stream_iter(S) :-
+    (  nonvar(S) ->
+       true
+    ;  '$first_stream'(S0),
+       stream_iter_(S0, S)
+    ).
+
+
+stream_property(S, P) :-
+    (  nonvar(P), \+ check_stream_property(P, _, _) ->
+       throw(error(domain_error(stream_property, P), stream_property/2))
+    ;  stream_iter(S),
+       check_stream_property(P, PropertyName, PropertyValue),
+       '$stream_property'(S, PropertyName, PropertyValue)
+    ).
+
+
+at_end_of_stream(S_or_a) :-
+    (  atom(S_or_a) ->
+       stream_property(S, alias(S_or_a))
+    ;  S = S_or_a
+    ),
+    stream_property(S, end_of_stream(E)),
+    ( E = at -> true ; E = past ).
+
+at_end_of_stream :-
+    current_input(S),
+    stream_property(S, end_of_stream(E)),
+    !,
+    ( E = at ; E = past ).
+
+
+set_stream_position(S_or_a, Position) :-
+    (  var(Position) ->
+       throw(error(instantiation_error, set_stream_position/2))
+    ;  integer(Position), Position >= 0 ->
+       true
+    ;  throw(error(domain_error(stream_position, Position)))
+    ),
+    '$set_stream_position'(S_or_a, Position).

src/lib/charsio.pl

@@ -0,0 +1,242 @@
+:- module(charsio, [char_type/2,
+                    chars_utf8bytes/2,
+                    get_single_char/1,
+                    read_line_to_chars/3,
+                    read_term_from_chars/2,
+                    write_term_to_chars/3,
+                    chars_base64/3]).
+
+:- use_module(library(dcgs)).
+:- use_module(library(iso_ext)).
+:- use_module(library(error)).
+:- use_module(library(lists)).
+
+fabricate_var_name(VarType, VarName, N) :-
+    char_code('A', AC),
+    LN is N mod 26 + AC,
+    char_code(LC, LN),
+    NN is N // 26,
+    (  NN =:= 0 ->
+       (  VarType == fabricated ->
+          atom_chars(VarName, ['_', LC])
+       ;  VarType == numbervars ->
+          atom_chars(VarName, [LC])
+       )
+    ;  number_chars(NN, NNChars),
+       (  VarType == fabricated ->
+          atom_chars(VarName, ['_', LC | NNChars])
+       ;  VarType == numbervars ->
+          atom_chars(VarName, [LC | NNChars])
+       )
+    ).
+
+var_list_contains_name([VarName = _ | VarList], VarName0) :-
+    (  VarName == VarName0 -> true
+    ;  var_list_contains_name(VarList, VarName0)
+    ).
+
+var_list_contains_variable([_ = Var | VarList], Var0) :-
+    (  Var == Var0 -> true
+    ;  var_list_contains_variable(VarList, Var0)
+    ).
+
+make_new_var_name(VarType, V, VarName, N, N1, VarList) :-
+    fabricate_var_name(VarType, VarName0, N),
+    (  var_list_contains_name(VarList, VarName0) ->
+       N0 is N + 1,
+       make_new_var_name(VarType, V, VarName, N0, N1, VarList)
+    ;  VarName = VarName0,
+       N1 is N + 1
+    ).
+
+extend_var_list(Vars, VarList, NewVarList, VarType) :-
+    extend_var_list_(Vars, 0, VarList, NewVarList0, VarType),
+    append(VarList, NewVarList0, NewVarList).
+
+extend_var_list_([], _, VarList, [], _).
+extend_var_list_([V|Vs], N, VarList, NewVarList, VarType) :-
+    (  var_list_contains_variable(VarList, V) ->
+       extend_var_list_(Vs, N, VarList, NewVarList, VarType)
+    ;  make_new_var_name(VarType, V, VarName, N, N1, VarList),
+       NewVarList = [VarName = V | NewVarList0],
+       extend_var_list_(Vs, N1, VarList, NewVarList0, VarType)
+    ).
+
+
+char_type(Char, Type) :-
+    (   var(Char) -> instantiation_error(char_type/2)
+    ;   atom_length(Char, 1) ->
+        (   ground(Type) ->
+            (   ctype(Type) ->
+                '$char_type'(Char, Type)
+            ;   domain_error(char_type, Type, char_type/2)
+            )
+        ;   ctype(Type),
+            '$char_type'(Char, Type)
+        )
+    ;   type_error(in_character, Char, char_type/2)
+    ).
+
+
+ctype(alnum).
+ctype(alpha).
+ctype(alphabetic).
+ctype(ascii).
+ctype(ascii_graphic).
+ctype(ascii_punctuation).
+ctype(binary_digit).
+ctype(control).
+ctype(decimal_digit).
+ctype(exponent).
+ctype(graphic).
+ctype(hexadecimal_digit).
+ctype(layout).
+ctype(lower).
+ctype(meta).
+ctype(numeric).
+ctype(octal_digit).
+ctype(prolog).
+ctype(sign).
+ctype(solo).
+ctype(symbolic_control).
+ctype(symbolic_hexadecimal).
+ctype(upper).
+ctype(whitespace).
+
+
+get_single_char(C) :-
+    (  var(C) -> '$get_single_char'(C)
+    ;  atom_length(C, 1) -> '$get_single_char'(C)
+    ;  type_error(in_character, C, get_single_char/1)
+    ).
+
+
+read_term_from_chars(Chars, Term) :-
+    (  var(Chars) ->
+       instantiation_error(read_term_from_chars/2)
+    ;  nonvar(Term) ->
+       throw(error(uninstantiation_error(Term), read_term_from_chars/2))
+    ;  '$skip_max_list'(_, -1, Chars, Chars0),
+       Chars0 == [],
+       partial_string(Chars) ->
+       true
+    ;
+       type_error(complete_string, Chars, read_term_from_chars/2)
+    ),
+    '$read_term_from_chars'(Chars, Term).
+
+
+write_term_to_chars(_, Options, _) :-
+    var(Options), instantiation_error(write_term_to_chars/3).
+write_term_to_chars(Term, Options, Chars) :-
+    builtins:parse_write_options(Options,
+                                 [IgnoreOps, MaxDepth, NumberVars, Quoted, VNNames],
+                                 write_term_to_chars/3),
+    (  nonvar(Chars)  ->
+       throw(error(uninstantiation_error(Chars), write_term_to_chars/3))
+    ;
+       true
+    ),
+    term_variables(Term, Vars),
+    extend_var_list(Vars, VNNames, NewVarNames, numbervars),
+    '$write_term_to_chars'(Chars, Term, IgnoreOps, NumberVars, Quoted, NewVarNames, MaxDepth).
+
+% Encodes Ch character to list of Bytes.
+char_utf8bytes(Ch, Bytes) :-
+  char_code(Ch, Code),
+  phrase(code_to_utf8(Code), Bytes).
+
+code_to_utf8(Code) --> {Code @< 0x80},     [Code], !.
+code_to_utf8(Code) --> {Code @< 0x800},    encode(Code, 0xC0, 2), !.
+code_to_utf8(Code) --> {Code @< 0x10000},  encode(Code, 0xE0, 3), !.
+code_to_utf8(Code) --> {Code @< 0x110000}, encode(Code, 0xF0, 4), !.
+
+encode(_, _, 0) --> !.
+encode(Code, Prefix, Nb) -->
+  { Nb1 is Nb - 1, Byte is Prefix \/ ((Code >> (6 * Nb1)) /\ 0x3F) },
+  [Byte], encode(Code, 0x80, Nb1).
+
+% Maps characters and UTF-8 bytes.
+% If Cs is a variable, parses Bs as a list of UTF-8 bytes.
+% Otherwise, transform the list of characters Cs to UTF-8 bytes.
+chars_utf8bytes(Cs, Bs) :-
+  var(Cs), must_be(list, Bs) ->
+    once(phrase(decode_utf8(Cs), Bs))
+  ; (must_be(list, Cs),
+     maplist(must_be(atom), Cs),
+     maplist(char_utf8bytes, Cs, Bss),
+     append(Bss, Bs)).
+
+decode_utf8([]) --> [].
+decode_utf8(Chars) --> leading(Nb, Code), continuation(Code, Chars, Nb).
+
+leading(1, Byte) --> [Byte], {Byte /\ 0x80 =:= 0}.
+leading(2, Code) --> [Byte], {Byte /\ 0xE0 =:= 0xC0, Code is Byte - 0xC0}.
+leading(3, Code) --> [Byte], {Byte /\ 0xF0 =:= 0xE0, Code is Byte - 0xE0}.
+leading(4, Code) --> [Byte], {Byte /\ 0xF8 =:= 0xF0, Code is Byte - 0xF0}.
+leading(1, 0xFFFD) --> [_]. % invalid first byte
+
+continuation(Code, [H|T], 1) --> {char_code(H, Code)}, decode_utf8(T).
+continuation(Code, Chars, Nb) --> [Byte],
+  {Nb1 is Nb - 1, Byte /\ 0xC0 =:= 0x80, NextCode is (Code << 6) \/ (Byte - 0x80)},
+  continuation(NextCode, Chars, Nb1).
+
+% invalid continuation byte
+% each remaining continuation byte (if any) will raise 0xFFFD too
+continuation(_, ['\xFFFD\'|T], _) --> [_], decode_utf8(T).
+
+
+read_line_to_chars(Stream, Cs0, Cs) :-
+        '$get_n_chars'(Stream, 1, Char), % this also works for binary streams
+        (   Char == [] -> Cs0 = Cs
+        ;   Char = [C],
+            Cs0 = [C|Rest],
+            (   C == '\n' -> Rest = Cs
+            ;   read_line_to_chars(Stream, Rest, Cs)
+            )
+        ).
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   Relation between a list of characters Cs and its Base64 encoding Bs,
+   also a list of characters.
+
+   At least one of the arguments must be instantiated.
+
+   Options are:
+
+      - padding(Boolean)
+        Whether to use padding: true (the default) or false.
+      - charset(C)
+        Either 'standard' (RFC 4648 §4, the default) or 'url' (RFC 4648 §5).
+
+   Example:
+
+      ?- chars_base64("hello", Bs, []).
+         Bs = "aGVsbG8="
+      ;  false.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+chars_base64(Cs, Bs, Options) :-
+        must_be(list, Options),
+        (   member(O, Options), var(O) ->
+            instantiation_error(chars_base64/3)
+        ;   (   member(padding(Padding), Options) -> true
+            ;   Padding = true
+            ),
+            (   member(charset(Charset), Options) -> true
+            ;   Charset = standard
+            )
+        ),
+        must_be(boolean, Padding),
+        must_be(atom, Charset),
+        (   member(Charset, [standard,url]) -> true
+        ;   domain_error(charset, Charset, chars_base64/3)
+        ),
+        (   var(Cs) ->
+            must_be(list, Bs),
+            maplist(must_be(character), Bs),
+            '$chars_base64'(Cs, Bs, Padding, Charset)
+        ;   must_be(list, Cs),
+            maplist(must_be(character), Cs),
+            '$chars_base64'(Cs, Bs, Padding, Charset)
+        ).

src/lib/clpb.pl

@@ -16,11 +16,9 @@
    Public operators.
 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 
-:- op(300, fy, ~).
-:- op(500, yfx, #).
-
-:- module(clpb, [
-                 sat/1,
+:- module(clpb, [op(300, fy, ~),
+		 op(500, yfx, #),
+		 sat/1,
                  taut/2,
                  labeling/1,
                  sat_count/2,
@@ -32,9 +30,11 @@
 :- use_module(library(between)).
 :- use_module(library(atts)).
 :- use_module(library(lists)).
-:- use_module(library(non_iso)).
+:- use_module(library(iso_ext)).
+:- use_module(library(random)).
+:- use_module(library(pairs)).
 :- use_module(library(dcgs)).
-%:- use_module(library(types)).
+:- use_module(library(error), [domain_error/3, type_error/3]).
 
 :- attribute
         clpb/1,
@@ -77,8 +77,8 @@ must_be(list(What), Where, Term) :- !,
 must_be(ground, _, Term) :- !,
         functor(Term, _, _).
 
-must_be(Type, Goal-Arg, Term) :-
-        must_be(Term, Type, Goal, Arg).
+must_be(Type, _, Term) :-
+        error:must_be(Type, Term).
 
 clpz_list(Nil, _) :- Nil == [].
 clpz_list(Ls, Where) :-
@@ -87,7 +87,6 @@ clpz_list(Ls, Where) :-
     ;   Ls = [_|Rest],
         clpz_list(Rest, Where)
     ).
-    
 
 
 instantiation_error(Term) :- instantiation_error(Term, unknown(Term)-1).
@@ -99,72 +98,14 @@ instantiation_error(_, Goal-Arg) :-
 domain_error(Expectation, Term) :-
         domain_error(Expectation, Term, unknown(Term)-1).
 
-domain_error(Expectation, Term, Goal-Arg) :-
-        throw(error(domain_error(Expectation, Term), domain_error(Goal, Arg, Expectation, Term))).
-
 
 type_error(Expectation, Term) :-
         type_error(Expectation, Term, unknown(Term)-1).
 
-type_error(Expectation, Term, Goal-Arg) :-
-        throw(error(type_error(Expectation, Term), type_error(Goal, Arg, Expectation, Term))).
-
-
-/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-   foldl/4
-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
-
-foldl(Goal_3, Ls, A0, A) :-
-        foldl_(Ls, Goal_3, A0, A).
-
-foldl_([], _, A, A).
-foldl_([L|Ls], G_3, A0, A) :-
-        call(G_3, L, A0, A1),
-        foldl_(Ls, G_3, A1, A).
-
-/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-   foldl/5
-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
-
-foldl(Goal_4, Xs, Ys, A0, A) :-
-        foldl_(Xs, Ys, Goal_4, A0, A).
-
-foldl_([], [], _, A, A).
-foldl_([X|Xs], [Y|Ys], G_4, A0, A) :-
-        call(G_4, X, Y, A0, A1),
-        foldl_(Xs, Ys, G_4, A1, A).
-
-
 partition(Pred, Ls0, As, Bs) :-
         include(Pred, Ls0, As),
         exclude(Pred, Ls0, Bs).
 
-sum_list(Ls, S) :- sumlist(Ls, S).
-
-/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-  Pairs.
-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
-
-pairs_keys_values([], [], []).
-pairs_keys_values([A-B|ABs], [A|As], [B|Bs]) :-
-        pairs_keys_values(ABs, As, Bs).
-
-pairs_keys(Ps, Ks) :- pairs_keys_values(Ps, Ks, _).
-
-pairs_values(Ps, Vs) :- pairs_keys_values(Ps, _, Vs).
-
-map_list_to_pairs(Pred, Ls, Ps) :-
-        map_list_to_pairs2(Ls, Pred, Ps).
-
-map_list_to_pairs2([], _, []).
-map_list_to_pairs2([H|T0], Pred, [K-H|T]) :-
-        call(Pred, H, K),
-        map_list_to_pairs2(T0, Pred, T).
-
-
-
-
-
 goal_expansion(get_attr(Var, Module, Value), (var(Var),get_atts(Var, Access))) :-
         Access =.. [Module,Value].
 
