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

Improved readline

Cargo.lock

@@ -27,6 +27,12 @@ version = "0.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cff77d8686867eceff3105329d4698d96c2391c176d5d03adc90c7389162b5b8"
 
+[[package]]
+name = "autocfg"
+version = "0.1.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1d49d90015b3c36167a20fe2810c5cd875ad504b39cff3d4eae7977e6b7c1cb2"
+
 [[package]]
 name = "autocfg"
 version = "1.0.0"
@@ -45,6 +51,27 @@ version = "0.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b41b7ea54a0c9d92199de89e20e58d49f02f8e699814ef3fdf266f6f748d15c7"
 
+[[package]]
+name = "base64"
+version = "0.12.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3441f0f7b02788e948e47f457ca01f1d7e6d92c693bc132c22b087d3141c03ff"
+
+[[package]]
+name = "bit-set"
+version = "0.5.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6e11e16035ea35e4e5997b393eacbf6f63983188f7a2ad25bfb13465f5ad59de"
+dependencies = [
+ "bit-vec",
+]
+
+[[package]]
+name = "bit-vec"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5f0dc55f2d8a1a85650ac47858bb001b4c0dd73d79e3c455a842925e68d29cd3"
+
 [[package]]
 name = "bitflags"
 version = "1.2.1"
@@ -125,6 +152,17 @@ version = "0.1.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4785bdd1c96b2a846b2bd7cc02e86b6b3dbf14e7e53446c4f54c92a361040822"
 
+[[package]]
+name = "chrono"
+version = "0.4.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "80094f509cf8b5ae86a4966a39b3ff66cd7e2a3e594accec3743ff3fabeab5b2"
+dependencies = [
+ "num-integer",
+ "num-traits 0.2.11",
+ "time",
+]
+
 [[package]]
 name = "cloudabi"
 version = "0.0.3"
@@ -140,6 +178,22 @@ version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "245097e9a4535ee1e3e3931fcfcd55a796a44c643e8596ff6566d68f09b87bbc"
 
+[[package]]
+name = "core-foundation"
+version = "0.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "57d24c7a13c43e870e37c1556b74555437870a04514f7685f5b354e090567171"
+dependencies = [
+ "core-foundation-sys",
+ "libc",
+]
+
+[[package]]
+name = "core-foundation-sys"
+version = "0.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b3a71ab494c0b5b860bdc8407ae08978052417070c2ced38573a9157ad75b8ac"
+
 [[package]]
 name = "cpu-time"
 version = "1.0.0"
@@ -156,7 +210,7 @@ version = "0.7.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c3c7c73a2d1e9fc0886a08b93e98eb643461230d5f1925e4036204d5f2e261a8"
 dependencies = [
- "autocfg",
+ "autocfg 1.0.0",
  "cfg-if",
  "lazy_static",
 ]
@@ -239,6 +293,27 @@ version = "0.10.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4bb454f0228b18c7f4c3b0ebbee346ed9c52e7443b0999cd543ff3571205701d"
 
+[[package]]
+name = "foreign-types"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f6f339eb8adc052cd2ca78910fda869aefa38d22d5cb648e6485e4d3fc06f3b1"
+dependencies = [
+ "foreign-types-shared",
+]
+
+[[package]]
+name = "foreign-types-shared"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "00b0228411908ca8685dba7fc2cdd70ec9990a6e753e89b6ac91a84c40fbaf4b"
+
+[[package]]
+name = "fuchsia-cprng"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a06f77d526c1a601b7c4cdd98f54b5eaabffc14d5f2f0296febdc7f357c6d3ba"
+
 [[package]]
 name = "fuchsia-zircon"
 version = "0.3.3"
@@ -255,6 +330,16 @@ version = "0.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3dcaa9ae7725d12cdb85b3ad99a434db70b468c09ded17e012d86b5c1010f7a7"
 
+[[package]]
+name = "futf"
+version = "0.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7c9c1ce3fa9336301af935ab852c437817d14cd33690446569392e65170aac3b"
+dependencies = [
+ "mac",
+ "new_debug_unreachable",
+]
+
 [[package]]
 name = "generic-array"
 version = "0.12.3"
@@ -292,9 +377,9 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "34a97a52fdee1870a34fa6e4b77570cba531b27d1838874fef4429a791a3d657"
 dependencies = [
  "proc-macro-hack",
- "proc-macro2",
- "quote",
- "syn",
+ "proc-macro2 1.0.10",
+ "quote 1.0.3",
+ "syn 1.0.18",
 ]
 
 [[package]]
@@ -318,13 +403,27 @@ dependencies = [
  "winapi 0.3.8",
 ]
 
