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include a short overview of notable libraries

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Markus Triska
2020-03-15 11:23:17 +01:00
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README.md
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@@ -225,12 +225,64 @@ By all appearances, partial strings are plain Prolog lists.
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/prolog/lib/*.pl`](src/prolog/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 Prolog are also called
*library* modules or *libraries*, and include:
* [`lists`](src/prolog/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/prolog/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/prolog/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/prolog/lib/reif.pl)
providing `if_/3`, `tfilter/3` and related predicates
as described in *Indexing dif/2*.
* [`pairs`](src/prolog/lib/pairs.pl)
By convention, *pairs* are Prolog terms with
principal 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/prolog/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 of 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 inference*.
* [`error`](src/prolog/lib/error.pl)
`must_be/2` and `can_be/2` complement the type checks provided
by `library(si)`, and are especially useful for Prolog library
authors.
* [`tabling`](src/prolog/lib/tabling.pl)
The operator `(table)/1` is used in directives that prepare
predicates for tabled execution (SLG resolution).
* [`format`](src/prolog/lib/format.pl)
The nonterminal `format_//2` is used to describe formatted output,
arranging arguments according to a given format string.
The predicate `format/2` is provided for impure output.
* [`assoc`](src/prolog/lib/assoc.pl)
providing `empty_assoc/1`, `get_assoc/3`, `put_assoc/4` etc.
to manage elements in AVL trees which ensure
*O*(log(*N*)) access.
* [`clpb`](src/prolog/lib/clpb.pl)
CLP(B): Constraint Logic Programming over Boolean variables,
a BDD-based SAT solver provided via the predicates
`sat/1`, `taut/2`, `labeling/1` etc.
To use predicates provided by the `lists` library, write:
```
?- use_module(library(lists)).