@@ -728,10 +669,6 @@ existential(V, BDD, Node) :-
    Counter network for card(Is,Fs).
 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 
-same_length([], []).
-same_length([_|As], [_|Bs]) :-
-        same_length(As, Bs).
-
 counter_network(Cs, Fs, Node) :-
         same_length([_|Fs], Indicators),
         fill_indicators(Indicators, 0, Cs),
@@ -1242,8 +1179,7 @@ bdd_count(Node, VNum, Count) :-
                 bdd_count(High, VNum, HCount),
                 bdd_pow(Low, V, VNum, LPow),
                 bdd_pow(High, V, VNum, HPow),
-                Count0 is LPow*LCount + HPow*HCount,
-                Count = Count0
+                Count is LPow*LCount + HPow*HCount
             )
         ).
 

src/lib/cont.pl

@@ -0,0 +1,30 @@
+:- module(cont, [reset/3, shift/1]).
+
+reset(Goal, Ball, Cont) :-
+    call(Goal),
+    '$reset_cont_marker',
+    '$bind_from_register'(Cont, 3),
+    '$bind_from_register'(Ball, 4).
+
+shift(Ball) :-
+    '$nextEP'(first, E, P),
+    get_chunks(E, P, L),
+    (  L == [] ->
+       Cont = cont(true)
+    ;  Cont = cont(call_continuation(L))
+    ),
+    '$write_cont_and_term'(_, _, Cont, Ball),
+    '$unwind_environments'.
+
+get_chunks(E, P, L) :-
+    (  '$points_to_cont_reset_marker'(P) ->
+       L = []
+    ;  '$get_cont_chunk'(E,P,TB),
+       L = [TB|Rest],
+       '$nextEP'(E, NextE, NextP),
+       get_chunks(NextE, NextP, Rest)
+    ).
+
+call_continuation(L) :- '$call_continuation'(L).
+
+'$write_cont_and_term'(_, _, _, _).