+[[package]]
+name = "html5ever"
+version = "0.23.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5ce65ac8028cf5a287a7dbf6c4e0a6cf2dcf022ed5b167a81bae66ebf599a8b7"
+dependencies = [
+ "log",
+ "mac",
+ "markup5ever",
+ "proc-macro2 0.4.30",
+ "quote 0.6.13",
+ "syn 0.15.44",
+]
+
 [[package]]
 name = "indexmap"
 version = "1.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "076f042c5b7b98f31d205f1249267e12a6518c1481e9dae9764af19b707d2292"
 dependencies = [
- "autocfg",
+ "autocfg 1.0.0",
 ]
 
 [[package]]
@@ -336,6 +435,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "itoa"
+version = "0.4.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dc6f3ad7b9d11a0c00842ff8de1b60ee58661048eb8049ed33c73594f359d7e6"
+
 [[package]]
 name = "js-sys"
 version = "0.3.39"
@@ -397,6 +502,17 @@ version = "0.2.69"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "99e85c08494b21a9054e7fe1374a732aeadaff3980b6990b94bfd3a70f690005"
 
+[[package]]
+name = "libsodium-sys"
+version = "0.2.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a685b64f837b339074115f2e7f7b431ac73681d08d75b389db7498b8892b8a58"
+dependencies = [
+ "cc",
+ "libc",
+ "pkg-config",
+]
+
 [[package]]
 name = "lock_api"
 version = "0.3.4"
@@ -415,6 +531,29 @@ dependencies = [
  "cfg-if",
 ]
 
+[[package]]
+name = "mac"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c41e0c4fef86961ac6d6f8a82609f55f31b05e4fce149ac5710e439df7619ba4"
+
+[[package]]
+name = "markup5ever"
+version = "0.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f1af46a727284117e09780d05038b1ce6fc9c76cc6df183c3dae5a8955a25e21"
+dependencies = [
+ "log",
+ "phf",
+ "phf_codegen",
+ "serde",
+ "serde_derive",
+ "serde_json",
+ "string_cache",
+ "string_cache_codegen",
+ "tendril",
+]
+
 [[package]]
 name = "match_cfg"
 version = "0.1.0"
@@ -464,6 +603,24 @@ dependencies = [
  "ws2_32-sys",
 ]
 
+[[package]]
+name = "native-tls"
+version = "0.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2b0d88c06fe90d5ee94048ba40409ef1d9315d86f6f38c2efdaad4fb50c58b2d"
+dependencies = [
+ "lazy_static",
+ "libc",
+ "log",
+ "openssl",
+ "openssl-probe",
+ "openssl-sys",
+ "schannel",
+ "security-framework",
+ "security-framework-sys",
+ "tempfile",
+]
+
 [[package]]
 name = "net2"
 version = "0.2.33"
@@ -475,6 +632,12 @@ dependencies = [
  "winapi 0.3.8",
 ]
 
+[[package]]
+name = "new_debug_unreachable"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e4a24736216ec316047a1fc4252e27dabb04218aa4a3f37c6e7ddbf1f9782b54"
+
 [[package]]
 name = "nix"
 version = "0.15.0"
@@ -513,7 +676,7 @@ version = "0.2.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "090c7f9998ee0ff65aa5b723e4009f7b217707f1fb5ea551329cc4d6231fb304"
 dependencies = [
- "autocfg",
+ "autocfg 1.0.0",
  "num-integer",
  "num-traits 0.2.11",
 ]
@@ -524,7 +687,7 @@ version = "0.1.42"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3f6ea62e9d81a77cd3ee9a2a5b9b609447857f3d358704331e4ef39eb247fcba"
 dependencies = [
- "autocfg",
+ "autocfg 1.0.0",
  "num-traits 0.2.11",
 ]
 
@@ -534,7 +697,7 @@ version = "0.2.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5c000134b5dbf44adc5cb772486d335293351644b801551abe8f75c84cfa4aef"
 dependencies = [
- "autocfg",
+ "autocfg 1.0.0",
  "num-bigint",
  "num-integer",
  "num-traits 0.2.11",
@@ -568,7 +731,7 @@ version = "0.2.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c62be47e61d1842b9170f0fdeec8eba98e60e90e5446449a0545e5152acd7096"
 dependencies = [
- "autocfg",
+ "autocfg 1.0.0",
 ]
 
 [[package]]
@@ -583,6 +746,49 @@ version = "0.2.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2839e79665f131bdb5782e51f2c6c9599c133c6098982a54c794358bf432529c"
 