src/lib/crypto.pl

@@ -0,0 +1,826 @@
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   Written May 2020 by Markus Triska (triska@metalevel.at)
+   Part of Scryer Prolog.
+
+   Predicates for cryptographic applications.
+
+   This library assumes that the Prolog flag double_quotes is set to chars.
+   In Scryer Prolog, lists of characters are very efficiently represented,
+   and strings have the advantage that the atom table remains unmodified.
+
+   Especially for cryptographic applications, it as an advantage that
+   using strings leaves little trace of what was processed in the system.
+
+   For predicates that accept an encoding/1 option to specify the encoding
+   of the input data, if encoding(octet) is used, then the input can also
+   be specified as a list of bytes, i.e., integers between 0 and 255.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+:- module(crypto,
+          [hex_bytes/2,                  % ?Hex, ?Bytes
+           crypto_n_random_bytes/2,      % +N, -Bytes
+           crypto_data_hash/3,           % +Data, -Hash, +Options
+           crypto_data_hkdf/4,           % +Data, +Length, -Bytes, +Options
+           crypto_password_hash/2,       % +Password, ?Hash
+           crypto_password_hash/3,       % +Password, -Hash, +Options
+           crypto_data_encrypt/6,        % +PlainText, +Algorithm, +Key, +IV, -CipherText, +Options
+           crypto_data_decrypt/6,        % +CipherText, +Algorithm, +Key, +IV, -PlainText, +Options
+           ed25519_new_keypair/1,        % -KeyPair
+           ed25519_keypair_public_key/2, % +KeyPair, +PublicKey
+           ed25519_sign/4,               % +KeyPair, +Data, -Signature, +Options
+           ed25519_verify/4,             % +PublicKey, +Data, +Signature, +Options
+           curve25519_generator/1,       % -Generator
+           curve25519_scalar_mult/3,     % +Scalar, +Point, -Result
+           crypto_name_curve/2,          % +Name, -Curve
+           crypto_curve_order/2,         % +Curve, -Order
+           crypto_curve_generator/2,     % +Curve, -Generator
+           crypto_curve_scalar_mult/4    % +Curve, +Scalar, +Point, -Result
+          ]).
+
+:- use_module(library(error)).
+:- use_module(library(lists)).
+:- use_module(library(between)).
+:- use_module(library(dcgs)).
+:- use_module(library(clpz)).
+:- use_module(library(arithmetic)).
+:- use_module(library(format)).
+:- use_module(library(charsio)).
+:- use_module(library(si)).
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   hex_bytes(?Hex, ?Bytes) is det.
+
+   Relation between a hexadecimal sequence and a list of bytes. Hex
+   is a string of hexadecimal numbers. Bytes is a list of *integers*
+   between 0 and 255 that represent the sequence as a list of bytes.
+   At least one of the arguments must be instantiated.
+
+   Example:
+
+   ?- hex_bytes("501ACE", Bs).
+      Bs = [80,26,206]
+   ;  false.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+
+hex_bytes(Hs, Bytes) :-
+        (   ground(Hs) ->
+            must_be(list, Hs),
+            maplist(must_be(atom), Hs),
+            (   phrase(hex_bytes(Hs), Bytes) ->
+                true
+            ;   domain_error(hex_encoding, Hs, hex_bytes/2)
+            )
+        ;   must_be_bytes(Bytes, hex_bytes/2),
+            phrase(bytes_hex(Bytes), Hs)
+        ).
+
+hex_bytes([]) --> [].
+hex_bytes([H1,H2|Hs]) --> [Byte],
+        { char_hexval(H1, High),
+          char_hexval(H2, Low),
+          Byte #= High*16 + Low },
+        hex_bytes(Hs).
+
+bytes_hex([]) --> [].
+bytes_hex([B|Bs]) --> [C0,C1],
+        { High #= B>>4,
+          Low #= B /\ 0xf,
+          char_hexval(C0, High),
+          char_hexval(C1, Low)
+        },
+        bytes_hex(Bs).
+
+char_hexval(C, H) :- nth0(H, "0123456789abcdef", C), !.
+char_hexval(C, H) :- nth0(H, "0123456789ABCDEF", C), !.
+
+
+must_be_bytes(Bytes, Context) :-
+        must_be(list, Bytes),
+        maplist(must_be(integer), Bytes),
+        (   member(B, Bytes), \+ between(0, 255, B) ->
+            type_error(byte, B, Context)
+        ;   true
+        ).
+
+
+must_be_byte_chars(Chars, Context) :-
+        must_be(list, Chars),
+        (   member(Char, Chars),
+            char_code(Char, Code),
+            \+ between(0, 255, Code) ->
+            domain_error(byte_char, Char, Context)
+        ;   true
+        ).
+
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   Cryptographically secure random numbers
+   =======================================
+
+   crypto_n_random_bytes(+N, -Bytes) is det
+
+   Bytes is unified with a list of N cryptographically secure
+   pseudo-random bytes. Each byte is an integer between 0 and 255. If
+   the internal pseudo-random number generator (PRNG) has not been
+   seeded with enough entropy to ensure an unpredictable byte
+   sequence, an exception is thrown.
+
+   One way to relate such a list of bytes to an _integer_ is to use
+   CLP(ℤ) constraints as follows:
+
+   :- use_module(library(clpz)).
+   :- use_module(library(lists)).
+
+   bytes_integer(Bs, N) :-
+           foldl(pow, Bs, 0-0, N-_).
+
+   pow(B, N0-I0, N-I) :-
+           B in 0..255,
+           N #= N0 + B*256^I0,
+           I #= I0 + 1.
+
+   With this definition, we can generate a random 256-bit integer
+   _from_ a list of 32 random _bytes_:
+
+   ?- crypto_n_random_bytes(32, Bs),
+      bytes_integer(Bs, I).
+      Bs = [146,166,162,210,242,7,25,132,64,94|...],
+      I = 337420085690608915485...(56 digits omitted)
+
+   The above relation also works in the other direction, letting you
+   translate an integer _to_ a list of bytes. In addition, you can
+   use hex_bytes/2 to convert bytes to _tokens_ that can be easily
+   exchanged in your applications.
+
+   ?- crypto_n_random_bytes(12, Bs),
+      hex_bytes(Hex, Bs).
+      Bs = [34,25,50,72,58,63,50,172,32,46|...], Hex = "221932483a3f32ac202 ..."
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+
+crypto_n_random_bytes(N, Bs) :-
+        must_be(integer, N),
+        length(Bs, N),
+        maplist(crypto_random_byte, Bs).
+
+crypto_random_byte(B) :- '$crypto_random_byte'(B).
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   Hashing
+   =======
+
+   crypto_data_hash(+Data, -Hash, +Options)
+
+   Where Data is a list of characters, and Hash is the computed hash
+   as a list of hexadecimal characters.
+
+   Options is a list of:
+
+     - algorithm(+A)
+       where A is one of ripemd160, sha256, sha384, sha512, sha512_256,
+       sha3_224, sha3_256, sha3_384, sha3_512, blake2s256, blake2b512,
+       or a variable. If A is a variable, then it is unified with the
+       default algorithm, which is an algorithm that is considered
+       cryptographically secure at the time of this writing.
+     - encoding(+Encoding)
+       The default encoding is utf8. The alternative is octet,
+       to treat the input as a list of raw bytes.
+
+   Example:
+
+   ?- crypto_data_hash("abc", Hs, [algorithm(sha256)]).
+      Hs = "ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad"
+   ;  false.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   SHA256 is the current default for several hash-related predicates.
+   It is deemed sufficiently secure for the foreseeable future.  Yet,
+   application programmers must be aware that the default may change in
+   future versions. The hash predicates all yield the algorithm they
+   used if a Prolog variable is used for the pertaining option.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+crypto_data_hash(Data0, Hash, Options0) :-
+        must_be(list, Options0),
+        options_data_chars(Options0, Data0, Data, Encoding),
+        functor_hash_options(algorithm, A, Options0, _),
+        (   hash_algorithm(A) -> true
+        ;   domain_error(hash_algorithm, A, crypto_data_hash/3)
+        ),
+        '$crypto_data_hash'(Data, Encoding, HashBytes, A),
+        hex_bytes(Hash, HashBytes).
+
+options_data_chars(Options, Data, Chars, Encoding) :-
+        option(encoding(Encoding), Options, utf8),
+        must_be(atom, Encoding),
+        encoding_chars(Encoding, Data, Chars).
+
+default_hash(sha256).
+
+functor_hash_options(F, Hash, Options0, [Option|Options]) :-
+        Option =.. [F,Hash],
+        (   select(Option, Options0, Options) ->
+            (   var(Hash) ->
+                default_hash(Hash)
+            ;   must_be(atom, Hash)
+            )
+        ;   Options = Options0,
+            default_hash(Hash)
+        ).
+
+hash_algorithm(ripemd160).
+hash_algorithm(sha256).
+hash_algorithm(sha512).
+hash_algorithm(sha384).
+hash_algorithm(sha512_256).
+hash_algorithm(sha3_224).
+hash_algorithm(sha3_256).
+hash_algorithm(sha3_384).
+hash_algorithm(sha3_512).
+hash_algorithm(blake2s256).
+hash_algorithm(blake2b512).
+
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   crypto_data_hkdf(+Data, +Length, -Bytes, +Options) is det.
+
+   Concentrate possibly dispersed entropy of Data and then expand it
+   to the desired length. Data is a list of characters.
+
+   Bytes is unified with a list of bytes of length Length, and is
+   suitable as input keying material and initialization vectors to
+   symmetric encryption algorithms.
+
+   Admissible options are:
+
+     - algorithm(+Algorithm)
+       One of sha256, sha384 or sha512. If you specify a variable,
+       then it is unified with the algorithm that was used, which is a
+       cryptographically secure algorithm by default.
+     - info(+Info)
+       Optional context and application specific information,
+       specified as a list of characters. The default is [].
+     - salt(+List)
+       Optionally, a list of bytes that are used as salt. The
+       default is all zeroes.
+     - encoding(+Encoding)
+       The default encoding is utf8. The alternative is octet,
+       to treat the input as a list of raw bytes.
+
+   The `info/1`  option can be  used to  generate multiple keys  from a
+   single  master key,  using for  example values  such as  "key" and
+   "iv", or the name of a file that is to be encrypted.
+
+   See crypto_n_random_bytes/2 to obtain a suitable salt.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+crypto_data_hkdf(Data0, L, Bytes, Options0) :-
+        functor_hash_options(algorithm, Algorithm, Options0, Options),
+        (   hkdf_algorithm(Algorithm) -> true
+        ;   domain_error(hkdf_algorithm, Algorithm, crypto_data_hkdf/4)
+        ),
+        must_be(integer, L),
+        L >= 0,
+        options_data_chars(Options, Data0, Data, Encoding),
+        option(salt(SaltBytes), Options, []),
+        must_be_bytes(SaltBytes, crypto_data_hkdf/4),
+        option(info(Info0), Options, []),
+        chars_bytes_(Info0, Info, crypto_data_hkdf/4),
+        '$crypto_data_hkdf'(Data, Encoding, SaltBytes, Info, Algorithm, L, Bytes).
+
+hkdf_algorithm(sha256).
+hkdf_algorithm(sha384).
+hkdf_algorithm(sha512).
+
+option(What, Options, Default) :-
+        (   member(V, Options), var(V) ->
+            instantiation_error(option/3)
+        ;   true
+        ),
+        (   member(What, Options) -> true
+        ;   What =.. [_,Default]
+        ).
+
+chars_bytes_(Cs, Bytes, Context) :-
+        must_be(list, Cs),
+        (   maplist(integer, Cs) -> Bytes = Cs
+        ;   chars_utf8bytes(Cs, Bytes)
+        ),
+        must_be_bytes(Bytes, Context).
+
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   The so-called modular crypt format (MCF) is a standard for encoding
+   password hash strings. However, there's no official specification
+   document describing it. Nor is there a central registry of
+   identifiers or rules. This page describes what is known about it:
+
+   https://pythonhosted.org/passlib/modular_crypt_format.html
+
+   As of 2016, the MCF is deprecated in favor of the PHC String Format:
+
+   https://github.com/P-H-C/phc-string-format/blob/master/phc-sf-spec.md
+
+   This is what we are using below. For the time being, it is best to
+   treat these hashes as opaque terms in applications. Please let me
+   know if you need to rely on any specifics of this format.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   crypto_password_hash(+Password, ?Hash) is semidet.
+
+   If Hash is instantiated, the predicate succeeds _iff_ the hash
+   matches the given password. Otherwise, the call is equivalent to
+   crypto_password_hash(Password, Hash, []) and computes a
+   password-based hash using the default options.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+crypto_password_hash(Password0, Hash) :-
+        (   nonvar(Hash) ->
+            chars_bytes_(Password0, Password, crypto_password_hash/2),
+            must_be(list, Hash),
+            dollar_segments(Hash, [[],"pbkdf2-sha512",[t,=|CsIterations],SaltB64,HashB64]),
+            number_chars(Iterations, CsIterations),
+            bytes_base64(SaltBytes, SaltB64),
+            bytes_base64(HashBytes, HashB64),
+            '$crypto_password_hash'(Password, SaltBytes, Iterations, HashBytes)
+        ;   crypto_password_hash(Password0, Hash, [])
+        ).
+
+
+dollar_segments(Ls, Segments) :-
+        (   append(Front, [$|Ds], Ls) ->
+            Segments = [Front|Rest],
+            dollar_segments(Ds, Rest)
+        ;   Segments = [Ls]
+        ).
+
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   crypto_password_hash(+Password, -Hash, +Options) is det.
+
+   Derive Hash based on Password. This predicate is similar to
+   crypto_data_hash/3 in that it derives a hash from given data.
+   However, it is tailored for the specific use case of _passwords_.
+   One essential distinction is that for this use case, the derivation
+   of a hash should be _as slow as possible_ to counteract brute-force
+   attacks over possible passwords.
+
+   Another important distinction is that equal passwords must yield,
+   with very high probability, _different_ hashes. For this reason,
+   cryptographically strong random numbers are automatically added to
+   the password before a hash is derived.
+
+   Hash is unified with a string that contains the computed hash and
+   all parameters that were used, except for the password. Instead of
+   storing passwords, store these hashes. Later, you can verify the
+   validity of a password with crypto_password_hash/2, comparing the
+   then entered password to the stored hash. If you need to export this
+   atom, you should treat it as opaque ASCII data with up to 255 bytes
+   of length. The maximal length may increase in the future.
+
+   Admissible options are:
+
+     - algorithm(+Algorithm)
+       The algorithm to use. Currently, the only available algorithm
+       is 'pbkdf2-sha512', which is therefore also the default.
+     - cost(+C)
+       C is an integer, denoting the binary logarithm of the number
+       of _iterations_ used for the derivation of the hash. This
+       means that the number of iterations is set to 2^C. Currently,
+       the default is 17, and thus more than one hundred _thousand_
+       iterations. You should set this option as high as your server
+       and users can tolerate. The default is subject to change and
+       will likely increase in the future or adapt to new algorithms.
+     - salt(+Salt)
+       Use the given list of bytes as salt. By default,
+       cryptographically secure random numbers are generated for this
+       purpose. The default is intended to be secure, and constitutes
+       the typical use case of this predicate.
+
+   Currently, PBKDF2 with SHA-512 is used as the hash derivation
+   function, using 128 bits of salt. All default parameters, including
+   the algorithm, are subject to change, and other algorithms will also
+   become available in the future. Since computed hashes store all
+   parameters that were used during their derivation, such changes will
+   not affect the operation of existing deployments. Note though that
+   new hashes will then be computed with the new default parameters.
+
+   See crypto_data_hkdf/4 for generating keys from Hash.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+crypto_password_hash(Password0, Hash, Options) :-
+        chars_bytes_(Password0, Password, crypto_password_hash/3),
+        must_be(list, Options),
+        option(cost(C), Options, 17),
+        Iterations is 2^C,
+        Algorithm = 'pbkdf2-sha512', % current default and only option
+        option(algorithm(Algorithm), Options, Algorithm),
+        (   member(salt(SaltBytes), Options) ->
+            must_be_bytes(SaltBytes, crypto_password_hash/2)
+        ;   crypto_n_random_bytes(16, SaltBytes)
+        ),
+        '$crypto_password_hash'(Password, SaltBytes, Iterations, HashBytes),
+        bytes_base64(HashBytes, HashB64),
+        bytes_base64(SaltBytes, SaltB64),
+        phrase(format_("$pbkdf2-sha512$t=~d$~s$~s", [Iterations,SaltB64,HashB64]), Hash).
+
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   Bidirectional Bytes <-> Base64 conversion *without padding*.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+bytes_base64(Bytes, Base64) :-
+        (   var(Bytes) ->
+            chars_base64(Chars, Base64, [padding(false)]),
+            maplist(char_code, Chars, Bytes)
+        ;   maplist(char_code, Chars, Bytes),
+            chars_base64(Chars, Base64, [padding(false)])
+        ).
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   crypto_data_encrypt(+PlainText,
+                       +Algorithm,
+                       +Key,
+                       +IV,
+                       -CipherText,
+                       +Options).
+
+   Encrypt the given PlainText, using the symmetric algorithm
+   Algorithm, key Key, and initialization vector (or nonce) IV, to
+   give CipherText.
+
+   PlainText must be a list of characters, Key and IV must be lists of
+   bytes, and CipherText is created as a list of characters.
+
+   Keys and IVs can be chosen at random (using for example
+   crypto_n_random_bytes/2) or derived from input keying material (IKM)
+   using for example crypto_data_hkdf/4. This input is often a shared
+   secret, such as a negotiated point on an elliptic curve, or the hash
+   that was computed from a password via crypto_password_hash/3 with a
+   freshly generated and specified _salt_.
+
+   Reusing the same combination of Key and IV typically leaks at least
+   _some_ information about the plaintext. For example, identical
+   plaintexts will then correspond to identical ciphertexts. For some
+   algorithms, reusing an IV with the same Key has disastrous results
+   and can cause the loss of all properties that are otherwise
+   guaranteed. Especially in such cases, an IV is also called a
+   _nonce_ (number used once).
+
+   It is safe to store and  transfer the used initialization vector (or
+   nonce) in plain text, but the key _must be kept secret_.
+
+   Currently, the only supported algorithm is 'chacha20-poly1305', a
+   powerful and efficient _authenticated_ encryption scheme, providing
+   secrecy and at the same time reliable protection against undetected
+   _modifications_ of the encrypted data. This is a very good choice
+   for virtually all use cases. It is a stream cipher and can encrypt
+   data of any length up to 256 GB. Further, the encrypted data has
+   exactly the same length as the original, and no padding is used.
+
+   Options:
+
+      - encoding(+Encoding)
+      Encoding to use for PlainText. Default is utf8. The alternative
+      is octet to treat PlainText as raw bytes.
+
+      - tag(-List)
+      For authenticated encryption schemes, List is unified with a
+      list of _bytes_ holding the tag. This tag must be provided for
+      decryption.
+
+   Here is an example encryption and decryption, using the ChaCha20
+   stream cipher with the Poly1305 authenticator. This cipher uses a
+   256-bit key and a 96-bit nonce, i.e., 32 and 12 _bytes_,
+   respectively:
+
+    ?- Algorithm = 'chacha20-poly1305',
+       crypto_n_random_bytes(32, Key),
+       crypto_n_random_bytes(12, IV),
+       crypto_data_encrypt("this text is to be encrypted", Algorithm,
+                   Key, IV, CipherText, [tag(Tag)]),
+       crypto_data_decrypt(CipherText, Algorithm,
+                   Key, IV, RecoveredText, [tag(Tag)]).
+
+   Yielding:
+
+       Algorithm = 'chacha20-poly1305',
+       Key = [113,247,153,134,177,220,13,193,50,150|...],
+       IV = [135,20,149,153,63,35,68,114,247,171|...],
+       CipherText = "\x94\0Ej\x94\®Â\x95\óÑÆXÃn¾ð©b\x1c\ ...",
+       RecoveredText = "this text is to be  ...",
+       Tag = [152,117,152,17,162,75,150,206,144,40|...]
+
+   In this example, we use crypto_n_random_bytes/2 to generate a key
+   and nonce from cryptographically secure random numbers. For
+   repeated applications, you must ensure that a nonce is only used
+   _once_ together with the same key. Note that for _authenticated_
+   encryption schemes, the _tag_ that was computed during encryption
+   is necessary for decryption. It is safe to store and transfer the
+   tag in plain text.
+
+   See also crypto_data_decrypt/6, and hex_bytes/2 for conversion
+   between bytes and hex encoding.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+crypto_data_encrypt(PlainText0, Algorithm, Key, IV, CipherText, Options) :-
+        options_data_chars(Options, PlainText0, PlainText, Encoding),
+        option(tag(Tag), Options, _),
+        (   nonvar(Tag) ->
+            must_be_bytes(Tag, crypto_data_encrypt/6)
+        ;   true
+        ),
+        must_be_bytes(Key, crypto_data_encrypt/6),
+        must_be_bytes(IV, crypto_data_encrypt/6),
+        must_be(atom, Algorithm),
+        (   Algorithm = 'chacha20-poly1305' -> true
+        ;   domain_error('chacha20-poly1305', Algorithm, crypto_data_encrypt/6)
+        ),
+        '$crypto_data_encrypt'(PlainText, Encoding, Key, IV, Tag, CipherText).
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+  crypto_data_decrypt(+CipherText,
+                      +Algorithm,
+                      +Key,
+                      +IV,
+                      -PlainText,
+                      +Options).
+
+   Decrypt the given CipherText, using the symmetric algorithm
+   Algorithm, key Key, and initialization vector IV, to give
+   PlainText. CipherText must be a list of characters, and Key and IV
+   must be lists of bytes. PlainText is created as a list of
+   characters.
+
+   Currently, the only supported algorithm is 'chacha20-poly1305',
+   a very secure, fast and versatile authenticated encryption method.
+
+   Options is a list of:
+
+    - encoding(+Encoding)
+    Encoding to use for PlainText. The default is utf8. The
+    alternative is octet, which is used if the data are raw bytes.
+
+    - tag(+Tag)
+    For authenticated encryption schemes, the tag must be specified as
+    a list of bytes exactly as they were generated upon encryption.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+crypto_data_decrypt(CipherText0, Algorithm, Key, IV, PlainText, Options) :-
+        option(tag(Tag), Options, []),
+        must_be_bytes(Tag, crypto_data_decrypt/6),
+        must_be_bytes(Key, crypto_data_decrypt/6),
+        must_be_bytes(IV, crypto_data_decrypt/6),
+        must_be(atom, Algorithm),
+        option(encoding(Encoding), Options, utf8),
+        must_be(atom, Encoding),
+        member(Encoding, [utf8,octet]),
+        must_be(list, CipherText0),
+        encoding_chars(octet, CipherText0, CipherText1),
+        maplist(char_code, TagChars, Tag),
+        append(CipherText1, TagChars, CipherText),
+        (   Algorithm = 'chacha20-poly1305' -> true
+        ;   domain_error('chacha20-poly1305', Algorithm, crypto_data_decrypt/6)
+        ),
+        '$crypto_data_decrypt'(CipherText, octet, Key, IV, Encoding, PlainText).
+
+
+encoding_chars(octet, Bs, Cs) :-
+        must_be(list, Bs),
+        (   maplist(integer, Bs) ->
+            maplist(char_code, Cs, Bs)
+        ;   Bs = Cs
+        ),
+        must_be_byte_chars(Cs, crypto_encoding).
+encoding_chars(utf8, Cs, Cs) :-
+        must_be(list, Cs),
+        maplist(must_be(character), Cs).
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   Digital signatures with Ed25519
+   ===============================
+
+   - ed25519_new_keypair(-Pair)
+     Yields a new Ed25519 key pair Pair, a list of characters. The
+     pair contains the private key and must be kept absolutely secret.
+     Pair can be used for signing. Its public key can be obtained
+     with ed25519_keypair_public_key/2.
+
+   - ed25519_keypair_public_key(+Pair, -PublicKey)
+     PublicKey is the public key of the given key pair. The public key
+     can be used for signature verification, and can be shared freely.
+     The public key is represented as a list of characters.
+
+   - ed25519_sign(+Key, +Data, -Signature, +Options)
+     Key and Data must be lists of characters. Key is a key pair in
+     PKCS#8 v2 format as generated by ed25519_new_keypair/1. Sign Data
+     with Key, yielding Signature as a list of hexadecimal characters.
+
+   - ed25519_verify(+Key, +Data, +Signature, +Options)
+     Key and Data must be lists of characters. Key is a public key.
+     Succeeds if Data was signed with the private key corresponding to
+     Key, where Signature is a list of hexadecimal characters as
+     generated by ed25519_sign/4. Fails otherwise.
+
+   Currently, the only option for signing and verifying is:
+
+     - encoding(+Encoding)
+       The default encoding of Data is utf8. The alternative is octet,
+       which treats Data as a list of raw bytes.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+ed25519_new_keypair(Pair) :-
+        '$ed25519_new_keypair'(Pair).
+
+ed25519_keypair_public_key(Pair, PublicKey) :-
+        must_be_byte_chars(Pair, ed25519_keypair_public_key),
+        '$ed25519_keypair_public_key'(Pair, octet, PublicKey).
+
+ed25519_sign(Key, Data0, Signature, Options) :-
+        must_be_byte_chars(Key, ed25519_sign),
+        options_data_chars(Options, Data0, Data, Encoding),
+        '$ed25519_sign'(Key, octet, Data, Encoding, Signature0),
+        hex_bytes(Signature, Signature0).
+
+ed25519_verify(Key, Data0, Signature0, Options) :-
+        must_be_byte_chars(Key, ed25519_verify),
+        options_data_chars(Options, Data0, Data, Encoding),
+        hex_bytes(Signature0, Signature),
+        '$ed25519_verify'(Key, octet, Data, Encoding, Signature).
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   X25519: ECDH key exchange over Curve25519
+   =========================================
+
+   Points on Curve25519 are represented as lists of characters that denote
+   the u-coordinate of the Montgomery curve.
+
+   - curve25519_generator(-Gs)
+     Gs is the generator point of Curve25519.
+
+   - curve25519_scalar_mult(+Scalar, +Ps, -Rs)
+     Scalar must be an integer between 0 and 2^256-1,
+     or a list of 32 bytes, and Ps must be a point on the curve.
+     Computes the point Rs = Scalar*Ps as mandated by X25519.
+
+   Alice and Bob can use this to establish a shared secret as follows,
+   where Gs is the generator point of Curve25519:
+
+     1. Alice creates a random integer a and sends As = a*Gs to Bob.
+     2. Bob creates a random integer b and sends Bs = b*Gs to Alice.
+     3. Alice computes Rs = a*Bs.
+     4. Bob computes Rs = b*As.
+     5. Alice and Bob use crypto_data_hkdf/4 on Rs with suitable
+        (same) parameters to obtain lists of bytes that can be used as
+        keys and initialization vectors for symmetric encryption.
+
+   If a and b are kept secret, this method is considered very secure.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+curve25519_generator(Gs) :-
+        length(Gs0, 32),
+        Gs0 = [9|Zs],
+        maplist(=(0), Zs),
+        maplist(char_code, Gs, Gs0).
+
+curve25519_scalar_mult(Scalar, Point, Result) :-
+        (   integer_si(Scalar) ->
+            Scalar #>= 0,
+            Scalar #< 2^256,
+            length(ScalarBytes, 32),
+            bytes_integer(ScalarBytes, Scalar)
+        ;   ScalarBytes = Scalar,
+            must_be_bytes(ScalarBytes, curve25519_scalar_mult/3),
+            length(ScalarBytes, 32)
+        ),
+        maplist(char_code, Point, PointBytes),
+        '$curve25519_scalar_mult'(ScalarBytes, PointBytes, Result).
+
+bytes_integer(Bs, N) :-
+        foldl(pow, Bs, 0-0, N-_).
+
+pow(B, N0-I0, N-I) :-
+        B in 0..255,
+        N #= N0 + B*256^I0,
+        I #= I0 + 1.
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   Operations on Elliptic Curves
+   =============================
+
+   Sample use: Establishing a shared secret S, using ECDH key exchange.
+
+    ?- crypto_name_curve(secp256k1, C),
+       crypto_curve_generator(C, Generator),
+       PrivateKey = 10,
+       crypto_curve_scalar_mult(C, PrivateKey, Generator, PublicKey),
+       Random = 12,
+       crypto_curve_scalar_mult(C, Random, Generator, R),
+       crypto_curve_scalar_mult(C, Random, PublicKey, S),
+       crypto_curve_scalar_mult(C, PrivateKey, R, S).
+
+   For better security, new code should use Curve25519 instead.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   An elliptic curve over a prime field F_p is represented as:
+
+   curve(Name,P,A,B,point(X,Y),Order,FieldLength,Cofactor).
+
+   First, we define suitable accessors.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+curve_name(curve(Name,_,_,_,_,_,_,_), Name).
+curve_p(curve(_,P,_,_,_,_,_,_), P).
+curve_a(curve(_,_,A,_,_,_,_,_), A).
+curve_b(curve(_,_,_,B,_,_,_,_), B).
+curve_field_length(curve(_,_,_,_,_,_,FieldLength,_), FieldLength).
+
+crypto_curve_generator(curve(_,_,_,_,G,_,_,_), G).
+crypto_curve_order(curve(_,_,_,_,_,Order,_,_), Order).
+
+crypto_curve_scalar_mult(Curve, Scalar, point(X,Y), point(RX, RY)) :-
+        must_be(integer, Scalar),
+        must_be_on_curve(Curve, point(X,Y)),
+        curve_name(Curve, Name),
+        curve_field_length(Curve, L0),
+        L #= 2*L0, % for hex encoding
+        phrase(format_("04~|~`0t~16r~*+~`0t~16r~*+", [X,L,Y,L]), Hex),
+        hex_bytes(Hex, Bytes),
+        '$crypto_curve_scalar_mult'(Name, Scalar, Bytes, SX, SY),
+        number_chars(RX, SX),
+        number_chars(RY, SY).
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+?- crypto_name_curve(secp256k1, Curve),
+   crypto_curve_generator(Curve, G),
+   crypto_curve_scalar_mult(Curve, 2, G, R).
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   Validation.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+curve_contains_point(Curve, point(QX,QY)) :-
+        curve_a(Curve, A),
+        curve_b(Curve, B),
+        curve_p(Curve, P),
+        QY^2 mod P #= (QX^3 + A*QX + B) mod P.
+
+must_be_on_curve(Curve, P) :-
+        \+ curve_contains_point(Curve, P),
+        domain_error(point_on_curve, P, crypto_elliptic_curves).
+must_be_on_curve(Curve, P) :- curve_contains_point(Curve, P).
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   Predefined curves
+   =================
+
+   List available curves:
+
+   $ openssl ecparam -list_curves
+
+   Show curve parameters for secp256k1:
+
+   $ openssl ecparam -param_enc explicit -conv_form uncompressed \
+                     -text -no_seed -name secp256k1
+
+   You must remove the leading "04:" from the generator.
+
+   The field length depends on the order of the curve and can be computed
+   with order_field_length/2.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+order_field_length(Order, L) :-
+        fitting_exponent(Order, 0, E),
+        L #= (E + 7) // 8.
+
+fitting_exponent(N, E0, E) :-
+        (   2^E0 #>= N -> E #= E0
+        ;   E1 #= E0 + 1,
+            fitting_exponent(N, E1, E)
+        ).
+
+crypto_name_curve(secp112r1,
+                  curve(secp112r1,
+                        0x00db7c2abf62e35e668076bead208b,
+                        0x00db7c2abf62e35e668076bead2088,
+                        0x659ef8ba043916eede8911702b22,
+                        point(0x09487239995a5ee76b55f9c2f098,
+                              0xa89ce5af8724c0a23e0e0ff77500),
+                        0x00db7c2abf62e35e7628dfac6561c5,
+                        14,
+                        1)).
+crypto_name_curve(secp256k1,
+                  curve(secp256k1,
+                        0x00fffffffffffffffffffffffffffffffffffffffffffffffffffffffefffffc2f,
+                        0x0,
+                        0x7,
+                        point(0x79be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798,
+                              0x483ada7726a3c4655da4fbfc0e1108a8fd17b448a68554199c47d08ffb10d4b8),
+                        0x00fffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141,
+                        32,
+                        1)).