+[[package]]
+name = "openssl"
+version = "0.10.29"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cee6d85f4cb4c4f59a6a85d5b68a233d280c82e29e822913b9c8b129fbf20bdd"
+dependencies = [
+ "bitflags",
+ "cfg-if",
+ "foreign-types",
+ "lazy_static",
+ "libc",
+ "openssl-sys",
+]
+
+[[package]]
+name = "openssl-probe"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "77af24da69f9d9341038eba93a073b1fdaaa1b788221b00a69bce9e762cb32de"
+
+[[package]]
+name = "openssl-src"
+version = "111.9.0+1.1.1g"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a2dbe10ddd1eb335aba3780eb2eaa13e1b7b441d2562fd962398740927f39ec4"
+dependencies = [
+ "cc",
+]
+
+[[package]]
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+version = "0.9.58"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a842db4709b604f0fe5d1170ae3565899be2ad3d9cbc72dedc789ac0511f78de"
+dependencies = [
+ "autocfg 1.0.0",
+ "cc",
+ "libc",
+ "openssl-src",
+ "pkg-config",
+ "vcpkg",
+]
+
 [[package]]
 name = "ordered-float"
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@@ -617,26 +823,91 @@ dependencies = [
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 ]
 
+[[package]]
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+version = "0.7.24"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b3da44b85f8e8dfaec21adae67f95d93244b2ecf6ad2a692320598dcc8e6dd18"
+dependencies = [
+ "phf_shared",
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+
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+version = "0.7.24"
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+checksum = "b03e85129e324ad4166b06b2c7491ae27fe3ec353af72e72cd1654c7225d517e"
+dependencies = [
+ "phf_generator",
+ "phf_shared",
+]
+
+[[package]]
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+version = "0.7.24"
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+checksum = "09364cc93c159b8b06b1f4dd8a4398984503483891b0c26b867cf431fb132662"
+dependencies = [
+ "phf_shared",
+ "rand 0.6.5",
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+
+[[package]]
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+checksum = "234f71a15de2288bcb7e3b6515828d22af7ec8598ee6d24c3b526fa0a80b67a0"
+dependencies = [
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+]
+
+[[package]]
+name = "pkg-config"
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+
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+
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+[[package]]
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+dependencies = [
+ "unicode-xid 0.1.0",
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+
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 dependencies = [
- "unicode-xid",
+ "unicode-xid 0.2.0",
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 [[package]]
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-version = "0.8.59"
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@@ -645,13 +916,178 @@ dependencies = [
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+
+[[package]]
+name = "rand_os"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7b75f676a1e053fc562eafbb47838d67c84801e38fc1ba459e8f180deabd5071"
+dependencies = [
+ "cloudabi",
+ "fuchsia-cprng",
+ "libc",
+ "rand_core 0.4.2",
+ "rdrand",
+ "winapi 0.3.8",
+]
+
+[[package]]
+name = "rand_pcg"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "abf9b09b01790cfe0364f52bf32995ea3c39f4d2dd011eac241d2914146d0b44"
+dependencies = [
+ "autocfg 0.1.7",
+ "rand_core 0.4.2",
+]
+
+[[package]]
+name = "rand_xorshift"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cbf7e9e623549b0e21f6e97cf8ecf247c1a8fd2e8a992ae265314300b2455d5c"
+dependencies = [
+ "rand_core 0.3.1",
+]
+
+[[package]]
+name = "rdrand"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "678054eb77286b51581ba43620cc911abf02758c91f93f479767aed0f90458b2"
+dependencies = [
+ "rand_core 0.3.1",
 ]
 
 [[package]]
@@ -677,6 +1113,15 @@ version = "0.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d813022b2e00774a48eaf43caaa3c20b45f040ba8cbf398e2e8911a06668dbe6"
 
+[[package]]
+name = "remove_dir_all"
+version = "0.5.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4a83fa3702a688b9359eccba92d153ac33fd2e8462f9e0e3fdf155239ea7792e"
+dependencies = [
+ "winapi 0.3.8",
+]
+
 [[package]]
 name = "ring"
 version = "0.16.13"
@@ -703,6 +1148,15 @@ dependencies = [
  "opaque-debug",
 ]
 
+[[package]]
+name = "roxmltree"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d5001f134077069d87f77c8b9452b690df2445f7a43f1c7ca4a1af8dd505789d"
+dependencies = [
+ "xmlparser",
+]
+
 [[package]]
 name = "rug"
 version = "1.8.0"
@@ -720,7 +1174,7 @@ version = "0.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2bc8af4bda8e1ff4932523b94d3dd20ee30a87232323eda55903ffd71d2fb017"
 dependencies = [
- "base64",
+ "base64 0.11.0",
  "blake2b_simd",
  "constant_time_eq",
  "crossbeam-utils",
@@ -760,6 +1214,16 @@ version = "1.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ed3d612bc64430efeb3f7ee6ef26d590dce0c43249217bddc62112540c7941e1"
 
+[[package]]
+name = "schannel"
+version = "0.1.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8f05ba609c234e60bee0d547fe94a4c7e9da733d1c962cf6e59efa4cd9c8bc75"
+dependencies = [
+ "lazy_static",
+ "winapi 0.3.8",
+]
+
 [[package]]
 name = "scopeguard"
 version = "1.1.0"
@@ -768,9 +1232,11 @@ checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
 