src/lib/csv.pl

@@ -0,0 +1,238 @@
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+  Predicates for parsing CSV data
+
+
+  Read csv files
+
+  Only two options with default values :
+  - token_separator(',')
+  - with_header(true)
+
+  Examples
+
+  * parsing a csv string:
+
+  ?- use_module(library(csv)).
+  ?- use_module(library(dcgs)).
+  ?- phrase(parse_csv(Data), "col1,col2,col3,col4\none,2,,three").
+    Data = frame(["col1","col2","col3","col4"],[["one",2,[],"three"]]).
+
+  * with some options:
+
+  ?- phrase(parse_csv(Data, [with_header(false), token_separator(';')]), "one;2;;three").
+    Data = frame([],[["one",2,[],"three"]]).
+
+  * parsing a csv file:
+
+  ?- use_module(library(csv)).
+  ?- use_module(library(pio)).
+  ?- phrase_from_file(parse_csv(frame(Header, Rows)), './test.csv').
+
+
+  Write csv files
+
+  Four options with default values :
+  - line_separator('\n')
+  - token_separator(',')
+  - with_header(true)
+  - null_value(empty)
+
+  Examples
+
+  * writing a csv file:
+
+  ?- use_module(library(csv)).
+  ?- write_csv('./test.csv', frame(["col1","col2","col3","col4"], [["one",2,[],"three"]])).
+
+  * with some options
+
+  ?- use_module(library(csv)).
+  ?- write_csv('./test.csv', frame(["col1","col2","col3","col4"], [["one",2,[],"three"]]), [with_header(false), line_separator('\r\n'), token_separator(';'), null_value('\\N')]).
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+:- module(csv, [
+  parse_csv//1,
+  parse_csv//2,
+  write_csv/2,
+  write_csv/3
+]).
+
+:- use_module(library(format)).
+:- use_module(library(dcgs)).
+:- use_module(library(iso_ext)).
+:- use_module(library(lists)).
+
+
+option(W, O) :-
+  ( member(W, O) -> true
+  ; throw(error(domain_error(csv_option, W), option/2))).
+
+
+option_extends([], Opt, Opt).
+option_extends([X | Y], Opt0, Opt) :-
+  functor(X, Name, 1),
+  F0 =.. [Name, _],
+  ( select(F0, Opt0, R) ->
+    option_extends(Y, [X | R], Opt)
+  ; option_extends(Y, [X | Opt0], Opt) ).
+
+
+%% -- write --
+
+
+escaped_field([], []).
+escaped_field(['"' | Y], ['"', '"' | R]) :-
+  escaped_field(Y, R).
+escaped_field([X | Y], [X | R]) :-
+  X \== '"',
+  escaped_field(Y, R).
+
+
+ensure_escaped(Field, Field) :-
+  (atom(Field); integer(Field); float(Field)).
+ensure_escaped([X | Y], Field) :-
+  escaped_field([X | Y], Field).
+
+
+write_field(Out, Field, Opt) :-
+  ( Field \== [] ->
+    ensure_escaped(Field, Field0),
+    format(Out, "~w", [Field0])
+  ; option(null_value(Null_Value), Opt),
+    ( Null_Value == empty -> true
+    ; format(Out, "~w", [Null_Value]))).
+
+
+write_row(Out, [Field], Opt) :-
+  write_field(Out, Field, Opt).
+write_row(Out, [Field, X | Y], Opt) :-
+  write_field(Out, Field, Opt),
+  option(token_separator(Tk_Sep), Opt),
+  format(Out, "~w", [Tk_Sep]),
+  write_row(Out, [X | Y], Opt).
+
+
+write_rows(Out, [Row], Opt) :-
+  write_row(Out, Row, Opt).
+write_rows(Out, [Row, X | Y], Opt) :-
+  option(line_separator(Line_Sep), Opt),
+  write_row(Out, Row, Opt),
+  format(Out, "~w", [Line_Sep]),
+  write_rows(Out, [X | Y], Opt).
+
+
+write_csv_(Out, frame(Header, Rows), Opt) :-
+  option(with_header(With_Header), Opt),
+  ( With_Header == true -> 
+    write_row(Out, Header, Opt),
+    option(line_separator(Line_Sep), Opt),
+    format(Out, "~w", [Line_Sep])
+  ; true),
+  write_rows(Out, Rows, Opt).
+
+
+write_csv(File_Name, Frm, Opt) :-
+  option_extends(Opt, [
+    null_value(empty),
+    token_separator(','),
+    with_header(true),
+    line_separator('\n')
+  ], Opt0),
+  setup_call_cleanup(
+    open(File_Name, write, Out),
+    write_csv_(Out, Frm, Opt0),
+    close(Out)).
+write_csv(File_Name, Frm) :-
+  write_csv(File_Name, Frm, []).
+
+
+%% -- read --
+
+
+tokens([], Opt), [Tk_Sep] -->
+  { option(token_separator(Tk_Sep), Opt) },
+  [Tk_Sep],
+  !.
+tokens([], _), "\r\n" -->
+  "\r\n",
+  !.
+tokens([], _), "\n" -->
+  "\n",
+  !.
+tokens([], _), "\r" -->
+  "\r",
+  !.
+tokens([X | Y], Opt) -->
+  [X],
+  !,
+  tokens(Y, Opt).
+tokens([], _) --> [].
+
+
+field(R, Opt) -->
+  "\"",
+  !,
+  string_tokens(R, Opt).
+field(R, Opt) -->
+  tokens(R0, Opt),
+  { R0 \== [],
+    catch(number_chars(R, R0), _, R = R0)
+  }.
+field([], _) --> [].
+
+
+string_tokens(R, Opt) -->
+  [X],
+  ( { X == '"' } ->
+    ( "\"" ->
+      { R = [X | Y] },
+      string_tokens(Y, Opt)
+    ; { R = [] })
+  ; { R = [X | Y] },
+    string_tokens(Y, Opt)).
+
+
+end_token --> "\r\n".
+end_token --> "\n".
+end_token --> "\r".
+end_token --> [].
+
+
+separator(Opt) -->
+    { option(token_separator(Tk_Sep), Opt) },
+    [Tk_Sep].
+
+
+row([X | Y], Opt) -->
+  field(X, Opt),
+  !,
+  ( separator(Opt) ->
+    row(Y, Opt)
+  ; end_token ->
+    { Y = [] }).
+
+
+rows(R, Opt) -->
+  row(X, Opt),
+  !,
+  ( { X \== [[]] } ->
+    rows(Y, Opt),
+    { R = [X | Y] }
+  ; { R = [] }).
+
+
+parse_csv(frame(Header, Rows), Opt) --> 
+  { option_extends(Opt, [
+      with_header(true),
+      token_separator(',')
+    ], Opt0)
+  },
+  ( { option(with_header(With_Header), Opt0),
+      With_Header == true } ->
+    row(Header, Opt0),
+    { Header \== [[]] },
+    end_token
+  ; { Header = [] }),
+  rows(Rows, Opt0).
+parse_csv(R) -->
+  parse_csv(R, []).

src/lib/dcgs.pl

@@ -1,14 +1,11 @@
-:- op(1200, xfx, -->).
-% :- op(1105, xfy, ('|')).
-
-:- module(dcgs, [phrase/2, phrase/3]).
+:- module(dcgs,
+          [op(1105, xfy, '|'),
+		   phrase/2,
+		   phrase/3]).
 
+:- use_module(library(error)).
 :- use_module(library(lists), [append/3]).
 
-user:term_expansion(Term0, (Head :- Body)) :-
-    dcg_rule(Term0, Term),
-    Term = (Head :- Body).
-
 phrase(GRBody, S0) :-
     phrase(GRBody, S0, []).
 
@@ -31,10 +28,10 @@ phrase_((A -> B ; C), S0, S) :-
     ).
 phrase_((A ; B), S0, S) :-
     (  phrase(A, S0, S) ; phrase(B, S0, S)  ).
-%% phrase_((A | B), S0, S) :-
-%%     (  phrase(A, S0, S) ; phrase(B, S0, S)  ).
+phrase_((A | B), S0, S) :-
+    (  phrase(A, S0, S) ; phrase(B, S0, S)  ).
 phrase_({G}, S0, S) :-
-    (  G, S0 = S  ).
+    (  call(G), S0 = S  ).
 phrase_(call(G), S0, S) :-
     call(G, S0, S).
 phrase_((A -> B), S0, S) :-
@@ -44,6 +41,17 @@ phrase_(phrase(NonTerminal), S0, S) :-
 phrase_([T|Ts], S0, S) :-
     append([T|Ts], S, S0).
 
+% The same version of the below two dcg_rule clauses, but with module scoping.
+dcg_rule(( M:NonTerminal, Terminals --> GRBody ), ( M:Head :- Body )) :-
+    dcg_non_terminal(NonTerminal, S0, S, Head),
+    dcg_body(GRBody, S0, S1, Goal1),
+    dcg_terminals(Terminals, S, S1, Goal2),
+    Body = ( Goal1, Goal2 ).
+dcg_rule(( M:NonTerminal --> GRBody ), ( M:Head :- Body )) :-
+    NonTerminal \= ( _, _ ),
+    dcg_non_terminal(NonTerminal, S0, S, Head),
+    dcg_body(GRBody, S0, S, Body).
+
 % This program uses append/3 as defined in the Prolog prologue.
 % Expands a DCG rule into a Prolog rule, when no error condition applies.
 dcg_rule(( NonTerminal, Terminals --> GRBody ), ( Head :- Body )) :-
@@ -84,7 +92,7 @@ dcg_constr([]). % 7.14.1
 dcg_constr([_|_]). % 7.14.2 - terminal sequence
 dcg_constr(( _, _ )). % 7.14.3 - concatenation
 dcg_constr(( _ ; _ )). % 7.14.4 - alternative
-%% dcg_constr(( _'|'_ )). % 7.14.6 - alternative
+dcg_constr(( _'|'_ )). % 7.14.6 - alternative
 dcg_constr({_}). % 7.14.7
 dcg_constr(call(_)). % 7.14.8
 dcg_constr(phrase(_)). % 7.14.9
@@ -96,6 +104,7 @@ dcg_constr((_->_)). % 7.14.12 - if-then (existence implementation dep.)
 % the construct to be expanded.
 dcg_cbody([], S0, S, S0 = S).
 dcg_cbody([T|Ts], S0, S, Goal) :-
+    must_be(list, [T|Ts]),
     dcg_terminals([T|Ts], S0, S, Goal).
 dcg_cbody(( GRFirst, GRSecond ), S0, S, ( First, Second )) :-
     dcg_body(GRFirst, S0, S1, First),
@@ -108,9 +117,9 @@ dcg_cbody(( GRCond ; GRElse ), S0, S, ( Cond ; Else )) :-
     subsumes_term(( _GRIf -> _GRThen ), GRCond),
     dcg_cbody(GRCond, S0, S, Cond),
     dcg_body(GRElse, S0, S, Else).
-%% dcg_cbody(( GREither '|' GROr ), S0, S, ( Either ; Or )) :-
-%%     dcg_body(GREither, S0, S, Either),
-%%     dcg_body(GROr, S0, S, Or).
+dcg_cbody(( GREither '|' GROr ), S0, S, ( Either ; Or )) :-
+    dcg_body(GREither, S0, S, Either),
+    dcg_body(GROr, S0, S, Or).
 dcg_cbody({Goal}, S0, S, ( Goal, S0 = S )).
 dcg_cbody(call(Cont), S0, S, call(Cont, S0, S)).
 dcg_cbody(phrase(Body), S0, S, phrase(Body, S0, S)).
@@ -119,3 +128,8 @@ dcg_cbody(\+ GRBody, S0, S, ( \+ phrase(GRBody,S0,_), S0 = S )).
 dcg_cbody(( GRIf -> GRThen ), S0, S, ( If -> Then )) :-
     dcg_body(GRIf, S0, S1, If),
     dcg_body(GRThen, S1, S, Then).
+
+user:term_expansion(Term0, Term) :-
+    nonvar(Term0),
+    dcg_rule(Term0, (Head :- Body)),
+    Term = (Head :- Body).

src/lib/debug.pl

@@ -0,0 +1,22 @@
+% Source: https://stackoverflow.com/a/30791637
+
+:- module(debug, [
+    op(900, fx, $),
+    op(900, fx, $-),
+    op(950, fy, *),
+    (*)/1,
+    ($)/1,
+    ($-)/1
+]).
+
+:- use_module(library(format), [portray_clause/1]).
+
+$-(G_0) :-
+   catch(G_0, Ex, ( portray_clause(exception:Ex:G_0), throw(Ex) ) ).
+
+$(G_0) :-
+   portray_clause(call:G_0),
+   $-G_0,
+   portray_clause(exit:G_0).
+
+*(_).

src/lib/dif.pl

@@ -51,4 +51,5 @@ gather_dif_goals([(X \== Y) | Goals]) -->
 
 attribute_goals(X) -->
     { get_atts(X, +dif(Goals)) },
-    gather_dif_goals(Goals).
+    gather_dif_goals(Goals),
+    { put_atts(X, -dif(_)) }.

src/lib/error.pl

@@ -1,5 +1,9 @@
 :- module(error, [must_be/2,
-                  can_be/2]).
+                  can_be/2,
+                  instantiation_error/1,
+                  domain_error/3,
+                  type_error/3
+                  ]).
 
 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    Written September 2018 by Markus Triska (triska@metalevel.at)
@@ -23,7 +27,8 @@
 
        - integer
        - atom
-       - list.
+       - list
+       - boolean
 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 
 must_be(Type, Term) :-
@@ -32,26 +37,41 @@ must_be(Type, Term) :-
 
 must_be_(Type, _) :-
         var(Type),
-        instantiation_error(Type).
+        instantiation_error(must_be/2).
+must_be_(var, Term) :-
+        (   var(Term) -> true
+        ;   throw(error(uninstantiation_error, must_be/2))
+        ).
 must_be_(integer, Term) :- check_(integer, integer, Term).
 must_be_(atom, Term)    :- check_(atom, atom, Term).
+must_be_(character, T)  :- check_(character, character, T).
 must_be_(list, Term)    :- check_(ilist, list, Term).
 must_be_(type, Term)    :- check_(type, type, Term).
+must_be_(boolean, Term) :- check_(boolean, boolean, Term).
 
 check_(Pred, Type, Term) :-
-        (   var(Term) -> instantiation_error(Term)
+        (   var(Term) -> instantiation_error(must_be/2)
         ;   call(Pred, Term) -> true
-        ;   type_error(Type, Term)
+        ;   type_error(Type, Term, must_be/2)
         ).
 
-ilist(V) :- var(V), instantiation_error(V).
+boolean(B) :- ( B == true ; B == false ).
+
+character(C) :-
+        atom(C),
+        atom_length(C, 1).
+
+ilist(V) :- var(V), instantiation_error(must_be/2).
 ilist([]).
 ilist([_|Ls]) :- ilist(Ls).
 
 type(type).
 type(integer).
 type(atom).
+type(character).
 type(list).
+type(var).
+type(boolean).
 
 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    can_be(Type, Term)
@@ -71,12 +91,14 @@ can_be(Type, Term) :-
         must_be(type, Type),
         (   var(Term) -> true
         ;   can_(Type, Term) -> true
-        ;   type_error(Type, Term)
+        ;   type_error(Type, Term, can_be/2)
         ).
 
 can_(integer, Term) :- integer(Term).
 can_(atom, Term)    :- atom(Term).
+can_(character, T)  :- character(T).
 can_(list, Term)    :- list_or_partial_list(Term).
+can_(boolean, Term) :- boolean(Term).
 
 list_or_partial_list(Var) :- var(Var).
 list_or_partial_list([]).
@@ -87,11 +109,11 @@ list_or_partial_list([_|Ls]) :-
    Shorthands for throwing ISO errors.
 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 
-instantiation_error(_Term) :-
-    throw(error(instantiation_error, _)).
+instantiation_error(Context) :-
+    throw(error(instantiation_error, Context)).
 
-domain_error(Type, Term) :-
-    throw(error(domain_error(Type, Term), _)).
+domain_error(Type, Term, Context) :-
+    throw(error(domain_error(Type, Term), Context)).
 
-type_error(Type, Term) :-
-    throw(error(type_error(Type, Term), _)).
+type_error(Type, Term, Context) :-
+    throw(error(type_error(Type, Term), Context)).

src/lib/files.pl

@@ -0,0 +1,200 @@
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   Written June 2020 by Markus Triska (triska@metalevel.at)
+   Part of Scryer Prolog.
+
+   Predicates for reasoning about files and directories.
+
+   In this library, directories and files are represented as
+   *lists of characters*. This is an ideal representation:
+
+   -) Lists of characters can be conveniently reasoned about with DCGs
+      and built-in Prolog predicates from library(lists). This alone
+      is already a very compelling argument to use them.
+   -) Other Scryer libraries such as library(http/http_open) also already
+      use lists of characters to represent paths.
+   -) File names are mostly ephemeral, so it is good for efficiency
+      that they can quickly allocated transiently on the heap, leaving the
+      atom table mostly unaffected. Indexing is almost never needed
+      for file names. If needed, it should be added to the engine.
+   -) The previous point is also good for security, since the system
+      leaves little trace of which files were even accessed.
+   -) Scryer Prolog represents lists of characters extremely compactly.
+
+   Some Prolog programmers will likely find this representation quite
+   unusual, because files are represented as *atoms* in many systems.
+
+   However, the ISO standard only demands that sources and sinks be
+   *ground* terms, so lists of characters are completely admissible:
+
+       A source/sink is specified as an implementation defined
+       ground term in a call of open/4 (8.11.5). All subsequent
+       references to the source/sink are made by referring to a
+       stream-term (7.10.2) or alias (7.10.2.2).
+
+   I believe that with the advent of Scryer Prolog and its efficient
+   representation of strings as lists of characters, we should take
+   this opportunity for improvement, and in fact extend the use of
+   lists of characters also to other predicates like open/3.
+
+   Please note that we *cannot* simply accept *both* representations,
+   because that would invalidate the type errors raised by this library,
+   and make future extensions for type checking impossible.
+
+   So I ask you: Please try out this representation for a few months.
+   It simplifies working with files considerably. Once we have collected
+   more experience with this representations, please let us consider
+   how to proceed in such a way that we can call it an improvement.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+:- module(files, [directory_files/2,
+                  file_size/2,
+                  file_exists/1,
+                  directory_exists/1,
+                  delete_file/1,
+                  make_directory/1,
+                  working_directory/2,
+                  path_canonical/2,
+                  path_segments/2,
+                  file_modification_time/2,
+                  file_creation_time/2,
+                  file_access_time/2]).
+
+:- use_module(library(error)).
+:- use_module(library(lists)).
+:- use_module(library(charsio)).
+
+list_of_chars(Cs) :-
+        must_be(list, Cs),
+        maplist(must_be(character), Cs).
+
+directory_files(Directory, Files) :-
+        list_of_chars(Directory),
+        can_be(list, Files),
+        '$directory_files'(Directory, Files).
+
+file_size(File, Size) :-
+        list_of_chars(File),
+        can_be(integer, Size),
+        '$file_size'(File, Size).
+
+file_exists(File) :-
+        list_of_chars(File),
+        '$file_exists'(File).
+
+directory_exists(Directory) :-
+        list_of_chars(Directory),
+        '$directory_exists'(Directory).
+
+make_directory(Directory) :-
+        list_of_chars(Directory),
+        '$make_directory'(Directory).
+
+delete_file(File) :-
+        list_of_chars(File),
+        '$delete_file'(File).
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   Dir0 is the current working directory, and the working directory
+   is changed to Dir.
+
+   Use working_directory(Ds, Ds) to determine the current working directory,
+   and leave it as is.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+working_directory(Dir0, Dir) :-
+        can_be(list, Dir0),
+        can_be(list, Dir),
+        '$working_directory'(Dir0, Dir).
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   True iff Cs is the canonical, absolute path of Ps.
+
+   All intermediate components are normalized, and all symbolic links
+   are resolved.
+
+   The predicate fails in the following situations, though not
+   necessarily *only* in these cases:
+
+      1. Ps is a path that does not exist.
+      2. A non-final component in Ps is not a directory.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+path_canonical(Ps, Cs) :-
+        must_be(list, Ps),
+        maplist(must_be(character), Ps),
+        can_be(list, Cs),
+        '$path_canonical'(Ps, Cs).
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   T is, respectively, the modification, access or creation time of File.
+   T is a time stamp, suitable for use in format_time//2 in library(time).
+
+   For two time stamps A and B, if A precedes B, then A @< B holds.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+file_modification_time(File, T) :-
+        file_time_(File, modification, T).
+
+file_access_time(File, T) :-
+        file_time_(File, access, T).
+
+file_creation_time(File, T) :-
+        file_time_(File, creation, T).
+
+file_time_(File, Which, T) :-
+        '$file_time'(File, Which, T0),
+        read_term_from_chars(T0, T).
+
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   path_segments(Ps, Segments): True iff Segments are the segments of Ps.
+
+   Segments is the list of components of the path Ps that are
+   separated by the platform-specific directory separator. Each
+   segment is a list of characters.
+
+   At least one of the arguments must be instantiated.
+
+   Examples:
+
+      ?- path_segments("/hello/there", Segments).
+         Segments = [[],"hello","there"]
+      ;  false.
+
+      ?- path_segments(Path, ["hello","there"]).
+         Path = "hello/there"
+      ;  false.
+
+
+   To obtain the platform-specific directory separator, you can use:
+
+      ?- path_segments(Separator, ["",""]).
+         Separator = "/"
+      ;  false.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+path_segments(Path, Segments) :-
+        '$directory_separator'(Sep),
+        (   var(Path) ->
+            must_be(list, Segments),
+            maplist(list_of_chars, Segments),
+            append_with_separator(Segments, Sep, Path)
+        ;   list_of_chars(Path),
+            path_to_segments(Path, Sep, Segments)
+        ).
+
+append_with_separator([], _, []).
+append_with_separator([Segment|Segments], Sep, Path) :-
+        append_with_separator_(Segments, Segment, Sep, Path).
+
+append_with_separator_([], Segment, _, Segment).
+append_with_separator_([Segment|Segments], Prev, Sep, Path) :-
+        append(Prev, [Sep|Rest], Path),
+        append_with_separator_(Segments, Segment, Sep, Rest).
+
+path_to_segments(Path, Sep, Segments) :-
+        (   append(Front, [Sep|Ps], Path) ->
+            Segments = [Front|Rest],
+            path_to_segments(Ps, Sep, Rest)
+        ;   Segments = [Path]
+        ).