 [[package]]
 name = "scryer-prolog"
-version = "0.8.123"
+version = "0.8.126"
 dependencies = [
+ "base64 0.12.3",
  "blake2",
+ "chrono",
  "cpu-time",
  "crossterm",
  "dirs",
@@ -781,19 +1247,57 @@ dependencies = [
  "indexmap",
  "lazy_static",
  "libc",
+ "native-tls",
  "nix 0.15.0",
  "num-rug-adapter",
+ "openssl",
  "ordered-float",
  "prolog_parser",
  "ref_thread_local",
  "ring",
  "ripemd160",
+ "roxmltree",
  "rug",
  "rustyline",
+ "select",
  "sha3",
+ "sodiumoxide",
  "unicode_reader",
 ]
 
+[[package]]
+name = "security-framework"
+version = "0.4.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "64808902d7d99f78eaddd2b4e2509713babc3dc3c85ad6f4c447680f3c01e535"
+dependencies = [
+ "bitflags",
+ "core-foundation",
+ "core-foundation-sys",
+ "libc",
+ "security-framework-sys",
+]
+
+[[package]]
+name = "security-framework-sys"
+version = "0.4.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "17bf11d99252f512695eb468de5516e5cf75455521e69dfe343f3b74e4748405"
+dependencies = [
+ "core-foundation-sys",
+ "libc",
+]
+
+[[package]]
+name = "select"
+version = "0.4.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ac645958c62108d11f90f8d34e4dc2799c838fc995ed4c2075867a2a8d5be76b"
+dependencies = [
+ "bit-set",
+ "html5ever",
+]
+
 [[package]]
 name = "semver"
 version = "0.9.0"
@@ -809,6 +1313,34 @@ version = "0.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "388a1df253eca08550bef6c72392cfe7c30914bf41df5269b68cbd6ff8f570a3"
 
+[[package]]
+name = "serde"
+version = "1.0.114"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5317f7588f0a5078ee60ef675ef96735a1442132dc645eb1d12c018620ed8cd3"
+
+[[package]]
+name = "serde_derive"
+version = "1.0.113"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "93c5eaa17d0954cb481cdcfffe9d84fcfa7a1a9f2349271e678677be4c26ae31"
+dependencies = [
+ "proc-macro2 1.0.10",
+ "quote 1.0.3",
+ "syn 1.0.18",
+]
+
+[[package]]
+name = "serde_json"
+version = "1.0.55"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ec2c5d7e739bc07a3e73381a39d61fdb5f671c60c1df26a130690665803d8226"
+dependencies = [
+ "itoa",
+ "ryu",
+ "serde",
+]
+
 [[package]]
 name = "sha3"
 version = "0.8.2"
@@ -843,6 +1375,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "siphasher"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0b8de496cf83d4ed58b6be86c3a275b8602f6ffe98d3024a869e124147a9a3ac"
+
 [[package]]
 name = "slab"
 version = "0.4.2"
@@ -864,6 +1402,17 @@ version = "1.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c7cb5678e1615754284ec264d9bb5b4c27d2018577fd90ac0ceb578591ed5ee4"
 
+[[package]]
+name = "sodiumoxide"
+version = "0.2.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7038b67c941e23501573cb7242ffb08709abe9b11eb74bceff875bbda024a6a8"
+dependencies = [
+ "libc",
+ "libsodium-sys",
+ "serde",
+]
+
 [[package]]
 name = "spin"
 version = "0.5.2"
@@ -876,21 +1425,101 @@ version = "0.3.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7f3eb36b47e512f8f1c9e3d10c2c1965bc992bd9cdb024fa581e2194501c83d3"
 
+[[package]]
+name = "string_cache"
+version = "0.7.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "89c058a82f9fd69b1becf8c274f412281038877c553182f1d02eb027045a2d67"
+dependencies = [
+ "lazy_static",
+ "new_debug_unreachable",
+ "phf_shared",
+ "precomputed-hash",
+ "serde",
+ "string_cache_codegen",
+ "string_cache_shared",
+]
+
+[[package]]
+name = "string_cache_codegen"
+version = "0.4.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f0f45ed1b65bf9a4bf2f7b7dc59212d1926e9eaf00fa998988e420fd124467c6"
+dependencies = [
+ "phf_generator",
+ "phf_shared",
+ "proc-macro2 1.0.10",
+ "quote 1.0.3",
+ "string_cache_shared",
+]
+
+[[package]]
+name = "string_cache_shared"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b1884d1bc09741d466d9b14e6d37ac89d6909cbcac41dd9ae982d4d063bbedfc"
+
 [[package]]
 name = "subtle"
 version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2d67a5a62ba6e01cb2192ff309324cb4875d0c451d55fe2319433abe7a05a8ee"
 