src/lib/format.pl

@@ -0,0 +1,580 @@
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   Written March 2020 by Markus Triska (triska@metalevel.at)
+   Part of Scryer Prolog.
+
+   This library provides the nonterminal format_//2 to describe
+   formatted strings. format/[2,3] are provided for impure output.
+
+   Usage:
+   ======
+
+   phrase(format_(FormatString, Arguments), Ls)
+
+   format_//2 describes a list of characters Ls that are formatted
+   according to FormatString. FormatString is a string (i.e.,
+   a list of characters) that specifies the layout of Ls.
+   The characters in FormatString are used literally, except
+   for the following tokens with special meaning:
+
+     ~w    use the next available argument from Arguments here
+     ~q    use the next argument here, formatted as by writeq/1
+     ~a    use the next argument here, which must be an atom
+     ~s    use the next argument here, which must be a string
+     ~d    use the next argument here, which must be an integer
+     ~f    use the next argument here, a floating point number
+     ~Nf   where N is an integer: format the float argument
+           using N digits after the decimal point
+     ~Nd   like ~d, placing the last N digits after a decimal point;
+           if N is 0 or omitted, no decimal point is used.
+     ~ND   like ~Nd, separating digits to the left of the decimal point
+           in groups of three, using the character "," (comma)
+     ~Nr   where N is an integer between 2 and 36: format the
+           next argument, which must be an integer, in radix N.
+           The characters "a" to "z" are used for radices 10 to 36.
+     ~NR   like ~Nr, except that "A" to "Z" are used for radices > 9
+     ~|    place a tab stop at this position
+     ~N|   where N is an integer: place a tab stop at text column N
+     ~N+   where N is an integer: place a tab stop N characters
+           after the previous tab stop (or start of line)
+     ~t    distribute spaces evenly between the two closest tab stops
+     ~`Ct  like ~t, use character C instead of spaces to fill the space
+     ~n    newline
+     ~Nn   N newlines
+     ~i    ignore the next argument
+     ~~    the literal ~
+
+   Instead of ~N, you can write ~* to use the next argument from Arguments
+   as the numeric argument.
+
+   The predicate format/2 is like format_//2, except that it outputs
+   the text on the terminal instead of describing it declaratively.
+
+   format/3, used as format(Stream, FormatString, Arguments), outputs
+   the described string to the given Stream. If Stream is a binary
+   stream, then the code of each emitted character must be in 0..255.
+
+   If at all possible, format_//2 should be used, to stress pure parts
+   that enable easy testing etc. If necessary, you can emit the list Ls
+   with maplist(write, Ls).
+
+   The entire library only works if the Prolog flag double_quotes
+   is set to chars, the default value in Scryer Prolog. This should
+   also stay that way, to encourage a sensible environment.
+
+   Example:
+
+   ?- phrase(format_("~s~n~`.t~w!~12|", ["hello",there]), Cs).
+   %@    Cs = "hello\n......there!"
+   %@ ;  false.
+
+   I place this code in the public domain. Use it in any way you want.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+:- module(format, [format_//2,
+                   format/2,
+                   format/3,
+                   portray_clause/1,
+                   portray_clause/2,
+                   listing/1
+                  ]).
+
+:- use_module(library(dcgs)).
+:- use_module(library(lists)).
+:- use_module(library(error)).
+:- use_module(library(charsio)).
+:- use_module(library(between)).
+
+format_(Fs, Args) -->
+        { must_be(list, Fs),
+          must_be(list, Args),
+          phrase(cells(Fs,Args,0,[]), Cells) },
+        format_cells(Cells).
+
+format_cells([]) --> [].
+format_cells([Cell|Cells]) -->
+        format_cell(Cell),
+        format_cells(Cells).
+
+format_cell(newline) --> "\n".
+format_cell(cell(From,To,Es)) -->
+        % distribute the space between the glue elements
+        { phrase(elements_gluevars(Es, 0, Length), Vs),
+          (   Vs = [] -> true
+          ;   Space is To - From - Length,
+              (   Space =< 0 -> maplist(=(0), Vs)
+              ;   length(Vs, NumGlue),
+                  Distr is Space // NumGlue,
+                  Delta is Space - Distr*NumGlue,
+                  (   Delta =:= 0 ->
+                      maplist(=(Distr), Vs)
+                  ;   BigGlue is Distr + Delta,
+                      reverse(Vs, [BigGlue|Rest]),
+                      maplist(=(Distr), Rest)
+                  )
+              )
+          ) },
+        format_elements(Es).
+
+format_elements([]) --> [].
+format_elements([E|Es]) -->
+        format_element(E),
+        format_elements(Es).
+
+format_element(chars(Cs)) --> list(Cs).
+format_element(glue(Fill,Num)) -->
+        { length(Ls, Num),
+          maplist(=(Fill), Ls) },
+        list(Ls).
+
+list([]) --> [].
+list([L|Ls]) --> [L], list(Ls).
+
+elements_gluevars([], N, N) --> [].
+elements_gluevars([E|Es], N0, N) -->
+        element_gluevar(E, N0, N1),
+        elements_gluevars(Es, N1, N).
+
+element_gluevar(chars(Cs), N0, N) -->
+        { length(Cs, L),
+          N is N0 + L }.
+element_gluevar(glue(_,V), N, N) --> [V].
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   Our key datastructure is a list of cells and newlines.
+   A cell has the shape from_to(From,To,Elements), where
+   From and To denote the positions of surrounding tab stops.
+
+   Elements is a list of elements that occur in a cell,
+   namely terms of the form chars(Cs) and glue(Char, Var).
+   "glue" elements (TeX terminology) are evenly stretched
+   to fill the remaining whitespace in the cell. For each
+   glue element, the character Char is used for filling,
+   and Var is a free variable that is used when the
+   available space is distributed.
+
+   newline is used if ~n occurs in a format string.
+   It is is used because a newline character does not
+   consume whitespace in the sense of format strings.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+cells([], Args, Tab, Es) -->
+        (   { Args == [] } -> cell(Tab, Tab, Es)
+        ;   { domain_error(empty_list, Args, format_//2) }
+        ).
+cells([~,~|Fs], Args, Tab, Es) --> !,
+        cells(Fs, Args, Tab, [chars("~")|Es]).
+cells([~,w|Fs], [Arg|Args], Tab, Es) --> !,
+        { write_term_to_chars(Arg, [], Chars) },
+        cells(Fs, Args, Tab, [chars(Chars)|Es]).
+cells([~,q|Fs], [Arg|Args], Tab, Es) --> !,
+        { write_term_to_chars(Arg, [quoted(true)], Chars) },
+        cells(Fs, Args, Tab, [chars(Chars)|Es]).
+cells([~,a|Fs], [Arg|Args], Tab, Es) --> !,
+        { atom_chars(Arg, Chars) },
+        cells(Fs, Args, Tab, [chars(Chars)|Es]).
+cells([~|Fs0], Args0, Tab, Es) -->
+        { numeric_argument(Fs0, Num, [d|Fs], Args0, [Arg0|Args]) },
+        !,
+        { Arg is Arg0, % evaluate compound expression
+          must_be(integer, Arg),
+          number_chars(Arg, Cs0) },
+        (   { Num =:= 0 } -> { Cs = Cs0 }
+        ;   { length(Cs0, L),
+              (   L =< Num ->
+                  Delta is Num - L,
+                  length(Zs, Delta),
+                  maplist(=('0'), Zs),
+                  phrase(("0.",list(Zs),list(Cs0)), Cs)
+              ;   BeforeComma is L - Num,
+                  length(Bs, BeforeComma),
+                  append(Bs, Ds, Cs0),
+                  phrase((list(Bs),".",list(Ds)), Cs)
+              ) }
+        ),
+        cells(Fs, Args, Tab, [chars(Cs)|Es]).
+cells([~|Fs0], Args0, Tab, Es) -->
+        { numeric_argument(Fs0, Num, ['D'|Fs], Args0, [Arg|Args]) },
+        !,
+        { number_chars(Num, NCs),
+          phrase(("~",list(NCs),"d"), FStr),
+          phrase(format_(FStr, [Arg]), Cs0),
+          phrase(upto_what(Bs0, .), Cs0, Ds),
+          reverse(Bs0, Bs1),
+          phrase(groups_of_three(Bs1), Bs2),
+          reverse(Bs2, Bs),
+          append(Bs, Ds, Cs) },
+        cells(Fs, Args, Tab, [chars(Cs)|Es]).
+cells([~,i|Fs], [_|Args], Tab, Es) --> !,
+        cells(Fs, Args, Tab, Es).
+cells([~,n|Fs], Args, Tab, Es) --> !,
+        cell(Tab, Tab, Es),
+        n_newlines(1),
+        cells(Fs, Args, 0, []).
+cells([~|Fs0], Args0, Tab, Es) -->
+        { numeric_argument(Fs0, Num, [n|Fs], Args0, Args) },
+        !,
+        cell(Tab, Tab, Es),
+        n_newlines(Num),
+        cells(Fs, Args, 0, []).
+cells([~,s|Fs], [Arg|Args], Tab, Es) --> !,
+        cells(Fs, Args, Tab, [chars(Arg)|Es]).
+cells([~,f|Fs], [Arg|Args], Tab, Es) --> !,
+        { format_number_chars(Arg, Chars) },
+        cells(Fs, Args, Tab, [chars(Chars)|Es]).
+cells([~|Fs0], Args0, Tab, Es) -->
+        { numeric_argument(Fs0, Num, [f|Fs], Args0, [Arg|Args]) },
+        !,
+        { format_number_chars(Arg, Cs0),
+          phrase(upto_what(Bs, .), Cs0, Cs),
+          (   Num =:= 0 -> Chars = Bs
+          ;   (   Cs = ['.'|Rest] ->
+                  length(Rest, L),
+                  (   Num < L ->
+                      length(Ds, Num),
+                      append(Ds, _, Rest)
+                  ;   Num =:= L ->
+                      Ds = Rest
+                  ;   Num > L,
+                      Delta is Num - L,
+                      % we should look into the float with
+                      % greater accuracy here, and use the
+                      % actual digits instead of 0.
+                      length(Zs, Delta),
+                      maplist(=('0'), Zs),
+                      append(Rest, Zs, Ds)
+                  )
+              ;   length(Ds, Num),
+                  maplist(=('0'), Ds)
+              ),
+              append(Bs, ['.'|Ds], Chars)
+          ) },
+        cells(Fs, Args, Tab, [chars(Chars)|Es]).
+cells([~|Fs0], Args0, Tab, Es) -->
+        { numeric_argument(Fs0, Num, [r|Fs], Args0, [Arg|Args]) },
+        !,
+        { integer_to_radix(Arg, Num, lowercase, Cs) },
+        cells(Fs, Args, Tab, [chars(Cs)|Es]).
+cells([~|Fs0], Args0, Tab, Es) -->
+        { numeric_argument(Fs0, Num, ['R'|Fs], Args0, [Arg|Args]) },
+        !,
+        { integer_to_radix(Arg, Num, uppercase, Cs) },
+        cells(Fs, Args, Tab, [chars(Cs)|Es]).
+cells([~,'`',Char,t|Fs], Args, Tab, Es) --> !,
+        cells(Fs, Args, Tab, [glue(Char,_)|Es]).
+cells([~,t|Fs], Args, Tab, Es) --> !,
+        cells(Fs, Args, Tab, [glue(' ',_)|Es]).
+cells([~|Fs0], Args0, Tab, Es) -->
+        { numeric_argument(Fs0, Num, ['|'|Fs], Args0, Args) },
+        !,
+        cell(Tab, Num, Es),
+        cells(Fs, Args, Num, []).
+cells([~|Fs0], Args0, Tab0, Es) -->
+        { numeric_argument(Fs0, Num, [+|Fs], Args0, Args) },
+        !,
+        { Tab is Tab0 + Num },
+        cell(Tab0, Tab, Es),
+        cells(Fs, Args, Tab, []).
+cells([~,C|_], _, _, _) -->
+        { atom_chars(A, [~,C]),
+          domain_error(format_string, A, format_//2) }.
+cells(Fs0, Args, Tab, Es) -->
+        { phrase(upto_what(Fs1, ~), Fs0, Fs),
+          Fs1 = [_|_] },
+        cells(Fs, Args, Tab, [chars(Fs1)|Es]).
+
+format_number_chars(N0, Chars) :-
+        N is N0, % evaluate compound expression
+        number_chars(N, Chars).
+
+n_newlines(0) --> !.
+n_newlines(N0) --> { N0 > 0, N is N0 - 1 }, [newline], n_newlines(N).
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+?- phrase(upto_what(Cs, ~), "abc~test", Rest).
+Cs = [a,b,c], Rest = [~,t,e,s,t].
+?- phrase(upto_what(Cs, ~), "abc", Rest).
+Cs = [a,b,c], Rest = [].
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+upto_what([], W), [W] --> [W], !.
+upto_what([C|Cs], W) --> [C], !, upto_what(Cs, W).
+upto_what([], _) --> [].
+
+groups_of_three([A,B,C,D|Rs]) --> !, [A,B,C], ",", groups_of_three([D|Rs]).
+groups_of_three(Ls) --> list(Ls).
+
+cell(From, To, Es0) -->
+        (   { Es0 == [] } -> []
+        ;   { reverse(Es0, Es) },
+            [cell(From,To,Es)]
+        ).
+
+%?- numeric_argument("2f", Num, ['f'|Fs], Args0, Args).
+
+%?- numeric_argument("100b", Num, Rs, Args0, Args).
+
+numeric_argument(Ds, Num, Rest, Args0, Args) :-
+        (   Ds = [*|Rest] ->
+            Args0 = [Num|Args]
+        ;   numeric_argument_(Ds, [], Ns, Rest),
+            foldl(pow10, Ns, 0-0, Num-_),
+            Args0 = Args
+        ).
+
+numeric_argument_([D|Ds], Ns0, Ns, Rest) :-
+        (   member(D, "0123456789") ->
+            number_chars(N, [D]),
+            numeric_argument_(Ds, [N|Ns0], Ns, Rest)
+        ;   Ns = Ns0,
+            Rest = [D|Ds]
+        ).
+
+
+pow10(D, N0-Pow0, N-Pow) :-
+        N is N0 + D*10^Pow0,
+        Pow is Pow0 + 1.
+
+integer_to_radix(I0, R, Which, Cs) :-
+        I is I0, % evaluate compound expression
+        must_be(integer, I),
+        must_be(integer, R),
+        (   \+ between(2, 36, R) ->
+            domain_error(radix, R, format_//2)
+        ;   true
+        ),
+        digits(Which, Ds),
+        (   I < 0 ->
+            Pos is abs(I),
+            phrase(integer_to_radix_(Pos, R, Ds), Cs0, "-")
+        ;   I =:= 0 -> Cs0 = "0"
+        ;   phrase(integer_to_radix_(I, R, Ds), Cs0)
+        ),
+        reverse(Cs0, Cs).
+
+integer_to_radix_(0, _, _) --> !.
+integer_to_radix_(I0, R, Ds) -->
+        { M is I0 mod R,
+          nth0(M, Ds, D),
+          I is I0 // R
+          },
+        [D],
+        integer_to_radix_(I, R, Ds).
+
+digits(lowercase, "0123456789abcdefghijklmnopqrstuvwxyz").
+digits(uppercase, "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ").
+
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   Impure I/O, implemented as a small wrapper over format_//2.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+format(Fs, Args) :-
+        current_output(Stream),
+        format(Stream, Fs, Args).
+
+format(Stream, Fs, Args) :-
+        phrase(format_(Fs, Args), Cs),
+        % we use a specialised internal predicate that uses only a
+        % single "write" operation for efficiency. It is equivalent to
+        % maplist(put_char(Stream), Cs). It also works for binary streams.
+        '$put_chars'(Stream, Cs),
+        flush_output(Stream).
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+?- phrase(cells("hello", [], 0, []), Cs).
+
+?- phrase(cells("hello~10|", [], 0, []), Cs).
+?- phrase(cells("~ta~t~10|", [], 0, []), Cs).
+
+?- phrase(format_("~`at~50|", []), Ls).
+
+?- phrase(cells("~`at~50|", [], 0, []), Cs),
+   phrase(format_cells(Cs), Ls).
+?- phrase(cells("~ta~t~tb~tc~21|", [], 0, []), Cs).
+Cs = [cell(0,21,[glue(' ',_38),chars([a]),glue(' ',_62),glue(' ',_67),chars([b]),glue(' ',_91),chars([c])])].
+?- phrase(cells("~ta~t~4|", [], 0, []), Cs).
+Cs = [cell(0,4,[glue(' ',_38),chars([a]),glue(' ',_62)])].
+
+?- phrase(format_cell(cell(0,1,[glue(a,_94)])), Ls).
+
+?- phrase(format_cell(cell(0,50,[chars("hello")])), Ls).
+
+?- phrase(format_("~`at~50|~n", []), Ls).
+?- phrase(format_("hello~n~tthere~6|", []), Ls).
+
+?- format("~ta~t~4|", []).
+ a     true
+;  false.
+
+?- format("~ta~tb~tc~10|", []).
+  a  b   c   true
+;  false.
+
+?- format("~tabc~3|", []).
+
+?- format("~ta~t~4|", []).
+
+?- format("~ta~t~tb~tc~20|", []).
+    a        b     c   true
+;  false.
+
+?- format("~2f~n", [3]).
+3.00
+   true
+
+?- format("~20f", [0.1]).
+0.10000000000000000000   true % this should use higher accuracy!
+;  false.
+
+?- X is atan(2), format("~7f~n", [X]).
+1.1071487
+   X = 1.1071487177940906
+
+?- format("~`at~50|~n", []).
+aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+   true
+
+?- format("~t~N", []).
+
+?- format("~q", [.]).
+'.'   true
+
+?- format("~12r", [300]).
+210   true
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   We also provide rudimentary versions of portray_clause/1 and listing/1.
+
+   In the eventual library organization, portray_clause/1 and
+   related predicates may be placed in their own dedicated library.
+
+   portray_clause/1 is useful for printing solutions in such a way
+   that they can be read back with read/1.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+portray_clause(Term) :-
+        current_output(Out),
+        portray_clause(Out, Term).
+
+portray_clause(Stream, Term) :-
+        phrase(portray_clause_(Term), Ls),
+        format(Stream, "~s", [Ls]).
+
+portray_clause_(Term) -->
+        { term_variables(Term, Vs),
+          foldl(var_name, Vs, VNs, 0, _) },
+        portray_(Term, VNs), ".\n".
+
+var_name(V, Name=V, Num0, Num) :-
+        charsio:fabricate_var_name(numbervars, Name, Num0),
+        Num is Num0 + 1.
+
+literal(Lit, VNs) -->
+        { write_term_to_chars(Lit, [quoted(true),variable_names(VNs)], Ls) },
+        list(Ls).
+
+portray_(Var, VNs) --> { var(Var) }, !, literal(Var, VNs).
+portray_((Head :- Body), VNs) --> !,
+        literal(Head, VNs), " :-\n",
+        body_(Body, 0, 3, VNs).
+portray_((Head --> Body), VNs) --> !,
+        literal(Head, VNs), " -->\n",
+        body_(Body, 0, 3, VNs).
+portray_(Any, VNs) --> literal(Any, VNs).
+
+
+body_(Var, C, I, VNs) --> { var(Var) }, !,
+        indent_to(C, I),
+        literal(Var, VNs).
+body_((A,B), C, I, VNs) --> !,
+        body_(A, C, I, VNs), ",\n",
+        body_(B, 0, I, VNs).
+body_((A ; Else), C, I, VNs) --> % ( If -> Then ; Else )
+        { nonvar(A), A = (If -> Then) },
+        !,
+        indent_to(C, I),
+        "(  ",
+        { C1 is I + 3 },
+        body_(If, C1, C1, VNs), " ->\n",
+        body_(Then, 0, C1, VNs), "\n",
+        else_branch(Else, C1, I, VNs).
+body_((A;B), C, I, VNs) --> !,
+        indent_to(C, I),
+        "(  ",
+        { C1 is I + 3 },
+        body_(A, C1, C1, VNs), "\n",
+        else_branch(B, C1, I, VNs).
+body_(Goal, C, I, VNs) -->
+        indent_to(C, I), literal(Goal, VNs).
+
+
+else_branch(Else, C, I, VNs) -->
+        indent_to(0, I),
+        ";  ",
+        body_(Else, C, C, VNs), "\n",
+        indent_to(0, I),
+        ")".
+
+indent_to(CurrentColumn, Indent) -->
+        { Delta is Indent - CurrentColumn },
+        format_("~t~*|", [Delta]).
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+?- portray_clause(a).
+a.
+
+?- portray_clause((a :- b)).
+a :-
+   b.
+
+?- portray_clause((a :- b, c, d)).
+a :-
+   b,
+   c,
+   d.
+   true
+
+
+?- portray_clause([a,b,c,d]).
+"abcd".
+
+?- portray_clause(X).
+?- portray_clause((f(X) :- X)).
+
+?- portray_clause((h :- ( a -> b; c))).
+
+?- portray_clause((h :- ( (a -> x ; y) -> b; c))).
+
+?- portray_clause((h(X) :- ( (a(X) ; y(A,B)) -> b; c))).
+
+?- portray_clause((h :- (a,d;b,c) ; (b,e;d))).
+
+?- portray_clause((a :- b ; c ; d)).
+
+?- portray_clause((h :- L = '.')).
+
+?- portray_clause(-->(a, (b, {t}, d))).
+
+?- portray_clause((A :- B)).
+
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+listing(PI) :-
+        nonvar(PI),
+        (   PI = Name/Arity0 ->
+            Arity = Arity0
+        ;   PI = Name//Arity0 ->
+            Arity is Arity0 + 2
+        ;   type_error(predicate_indicator, PI, listing/1)
+        ),
+        functor(Head, Name, Arity),
+        \+ \+ clause(Head, _), % only true if there is at least one clause
+        (   clause(Head, Body),
+            (   Body == true ->
+                portray_clause(Head)
+            ;   portray_clause((Head :- Body))
+            ),
+            false
+        ;   true
+        ).

src/lib/freeze.pl

@@ -21,15 +21,8 @@ freeze(X, Goal) :-
     put_atts(Fresh, frozen(Goal)),
     Fresh = X.
 
-gather_freeze_goals(Attrs, _) -->
-    { var(Attrs) },
-    !.
-gather_freeze_goals([frozen(X) | _], Var) -->
-    [freeze(Var, X)],
-    !.
-gather_freeze_goals([_ | Attrs], Var) -->
-    gather_freeze_goals(Attrs, Var).
+attribute_goals(Var) -->
+    { get_atts(Var, frozen(Goals)),
+      put_atts(Var, -frozen(_)) },
+    [freeze(Var, Goals)].
 
-attribute_goals(X) -->
-    { '$get_attr_list'(X, Attrs) },
-    gather_freeze_goals(Attrs, X).

src/lib/gensym.pl

@@ -0,0 +1,32 @@
+:- module(gensym, [gensym/2,
+		   reset_gensym/1]).
+
+:- use_module(library(error)).
+:- use_module(library(lists)).
+:- use_module(library(iso_ext)).
+:- use_module(library(si)).
+
+gensym_key(Base, BaseKey) :-
+    atom_concat('gensym_', Base, BaseKey).
+
+append_id(Base, UniqueID, Unique) :-
+    atom_chars(Base, BaseChars),
+    number_chars(UniqueID, IDChars),
+    append(BaseChars, IDChars, AtomChars),
+    atom_chars(Unique, AtomChars).
+
+gensym(Base, Unique) :-
+    must_be(var, Unique),
+    atom_si(Base),
+    gensym_key(Base, BaseKey),
+    (  bb_get(BaseKey, UniqueID0) ->
+       UniqueID is UniqueID0 + 1,
+       bb_put(BaseKey, UniqueID),
+       append_id(Base, UniqueID, Unique)
+    ;  bb_put(BaseKey, 1),
+       append_id(Base, 1, Unique)
+    ).
+
+reset_gensym(Base) :-
+    atom_si(Base),
+    bb_put(Base, 0).

src/lib/http/http_open.pl

@@ -0,0 +1,84 @@
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   Written June 2020 by Markus Triska (triska@metalevel.at)
+   Part of Scryer Prolog.
+
+   http_open(+Address, -Stream, +Options)
+   ======================================
+
+   Yields Stream to read the body of an HTTP reply from Address.
+   Address is a list of characters, and includes the method. Both HTTP
+   and HTTPS are supported. Redirects are followed.
+
+   Currently, Options must be the empty list. Options may be
+   added in the future to give more control over the connection.
+
+   We use HTTP/1.0 until we can read chunked transfer-encoding.
+
+   Example:
+
+       ?- http_open("https://github.com/mthom/scryer-prolog", S, []).
+       %@    S = '$stream'(0x7f86f94a6cd0)
+       %@ ;  false.
+
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+:- module(http_open, [http_open/3]).
+
+:- use_module(library(sockets)).
+:- use_module(library(error)).
+:- use_module(library(format)).
+:- use_module(library(charsio)).
+:- use_module(library(dcgs)).
+:- use_module(library(lists), [member/2]).
+
+http_open(Address, Stream, Options) :-
+        must_be(list, Options),
+        must_be(list, Address),
+        once(phrase((list(SchemeCs), "://", list(Rest)), Address)),
+        atom_chars(Scheme, SchemeCs),
+        chars_host_url(Rest, Host, URL),
+        connect(Scheme, Host, Stream0),
+        format(Stream0, "\
+GET ~s HTTP/1.0\r\n\
+Host: ~w\r\n\
+User-Agent: Scryer Prolog\r\n\
+Connection: close\r\n\r\n\
+", [URL,Host]),
+        read_line_to_chars(Stream0, StatusLine, []),
+        once(phrase(("HTTP/1.",(['0']|['1'])," ",[D1]), StatusLine, _)),
+        read_header_lines(Stream0, HeaderLines),
+        handle_response(D1, HeaderLines, Stream0, Stream).
+
+list([]) --> [].
+list([L|Ls]) --> [L], list(Ls).
+
+handle_response('2', _, Stream, Stream).              % ok
+handle_response('3', HeaderLines, Stream0, Stream) :- % redirect
+        close(Stream0),
+        once((member(Line, HeaderLines),
+              phrase(("Location: ",list(Location),"\r\n"), Line))),
+        http_open(Location, Stream, []).
+
+% Status-Line = HTTP-Version SP Status-Code SP Reason-Phrase CRLF
+
+read_header_lines(Stream, Hs) :-
+        read_line_to_chars(Stream, Cs, []),
+        (   Cs == "" -> Hs = []
+        ;   Cs == "\r\n" -> Hs = []
+        ;   Hs = [Cs|Rest],
+            read_header_lines(Stream, Rest)
+        ).
+
+chars_host_url(Cs, Host, [/|Us]) :-
+        (   phrase((list(Hs),"/",list(Us)), Cs) ->
+            true
+        ;   Hs = Cs,
+            Us = []
+        ),
+        atom_chars(Host, Hs).
+
+connect(https, Host, Stream) :-
+        socket_client_open(Host:443, Stream, [tls(true)]).
+connect(http, Host, Stream) :-
+        socket_client_open(Host:80, Stream, []).
+

src/lib/iso_ext.pl

@@ -1,11 +1,13 @@
 %% for builtins that are not part of the ISO standard.
 %% must be loaded at the REPL with
 
-%% ?- use_module(library(non_iso)).
+%% ?- use_module(library(iso_ext)).
 
-:- module(non_iso, [bb_b_put/2, bb_get/2, bb_put/2, call_cleanup/2,
-		    call_with_inference_limit/3, forall/2,
-		    setup_call_cleanup/3, variant/2]).
+:- module(iso_ext, [bb_b_put/2, bb_get/2, bb_put/2, call_cleanup/2,
+                    call_with_inference_limit/3, forall/2,
+                    partial_string/1, partial_string/3,
+                    partial_string_tail/2, setup_call_cleanup/3,
+                    variant/2]).
 
 forall(Generate, Test) :-
     \+ (Generate, \+ Test).
@@ -20,9 +22,9 @@ bb_put(Key, _) :- throw(error(type_error(atom, Key), bb_put/2)).
 bb_b_put(Key, NewValue) :-
     (  '$bb_get_with_offset'(Key, OldValue, OldOffset) ->
        call_cleanup((store_global_var_with_offset(Key, NewValue) ; false),
-		    reset_global_var_at_offset(Key, OldValue, OldOffset))
-    ;  call_cleanup((store_global_var(Key, NewValue, _) ; false),
-		    reset_global_var_at_key(Key))
+                    reset_global_var_at_offset(Key, OldValue, OldOffset))
+    ;  call_cleanup((store_global_var_with_offset(Key, NewValue) ; false),
+                    reset_global_var_at_key(Key))
     ).
 
 store_global_var_with_offset(Key, Value) :- '$store_global_var_with_offset'(Key, Value).
@@ -46,10 +48,35 @@ call_cleanup(G, C) :- setup_call_cleanup(true, G, C).
 
 % setup_call_cleanup.
 
-setup_call_cleanup(S, G, C) :- '$get_b_value'(B),
-    S, '$set_cp_by_default'(B), '$get_current_block'(Bb),
-    ( '$call_with_default_policy'(var(C)) -> throw(error(instantiation_error, setup_call_cleanup/3))
-    ; '$call_with_default_policy'(scc_helper(C, G, Bb)) ).
+setup_call_cleanup(S, G, C) :-
+    '$get_b_value'(B),
+    call(S),
+    '$set_cp_by_default'(B),
+    '$get_current_block'(Bb),
+    (  '$call_with_default_policy'(var(C)) ->
+       throw(error(instantiation_error, setup_call_cleanup/3))
+    ;  '$call_with_default_policy'(scc_helper(C, G, Bb))
+    ).
+
+:- non_counted_backtracking scc_helper/3.
+scc_helper(C, G, Bb) :-
+    '$get_cp'(Cp), '$install_scc_cleaner'(C, NBb), call(G),
+    ( '$check_cp'(Cp) ->
+      '$reset_block'(Bb),
+      '$call_with_default_policy'(run_cleaners_without_handling(Cp))
+    ; '$call_with_default_policy'(true)
+    ; '$reset_block'(NBb),
+      '$fail').
+scc_helper(_, _, Bb) :-
+    '$reset_block'(Bb),
+    '$get_ball'(Ball),
+    '$call_with_default_policy'(run_cleaners_with_handling),
+    '$erase_ball',
+    '$call_with_default_policy'(throw(Ball)).
+scc_helper(_, _, _) :-
+    '$get_cp'(Cp),
+    '$call_with_default_policy'(run_cleaners_without_handling(Cp)),
+    '$fail'.
 
 :- non_counted_backtracking run_cleaners_with_handling/0.
 run_cleaners_with_handling :-
@@ -62,27 +89,14 @@ run_cleaners_with_handling :-
 
 :- non_counted_backtracking run_cleaners_without_handling/1.
 run_cleaners_without_handling(Cp) :-
-    '$get_scc_cleaner'(C), '$get_level'(B), C, '$set_cp_by_default'(B),
+    '$get_scc_cleaner'(C),
+    '$get_level'(B),
+    call(C),
+    '$set_cp_by_default'(B),
     '$call_with_default_policy'(run_cleaners_without_handling(Cp)).
 run_cleaners_without_handling(Cp) :-
-    '$set_cp_by_default'(Cp), '$restore_cut_policy'.
-
-:- non_counted_backtracking scc_helper/3.
-scc_helper(C, G, Bb) :-
-    '$get_cp'(Cp), '$install_scc_cleaner'(C, NBb), call(G),
-    ( '$check_cp'(Cp) -> '$reset_block'(Bb),
-			 '$call_with_default_policy'(run_cleaners_without_handling(Cp))
-    ; '$call_with_default_policy'(true)
-    ; '$reset_block'(NBb), '$fail').
-scc_helper(_, _, Bb) :-
-    '$reset_block'(Bb), '$get_ball'(Ball),
-    '$call_with_default_policy'(run_cleaners_with_handling),
-    '$erase_ball',
-    '$call_with_default_policy'(throw(Ball)).
-scc_helper(_, _, _) :-
-    '$get_cp'(Cp),
-    '$call_with_default_policy'(run_cleaners_without_handling(Cp)),
-    '$fail'.
+    '$set_cp_by_default'(Cp),
+    '$restore_cut_policy'.
 
 % call_with_inference_limit
 
@@ -119,9 +133,31 @@ call_with_inference_limit(G, L, R, Bb, B) :-
 call_with_inference_limit(_, _, R, Bb, B) :-
     '$reset_block'(Bb),
     '$remove_inference_counter'(B, _),
-    ( '$get_ball'(Ball), '$get_level'(Cp), '$set_cp_by_default'(Cp)
-    ; '$remove_call_policy_check'(B), '$fail' ),
+    (  '$get_ball'(Ball),
+       '$get_level'(Cp),
+       '$set_cp_by_default'(Cp)
+    ;  '$remove_call_policy_check'(B),
+       '$fail'
+    ),
     '$erase_ball',
     '$call_with_default_policy'(handle_ile(B, Ball, R)).
 
 variant(X, Y) :- '$variant'(X, Y).
+
+partial_string(String, L, L0) :-
+    (  String == [] ->
+       L = L0
+    ;  catch(atom_chars(Atom, String),
+         error(E, _),
+         throw(error(E, partial_string/3))),
+       '$create_partial_string'(Atom, L, L0)
+    ).
+
+partial_string(String) :-
+    '$is_partial_string'(String).
+
+partial_string_tail(String, Tail) :-
+    (  partial_string(String) ->
+       '$partial_string_tail'(String, Tail)
+    ;  throw(error(type_error(partial_string, String), partial_string_tail/2))
+    ).

src/lib/lists.pl

@@ -0,0 +1,202 @@
+:- module(lists, [member/2, select/3, append/2, append/3, foldl/4, foldl/5,
+		  memberchk/2, reverse/2, length/2, maplist/2,
+		  maplist/3, maplist/4, maplist/5, maplist/6,
+		  maplist/7, maplist/8, maplist/9, same_length/2, nth0/3,
+		  sum_list/2, transpose/2, list_to_set/2]).
+
+
+:- use_module(library(error)).
+
+
+length(Xs, N) :-
+    var(N), !,
+    '$skip_max_list'(M, -1, Xs, Xs0),
+    (  Xs0 == [] -> N = M
+    ;  var(Xs0)  -> length_addendum(Xs0, N, M)).
+length(Xs, N) :-
+    integer(N),
+    N >= 0, !,
+    '$skip_max_list'(M, N, Xs, Xs0),
+    (  Xs0 == [] -> N = M
+    ;  var(Xs0)  -> R is N-M, length_rundown(Xs0, R)).
+length(_, N) :-
+    integer(N), !,
+    domain_error(not_less_than_zero, N, length/2).
+length(_, N) :-
+    type_error(integer, N, length/2).
+
+length_addendum([], N, N).
+length_addendum([_|Xs], N, M) :-
+    M1 is M + 1,
+    length_addendum(Xs, N, M1).
+
+length_rundown(Xs, 0) :- !, Xs = [].
+length_rundown([_|Xs], N) :-
+    N1 is N-1,
+    length_rundown(Xs, N1).
+
+
+member(X, [X|_]).
+member(X, [_|Xs]) :- member(X, Xs).
+
+
+select(X, [X|Xs], Xs).
+select(X, [Y|Xs], [Y|Ys]) :- select(X, Xs, Ys).
+
+
+append([], []).
+append([L0|Ls0], Ls) :-
+    append(L0, Rest, Ls),
+    append(Ls0, Rest).
+
+
+append([], R, R).
+append([X|L], R, [X|S]) :- append(L, R, S).
+
+
+memberchk(X, Xs) :- member(X, Xs), !.
+
+
+reverse(Xs, Ys) :-
+    (  nonvar(Xs) -> reverse(Xs, Ys, [], Xs)
+    ;  reverse(Ys, Xs, [], Ys)
+    ).
+
+reverse([], [], YsRev, YsRev).
+reverse([_|Xs], [Y1|Ys], YsPreludeRev, Xss) :-
+    reverse(Xs, Ys, [Y1|YsPreludeRev], Xss).
+
+
+maplist(_, []).
+maplist(Cont1, [E1|E1s]) :-
+    call(Cont1, E1),
+    maplist(Cont1, E1s).
+
+maplist(_, [], []).
+maplist(Cont2, [E1|E1s], [E2|E2s]) :-
+    call(Cont2, E1, E2),
+    maplist(Cont2, E1s, E2s).
+
+maplist(_, [], [], []).
+maplist(Cont3, [E1|E1s], [E2|E2s], [E3|E3s]) :-
+    call(Cont3, E1, E2, E3),
+    maplist(Cont3, E1s, E2s, E3s).
+
+maplist(_, [], [], [], []).
+maplist(Cont, [E1|E1s], [E2|E2s], [E3|E3s], [E4|E4s]) :-
+    call(Cont, E1, E2, E3, E4),
+    maplist(Cont, E1s, E2s, E3s, E4s).
+
+maplist(_, [], [], [], [], []).
+maplist(Cont, [E1|E1s], [E2|E2s], [E3|E3s], [E4|E4s], [E5|E5s]) :-
+    call(Cont, E1, E2, E3, E4, E5),
+    maplist(Cont, E1s, E2s, E3s, E4s, E5s).
+
+maplist(_, [], [], [], [], [], []).
+maplist(Cont, [E1|E1s], [E2|E2s], [E3|E3s], [E4|E4s], [E5|E5s], [E6|E6s]) :-
+    call(Cont, E1, E2, E3, E4, E5, E6),
+    maplist(Cont, E1s, E2s, E3s, E4s, E5s, E6s).
+
+maplist(_, [], [], [], [], [], [], []).
+maplist(Cont, [E1|E1s], [E2|E2s], [E3|E3s], [E4|E4s], [E5|E5s], [E6|E6s], [E7|E7s]) :-
+    call(Cont, E1, E2, E3, E4, E5, E6, E7),
+    maplist(Cont, E1s, E2s, E3s, E4s, E5s, E6s, E7s).
+
+maplist(_, [], [], [], [], [], [], [], []).
+maplist(Cont, [E1|E1s], [E2|E2s], [E3|E3s], [E4|E4s], [E5|E5s], [E6|E6s], [E7|E7s], [E8|E8s]) :-
+    call(Cont, E1, E2, E3, E4, E5, E6, E7, E8),
+    maplist(Cont, E1s, E2s, E3s, E4s, E5s, E6s, E7s, E8s).
+
+
+sum_list(Ls, S) :-
+        foldl(sum_, Ls, 0, S).
+
+sum_(L, S0, S) :- S is S0 + L.
+
+
+
+same_length([], []).
+same_length([_|As], [_|Bs]) :-
+        same_length(As, Bs).
+
+
+foldl(Goal_3, Ls, A0, A) :-
+        foldl_(Ls, Goal_3, A0, A).
+
+foldl_([], _, A, A).
+foldl_([L|Ls], G_3, A0, A) :-
+        call(G_3, L, A0, A1),
+        foldl_(Ls, G_3, A1, A).
+
+
+foldl(Goal_4, Xs, Ys, A0, A) :-
+        foldl_(Xs, Ys, Goal_4, A0, A).
+
+foldl_([], [], _, A, A).
+foldl_([X|Xs], [Y|Ys], G_4, A0, A) :-
+        call(G_4, X, Y, A0, A1),
+        foldl_(Xs, Ys, G_4, A1, A).
+
+transpose(Ls, Ts) :-
+        lists_transpose(Ls, Ts).
+
+lists_transpose([], []).
+lists_transpose([L|Ls], Ts) :-
+        maplist(same_length(L), Ls),
+        foldl(transpose_, L, Ts, [L|Ls], _).
+
+transpose_(_, Fs, Lists0, Lists) :-
+        maplist(list_first_rest, Lists0, Fs, Lists).
+
+list_first_rest([L|Ls], L, Ls).
+
+
+list_to_set(Ls0, Ls) :-
+        maplist(with_var, Ls0, LVs0),
+        keysort(LVs0, LVs),
+        same_elements(LVs),
+        pick_firsts(LVs0, Ls).
+
+pick_firsts([], []).
+pick_firsts([E-V|EVs], Fs0) :-
+        (   V == visited ->
+            Fs0 = Fs
+        ;   V = visited,
+            Fs0 = [E|Fs]
+        ),
+        pick_firsts(EVs, Fs).
+
+with_var(E, E-_).
+
+same_elements([]).
+same_elements([EV|EVs]) :-
+        foldl(unify_same, EVs, EV, _).
+
+unify_same(E-V, Prev-Var, E-V) :-
+        (   Prev == E ->
+            Var = V
+        ;   true
+        ).
+
+
+nth0(N, Es, E) :-
+        can_be(integer, N),
+        can_be(list, Es),
+        (   integer(N) ->
+            nth0_index(N, Es, E)
+        ;   nth0_search(N, Es, E)
+        ).
+
+nth0_index(0, [E|_], E) :- !.
+nth0_index(N, [_|Es], E) :-
+        N > 0,
+        N1 is N - 1,
+        nth0_index(N1, Es, E).
+
+nth0_search(N, Es, E) :-
+        nth0_search(0, N, Es, E).
+
+nth0_search(N, N, [E|_], E).
+nth0_search(N0, N, [_|Es], E) :-
+        N1 is N0 + 1,
+        nth0_search(N1, N, Es, E).