+[[package]]
+name = "syn"
+version = "0.15.44"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9ca4b3b69a77cbe1ffc9e198781b7acb0c7365a883670e8f1c1bc66fba79a5c5"
+dependencies = [
+ "proc-macro2 0.4.30",
+ "quote 0.6.13",
+ "unicode-xid 0.1.0",
+]
+
 [[package]]
 name = "syn"
 version = "1.0.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "410a7488c0a728c7ceb4ad59b9567eb4053d02e8cc7f5c0e0eeeb39518369213"
 dependencies = [
- "proc-macro2",
- "quote",
- "unicode-xid",
+ "proc-macro2 1.0.10",
+ "quote 1.0.3",
+ "unicode-xid 0.2.0",
+]
+
+[[package]]
+name = "tempfile"
+version = "3.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7a6e24d9338a0a5be79593e2fa15a648add6138caa803e2d5bc782c371732ca9"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "rand 0.7.3",
+ "redox_syscall",
+ "remove_dir_all",
+ "winapi 0.3.8",
+]
+
+[[package]]
+name = "tendril"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "707feda9f2582d5d680d733e38755547a3e8fb471e7ba11452ecfd9ce93a5d3b"
+dependencies = [
+ "futf",
+ "mac",
+ "utf-8",
+]
+
+[[package]]
+name = "time"
+version = "0.1.43"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ca8a50ef2360fbd1eeb0ecd46795a87a19024eb4b53c5dc916ca1fd95fe62438"
+dependencies = [
+ "libc",
+ "winapi 0.3.8",
 ]
 
 [[package]]
@@ -911,6 +1540,12 @@ version = "0.1.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "caaa9d531767d1ff2150b9332433f32a24622147e5ebb1f26409d5da67afd479"
 
+[[package]]
+name = "unicode-xid"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fc72304796d0818e357ead4e000d19c9c174ab23dc11093ac919054d20a6a7fc"
+
 [[package]]
 name = "unicode-xid"
 version = "0.2.0"
@@ -942,12 +1577,24 @@ version = "0.7.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a156c684c91ea7d62626509bce3cb4e1d9ed5c4d978f7b4352658f96a4c26b4a"
 
+[[package]]
+name = "utf-8"
+version = "0.7.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "05e42f7c18b8f902290b009cde6d651262f956c98bc51bca4cd1d511c9cd85c7"
+
 [[package]]
 name = "utf8parse"
 version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "936e4b492acfd135421d8dca4b1aa80a7bfc26e702ef3af710e0752684df5372"
 
+[[package]]
+name = "vcpkg"
+version = "0.2.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "55d1e41d56121e07f1e223db0a4def204e45c85425f6a16d462fd07c8d10d74c"
+
 [[package]]
 name = "void"
 version = "1.0.2"
@@ -979,9 +1626,9 @@ dependencies = [
  "bumpalo",
  "lazy_static",
  "log",
- "proc-macro2",
- "quote",
- "syn",
+ "proc-macro2 1.0.10",
+ "quote 1.0.3",
+ "syn 1.0.18",
  "wasm-bindgen-shared",
 ]
 
@@ -991,7 +1638,7 @@ version = "0.2.62"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2cd85aa2c579e8892442954685f0d801f9129de24fa2136b2c6a539c76b65776"
 dependencies = [
- "quote",
+ "quote 1.0.3",
  "wasm-bindgen-macro-support",
 ]
 
@@ -1001,9 +1648,9 @@ version = "0.2.62"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8eb197bd3a47553334907ffd2f16507b4f4f01bbec3ac921a7719e0decdfe72a"
 dependencies = [
- "proc-macro2",
- "quote",
- "syn",
+ "proc-macro2 1.0.10",
+ "quote 1.0.3",
+ "syn 1.0.18",
  "wasm-bindgen-backend",
  "wasm-bindgen-shared",
 ]
@@ -1067,3 +1714,9 @@ dependencies = [
  "winapi 0.2.8",
  "winapi-build",
 ]
+
+[[package]]
+name = "xmlparser"
+version = "0.13.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "52613e655f6f11f63c0fe7d1c3b5ef69e44d96df9b65dab296b441ed0e1125f5"

Cargo.toml

@@ -1,13 +1,13 @@
 [package]
 name = "scryer-prolog"
-version = "0.8.123"
+version = "0.8.127"
 authors = ["Mark Thom <markjordanthom@gmail.com>"]
 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-implementation"]
+keywords = ["prolog", "prolog-interpreter", "prolog-system"]
 categories = ["command-line-utilities"]
 build = "build.rs"
 
@@ -32,7 +32,7 @@ libc = "0.2.62"
 nix = "0.15.0"
 num-rug-adapter = { optional = true, version = "0.1.3" }
 ordered-float = "0.5.0"
-prolog_parser = { version = "0.8.59", default-features = false }
+prolog_parser = { version = "0.8.65", default-features = false }
 ref_thread_local = "0.0.0"
 rug = { version = "1.4.0", optional = true }
 rustyline = "6.0.0"
@@ -41,3 +41,10 @@ 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"

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
@@ -269,8 +271,13 @@ 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)` are ideally
-suited for reasoning about strings.
+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)
 
@@ -287,7 +294,7 @@ 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/prolog/lib/tabling.pl) and add a `(table)/1`
+[`library(tabling)`](src/lib/tabling.pl) and add a `(table)/1`
 directive for the desired predicate indicator. For example, if we
 write:
 
@@ -312,14 +319,14 @@ 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/prolog/lib/dif.pl),
-[`freeze/2`](src/prolog/lib/freeze.pl),
-[CLP(B)](src/prolog/lib/clpb.pl) and [CLP(ℤ)](src/prolog/lib/clpz.pl),
+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/prolog/lib/atts.pl) as in SICStus&nbsp;Prolog,
+[`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/prolog/lib/iso_ext.pl),
+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.
@@ -332,7 +339,7 @@ learning and developing portable CLP&nbsp;applications.
 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`](src/prolog/lib) for
+[`src/lib/*.pl`](src/lib) for
 examples.
 
 At the time of this writing, many predicates reside in their own
@@ -340,31 +347,31 @@ 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/prolog/lib/lists.pl)
+* [`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/prolog/lib/dcgs.pl)
+* [`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/prolog/lib/dif.pl)
+* [`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/prolog/lib/reif.pl)
+* [`reif`](src/lib/reif.pl)
   providing `if_/3`, `tfilter/3` and related predicates
   as described in *Indexing&nbsp;dif/2*.
-* [`clpz`](src/prolog/lib/clpz.pl)
+* [`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/prolog/lib/pairs.pl)
+* [`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/prolog/lib/si.pl)
+* [`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.
@@ -373,51 +380,84 @@ The modules that ship with Scryer&nbsp;Prolog are also called
   write `integer_si(X)` to ensure soundness of your programs.
   "si" stands for *sufficiently instantiated*, and also for
   *sound&nbsp;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)
+* [`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/prolog/lib/format.pl)
+* [`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` and `listing/1`
+  The predicates `format/[2,3]`, `portray_clause/[1,2]` and `listing/1`
   provide formatted *impure* output.
-* [`assoc`](src/prolog/lib/assoc.pl)
+* [`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/prolog/lib/ordsets.pl)
+* [`ordsets`](src/lib/ordsets.pl)
   represents ordered sets as lists.
-* [`clpb`](src/prolog/lib/clpb.pl)
+* [`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/prolog/lib/arithmetic.pl)
+* [`arithmetic`](src/lib/arithmetic.pl)
   Arithmetic predicates such as `lsb/2`, `msb/2` and
   `number_to_rational/2`.
-* [`time`](src/prolog/lib/time.pl)
-  `time/1` reports the CPU&nbsp;time of a goal. It is useful
-  for measuring the performance of your code.
-* [`cont`](src/prolog/lib/cont.pl)
+* [`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/prolog/lib/random.pl)
+* [`random`](src/lib/random.pl)
   Probabilistic predicates and random number generators.
-* [`sockets`](src/prolog/lib/sockets.pl)
+* [`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.
-* [`crypto`](src/prolog/lib/crypto.pl)
-  Cryptographically secure random numbers and hashes, HMAC-based
-  key derivation (HKDF), password-based key derivation (PBKDF2),
-  public key signatures and signature verification with Ed25519,
-  authenticated encryption, and reasoning about elliptic curves.
-
-To read contents of external files, use `phrase_from_file/2` from
-[`library(pio)`](src/prolog/lib/pio.pl) to apply a&nbsp;DCG to
-file&nbsp;contents. The predicates in
-[`library(charsio)`](src/prolog/lib/charsio.pl) are also useful for
-parsing.
+  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:
 
@@ -462,3 +502,17 @@ 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.
+
+### 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

@@ -1,60 +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    };
-}\n").unwrap();
-
-    libraries.write_all(b"\npub static PROJECT_DIR: &'static str = \"").unwrap();
-    libraries.write_all(env::var("CARGO_MANIFEST_DIR").unwrap().as_bytes()).unwrap();
-    libraries.write_all(b"\";\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="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

@@ -1,18 +1,18 @@
-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::heap::*;
-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};

src/clause_types.rs

@@ -1,10 +1,10 @@
-use prolog_parser::ast::*;
+use crate::prolog_parser::ast::*;
 
-use crate::prolog::forms::Number;
-use crate::prolog::machine::machine_indices::*;
-use crate::prolog::rug::rand::RandState;
+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;
 