src/lib/os.pl

@@ -0,0 +1,58 @@
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   Predicates for reasoning about the operating system (OS) environment.
+   Written July 2020 by Markus Triska (triska@metalevel.at).
+
+   Lists of characters are used throughout to represent keys and values.
+
+   Example:
+
+       ?- getenv("LANG", Ls).
+          Ls = "en_US.UTF-8"
+       ;  false.
+
+   Public domain code.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+:- module(os, [getenv/2,
+               setenv/2,
+               unsetenv/1]).
+
+:- use_module(library(error)).
+:- use_module(library(charsio)).
+:- use_module(library(lists)).
+
+getenv(Key, Value) :-
+        must_be_env_var(Key),
+        '$getenv'(Key, Value).
+
+setenv(Key, Value) :-
+        must_be_env_var(Key),
+        must_be_chars(Value),
+        '$setenv'(Key, Value).
+
+unsetenv(Key) :-
+        must_be_env_var(Key),
+        '$unsetenv'(Key).
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   For now, we only support a restricted subset of variable names.
+
+   The reason is that Rust may panic if a key is empty, contains an
+   ASCII equals sign '=' or the NUL character '\0', or when the value
+   contains the NUL character.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+must_be_env_var(Cs) :-
+        must_be_chars(Cs),
+        Cs = [_|_],
+        (   maplist(permitted, Cs) -> true
+        ;   domain_error(env_var, Cs, os)
+        ).
+
+permitted(C) :- char_type(C, alnum).
+permitted(C) :- char_type(C, ascii_punctuation).
+permitted('_').
+
+must_be_chars(Cs) :-
+        must_be(list, Cs),
+        maplist(must_be(character), Cs).

src/lib/pairs.pl

@@ -0,0 +1,33 @@
+:- module(pairs, [pairs_keys_values/3,
+		  pairs_keys/2,
+		  pairs_values/2,
+		  group_pairs_by_key/2,
+		  map_list_to_pairs/3]).
+
+
+pairs_keys_values([], [], []).
+pairs_keys_values([A-B|ABs], [A|As], [B|Bs]) :-
+        pairs_keys_values(ABs, As, Bs).
+
+pairs_keys(Ps, Ks) :- pairs_keys_values(Ps, Ks, _).
+
+pairs_values(Ps, Vs) :- pairs_keys_values(Ps, _, Vs).
+
+map_list_to_pairs(Pred, Ls, Ps) :-
+        map_list_to_pairs2(Ls, Pred, Ps).
+
+map_list_to_pairs2([], _, []).
+map_list_to_pairs2([H|T0], Pred, [K-H|T]) :-
+        call(Pred, H, K),
+        map_list_to_pairs2(T0, Pred, T).
+
+
+group_pairs_by_key([], []).
+group_pairs_by_key([K-V|KVs0], [K-[V|Vs]|KVs]) :-
+        same_key(K, KVs0, Vs, KVs1),
+        group_pairs_by_key(KVs1, KVs).
+
+same_key(K0, [K1-V|KVs0], [V|Vs], KVs) :-
+        K0 == K1, !,
+        same_key(K0, KVs0, Vs, KVs).
+same_key(_, KVs, [], KVs).

src/lib/pio.pl

@@ -0,0 +1,42 @@
+:- module(pio, [phrase_from_file/2,
+                phrase_from_file/3]).
+
+:- use_module(library(dcgs)).
+:- use_module(library(error)).
+:- use_module(library(freeze)).
+:- use_module(library(iso_ext), [setup_call_cleanup/3, partial_string/3]).
+:- use_module(library(lists), [member/2]).
+
+phrase_from_file(NT, File) :-
+    phrase_from_file(NT, File, []).
+
+phrase_from_file(NT, File, Options) :-
+    (   var(File) -> instantiation_error(phrase_from_file/3)
+    ;   (\+ atom(File) ; File = []) ->
+            domain_error(source_sink, File, phrase_from_file/3)
+    ;   must_be(list, Options),
+        (   member(Var, Options), var(Var) -> instantiation_error(phrase_from_file/3)
+        ;   member(type(Type), Options) ->
+            must_be(atom, Type),
+            member(Type, [text,binary])
+        ;   Type = text
+        ),
+        setup_call_cleanup(open(File, read, Stream, [reposition(true)|Options]),
+                           (   stream_to_lazy_list(Stream, Xs),
+                               phrase(NT, Xs) ),
+                           close(Stream))
+   ).
+
+
+stream_to_lazy_list(Stream, Xs) :-
+        stream_property(Stream, position(Pos)),
+        freeze(Xs, reader_step(Stream, Pos, Xs)).
+
+reader_step(Stream, Pos, Xs0) :-
+        set_stream_position(Stream, Pos),
+        (   at_end_of_stream(Stream)
+        ->  Xs0 = []
+        ;   '$get_n_chars'(Stream, 4096, Cs),
+            partial_string(Cs, Xs0, Xs),
+            stream_to_lazy_list(Stream, Xs)
+        ).

src/lib/random.pl

@@ -0,0 +1,59 @@
+:- module(random, [maybe/0, random/1, random_integer/3, set_random/1]).
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   To retain desirable declarative properties, predicates that internally
+   use random numbers should be equipped with an argument that specifies
+   the random seed. This makes everything completely reproducible.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+:- use_module(library(error)).
+
+% succeeds with probability 0.5.
+maybe :- '$maybe'.
+
+% The higher the precision, the slower it gets.
+random_number_precision(64).
+
+random(R) :-
+    var(R),
+    random_number_precision(N),
+    rnd(N, R).
+
+random_integer(Lower, Upper, R) :-
+    var(R),
+    (   (var(Lower) ; var(Upper)) ->
+            instantiation_error(random_integer/3)
+    ;   \+ integer(Lower) ->
+            domain_error(integer, Lower, random_integer/3)
+    ;   \+ integer(Upper) ->
+            domain_error(integer, Upper, random_integer/3)
+    ;   Upper > Lower,
+        random(R0),
+        R is floor((Upper - Lower) * R0 + Lower)
+    ).
+
+rnd(N, R) :-
+    rnd_(N, 0, R).
+
+rnd_(0, R, R) :- !.
+rnd_(N, R0, R) :-
+    maybe,
+    !,
+    N1 is N - 1,
+    rnd_(N1, R0, R).
+rnd_(N, R0, R) :-
+    N1 is N - 1,
+    R1 is R0 + 1.0 / 2.0 ^ N,
+    rnd_(N1, R1, R).
+
+set_random(Seed) :-
+    (   nonvar(Seed) ->
+        (  Seed = seed(S) ->
+        (  var(S) -> instantiation_error(set_random/1)
+        ;  integer(S) -> '$set_seed'(S)
+        ;  type_error(integer, S, set_random/1)
+        )
+        )
+    ;   instantiation_error(set_random/1)
+    ).
+

src/lib/sgml.pl

@@ -0,0 +1,92 @@
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   Predicates for parsing HTML and XML documents.
+   Written June 2020 by Markus Triska (triska@metalevel.at)
+   Part of Scryer Prolog.
+
+   Currently, two predicates are provided:
+
+   -  load_html(+Source, -Es, +Options)
+   -  load_xml(+Source, -Es, +Options)
+
+   These predicates parse HTML and XML documents, respectively.
+
+   Source must be a stream, specified as stream(S), or a file,
+   specified as file(Name), where Name is a list of characters, or a
+   list of characters with the document contents.
+
+   Es is unified with the abstract syntax tree of the parsed document,
+   represented as a list of elements where each is of the form:
+
+   * a list of characters, representing text
+   * element(Name, Attrs, Children)
+     - Name is the name of the tag
+     - Attrs is a list of Key=Value pairs:
+       Key is an atom, and Value is a list of characters
+     - Children is a list of elements as specified here.
+
+   Currently, Options are ignored. In the future, more options may be
+   provided to control parsing.
+
+   Example:
+
+      ?- load_html("<html><head><title>Hello!</title></head></html>", Es, []).
+
+   Yielding:
+
+         Es = [element(html,[],
+                [element(head,[],
+                  [element(title,[],
+                    ["Hello!"])]),
+                 element(body,[],[])])].
+
+   library(xpath) provides convenient reasoning about parsed documents.
+   For example, to fetch the title of the document above, we can use:
+
+      ?- load_html("<html><head><title>Hello!</title></head></html>", Es, []),
+         xpath(Es, //title(text), T).
+
+   Yielding T = "Hello!".
+
+   Use http_open/3 from library(http/http_open) to read answers from
+   web servers via streams.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+:- module(sgml, [load_html/3,
+                 load_xml/3]).
+
+:- use_module(library(iso_ext)).
+:- use_module(library(error)).
+:- use_module(library(dcgs)).
+:- use_module(library(pio)).
+
+load_html(Source, Es, Options) :-
+        load_structure_(Source, Es, Options, html).
+load_xml(Source, Es, Options) :-
+        load_structure_(Source, Es, Options, xml).
+
+list([]) --> [].
+list([L|Ls]) --> [L], list(Ls).
+
+load_structure_([], [], _, _).
+load_structure_([C|Cs], [E], Options, What) :-
+        load_(What, [C|Cs], E, Options).
+load_structure_(file(Fs), [E], Options, What) :-
+        must_be(list, Options),
+        must_be(list, Fs),
+        atom_chars(File, Fs),
+        once(phrase_from_file(list(Cs), File)),
+        load_(What, Cs, E, Options).
+load_structure_(stream(Stream), [E], Options, What) :-
+        must_be(list, Options),
+        read_to_end(Stream, Cs),
+        load_(What, Cs, E, Options).
+
+load_(html, Cs, E, Options) :- '$load_html'(Cs, E, Options).
+load_(xml, Cs, E, Options) :- '$load_xml'(Cs, E, Options).
+
+read_to_end(Stream, Cs) :-
+        '$get_n_chars'(Stream, 4096, Cs0),
+        (   Cs0 = [] -> Cs = []
+        ;   partial_string(Cs0, Cs, Rest),
+            read_to_end(Stream, Rest)
+        ).

src/lib/sockets.pl

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+
+:- module(sockets, [socket_client_open/3,
+                    socket_server_open/2,
+                    socket_server_accept/4,
+                    socket_server_close/1,
+                    current_hostname/1]).
+
+:- use_module(library(error)).
+:- use_module(library(lists)).
+
+parse_socket_options_(tls(TLS), tls-TLS) :-
+    must_be(boolean, TLS), !.
+parse_socket_options_(Option, OptionPair) :-
+    builtins:parse_stream_options_(Option, OptionPair).
+
+parse_socket_options(Options, OptionValues, Stub) :-
+    DefaultOptions = [alias-[], eof_action-eof_code, reposition-false, tls-false, type-text],
+    builtins:parse_options_list(Options, parse_socket_options_, DefaultOptions, OptionValues, Stub).
+
+socket_client_open(Addr, Stream, Options) :-
+    (  var(Addr) ->
+       throw(error(instantiation_error, socket_client_open/3))
+    ;
+       true
+    ),
+    must_be(var, Stream),
+    must_be(list, Options),
+    (  Addr = Address:Port,
+       atom(Address),
+       ( atom(Port) ; integer(Port) ) ->
+       true
+    ;
+       throw(error(type_error(socket_address, Addr), socket_client_open/3))
+    ),
+    parse_socket_options(Options,
+                         [Alias, EOFAction, Reposition, TLS, Type],
+                         socket_client_open/3),
+    '$socket_client_open'(Address, Port, Stream, Alias, EOFAction, Reposition, Type, TLS).
+
+
+socket_server_open(Addr, ServerSocket) :-
+    must_be(var, ServerSocket),
+    (  ( integer(Addr) ; var(Addr) ) ->
+       '$socket_server_open'([], Addr, ServerSocket)
+    ;
+       Addr = Address:Port,
+       must_be(atom, Address),
+       can_be(integer, Port),
+       '$socket_server_open'(Address, Port, ServerSocket)
+    ).
+
+
+socket_server_accept(ServerSocket, Client, Stream, Options) :-
+    must_be(var, Client),
+    must_be(var, Stream),
+    builtins:parse_stream_options(Options,
+                                  [Alias, EOFAction, Reposition, Type],
+                                  socket_server_accept/4),
+    '$socket_server_accept'(ServerSocket, Client, Stream, Alias, EOFAction, Reposition, Type).
+
+
+socket_server_close(ServerSocket) :-
+    '$socket_server_close'(ServerSocket).
+
+
+current_hostname(HostName) :-
+    '$current_hostname'(HostName).