@@ -171,6 +171,16 @@ pub enum SystemClauseType {
     CurrentHostname,
     CurrentInput,
     CurrentOutput,
+    DirectoryFiles,
+    FileSize,
+    FileExists,
+    DirectoryExists,
+    DirectorySeparator,
+    MakeDirectory,
+    DeleteFile,
+    WorkingDirectory,
+    PathCanonical,
+    FileTime,
     DeleteAttribute,
     DeleteHeadAttribute,
     DynamicModuleResolution(usize),
@@ -180,11 +190,11 @@ pub enum SystemClauseType {
     ExpandTerm,
     FetchGlobalVar,
     FetchGlobalVarWithOffset,
-    FileToChars,
     FirstStream,
     FlushOutput,
     GetByte,
     GetChar,
+    GetNChars,
     GetCode,
     GetSingleChar,
     ResetAttrVarState,
@@ -229,8 +239,8 @@ pub enum SystemClauseType {
     PeekCode,
     PointsToContinuationResetMarker,
     PutByte,
-    PutBytes,
     PutChar,
+    PutChars,
     PutCode,
     REPL(REPLCodePtr),
     ReadQueryTerm,
@@ -261,6 +271,7 @@ pub enum SystemClauseType {
     InstallNewBlock,
     Maybe,
     CpuNow,
+    CurrentTime,
     QuotedToken,
     ReadTermFromChars,
     ResetBlock,
@@ -293,10 +304,18 @@ pub enum SystemClauseType {
     CryptoPasswordHash,
     CryptoDataEncrypt,
     CryptoDataDecrypt,
+    CryptoCurveScalarMult,
     Ed25519Sign,
     Ed25519Verify,
     Ed25519NewKeyPair,
-    Ed25519KeyPairPublicKey
+    Ed25519KeyPairPublicKey,
+    Curve25519ScalarMult,
+    LoadHTML,
+    LoadXML,
+    GetEnv,
+    SetEnv,
+    UnsetEnv,
+    CharsBase64,
 }
 
 impl SystemClauseType {
@@ -324,6 +343,16 @@ impl SystemClauseType {
             &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::UseModule) => clause_name!("$use_module"),
             &SystemClauseType::REPL(REPLCodePtr::UseQualifiedModule) => {
@@ -348,11 +377,11 @@ impl SystemClauseType {
             &SystemClauseType::FetchGlobalVarWithOffset => {
                 clause_name!("$fetch_global_var_with_offset")
             }
-            &SystemClauseType::FileToChars => clause_name!("$file_to_chars"),
             &SystemClauseType::FirstStream => clause_name!("$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!("$reset_attr_var_state"),
@@ -397,6 +426,7 @@ impl SystemClauseType {
             &SystemClauseType::LiftedHeapLength => clause_name!("$lh_length"),
             &SystemClauseType::Maybe => clause_name!("maybe"),
             &SystemClauseType::CpuNow => clause_name!("$cpu_now"),
+            &SystemClauseType::CurrentTime => clause_name!("$current_time"),
             &SystemClauseType::ModuleAssertDynamicPredicateToFront => {
                 clause_name!("$module_asserta")
             }
@@ -416,12 +446,12 @@ impl SystemClauseType {
             &SystemClauseType::PutByte => {
                 clause_name!("$put_byte")
             }
-            &SystemClauseType::PutBytes => {
-                clause_name!("$put_bytes")
-            }
             &SystemClauseType::PutChar => {
                 clause_name!("$put_char")
             }
+            &SystemClauseType::PutChars => {
+                clause_name!("$put_chars")
+            }
             &SystemClauseType::PutCode => {
                 clause_name!("$put_code")
             }
@@ -488,10 +518,18 @@ impl SystemClauseType {
             &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::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"),
         }
     }
 
@@ -545,9 +583,9 @@ impl SystemClauseType {
             ("$expand_goal", 2) => Some(SystemClauseType::ExpandGoal),
             ("$fetch_global_var", 2) => Some(SystemClauseType::FetchGlobalVar),
             ("$fetch_global_var_with_offset", 3) => Some(SystemClauseType::FetchGlobalVarWithOffset),
-            ("$file_to_chars", 3) => Some(SystemClauseType::FileToChars),
             ("$get_byte", 2) => Some(SystemClauseType::GetByte),
             ("$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) => {
@@ -556,12 +594,12 @@ impl SystemClauseType {
             ("$put_byte", 2) => {
                 Some(SystemClauseType::PutByte)
             }
-            ("$put_bytes", 2) => {
-                Some(SystemClauseType::PutBytes)
-            }
             ("$put_char", 2) => {
                 Some(SystemClauseType::PutChar)
             }
+            ("$put_chars", 2) => {
+                Some(SystemClauseType::PutChars)
+            }
             ("$put_code", 2) => {
                 Some(SystemClauseType::PutCode)
             }
@@ -580,13 +618,14 @@ impl SystemClauseType {
             ("$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),
@@ -633,7 +672,7 @@ impl SystemClauseType {
             ("$set_seed", 1) => Some(SystemClauseType::SetSeed),
             ("$skip_max_list", 4) => Some(SystemClauseType::SkipMaxList),
             ("$sleep", 1) => Some(SystemClauseType::Sleep),
-            ("$socket_client_open", 7) => Some(SystemClauseType::SocketClientOpen),
+            ("$socket_client_open", 8) => Some(SystemClauseType::SocketClientOpen),
             ("$socket_server_open", 3) => Some(SystemClauseType::SocketServerOpen),
             ("$socket_server_accept", 7) => Some(SystemClauseType::SocketServerAccept),
             ("$socket_server_close", 1) => Some(SystemClauseType::SocketServerClose),
@@ -645,6 +684,16 @@ impl SystemClauseType {
             ("$unwind_environments", 0) => Some(SystemClauseType::UnwindEnvironments),
             ("$unwind_stack", 0) => Some(SystemClauseType::UnwindStack),
             ("$unify_with_occurs_check", 2) => Some(SystemClauseType::UnifyWithOccursCheck),
+            ("$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)),
             ("$use_module_from_file", 1) =>
                     Some(SystemClauseType::REPL(REPLCodePtr::UseModuleFromFile)),
@@ -658,15 +707,23 @@ impl SystemClauseType {
             ("$write_term_to_chars", 7) => Some(SystemClauseType::WriteTermToChars),
             ("$scryer_prolog_version", 1) => Some(SystemClauseType::ScryerPrologVersion),
             ("$crypto_random_byte", 1) => Some(SystemClauseType::CryptoRandomByte),
-            ("$crypto_data_hash", 3) => Some(SystemClauseType::CryptoDataHash),
-            ("$crypto_data_hkdf", 6) => Some(SystemClauseType::CryptoDataHKDF),
+            ("$crypto_data_hash", 4) => Some(SystemClauseType::CryptoDataHash),
+            ("$crypto_data_hkdf", 7) => Some(SystemClauseType::CryptoDataHKDF),
             ("$crypto_password_hash", 4) => Some(SystemClauseType::CryptoPasswordHash),
-            ("$crypto_data_encrypt", 5) => Some(SystemClauseType::CryptoDataEncrypt),
-            ("$crypto_data_decrypt", 5) => Some(SystemClauseType::CryptoDataDecrypt),
-            ("$ed25519_sign", 3) => Some(SystemClauseType::Ed25519Sign),
-            ("$ed25519_verify", 3) => Some(SystemClauseType::Ed25519Verify),
+            ("$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", 2) => Some(SystemClauseType::Ed25519KeyPairPublicKey),
+            ("$ed25519_keypair_public_key", 3) => Some(SystemClauseType::Ed25519KeyPairPublicKey),
+            ("$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,
         }
     }

src/codegen.rs

@@ -1,17 +1,17 @@
-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, IndexSet};
+use crate::indexmap::{IndexMap, IndexSet};
 
 use std::cell::Cell;
 use std::rc::Rc;

src/debray_allocator.rs

@@ -1,12 +1,12 @@
-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;

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/bimetatrans/bimetatrans.pl

@@ -1,4 +1,4 @@
-:- module(bimetatrans_ruleml, [parse_ruleml/3]).
+:- module(bimetatrans, [parse_ruleml/3]).
 
 :- use_module(library(dcgs)).
 :- use_module(library(iso_ext)).
@@ -19,28 +19,34 @@
  * all indentation stripped out. "Indented XML" contains indentation
  * and newlines, and is usually formatted for human readers.
  *
- * parse_ruleml/3 is the sole public predicate of BiMetaTrans(RuleML,
- * Prolog), a bidirectional translator capable of parsing well-formed
+ * parse_ruleml/3 is the sole public predicate of BiMetaTrans(Prolog,
+ * RuleML), a bidirectional translator capable of parsing well-formed
  * RuleML/XML (valid w.r.t. a proposed anchor schema nafhornlogeq
  * defining a sublanguage of the existing anchor schema naffologeq) to
  * an equivalent Prolog/'$V' term and back to RuleML/xmL. It has the
  * modes
  *
- * +AssertItem, +QueryItems, ?XML    (Prolog->RuleML)
- * ?AssertItem, ?QueryItems, +XML    (RuleML->Prolog)
+ * +AssertItems, +QueryItems, ?XML    (Prolog->RuleML)
+ * ?AssertItems, ?QueryItems, +XML    (RuleML->Prolog)
  *
  * The modes constrain the inputs to fit one of two patterns, the
- * first where AssertItem and QueryItem are instantiated and XML is
+ * 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.
  *
+ * A RuleML/XML document is assumed to contain an optional Assert
+ * element (with zero or more children) and zero or more Query
+ * elements. The children of the Assert element are the Items of
+ * AssertItems, while the Items of QueryItems each correspond to a
+ * single Query element.
+ *
  * parse_ruleml/3 is meant to subsume an invertible function in the
  * sense that the top-level query
  *
- * ?- parse_ruleml(AssertItem, QueryItems, XML0),    % Prolog->RuleML
- *    parse_ruleml(AssertItem0, QueryItems0, XML),   % RuleML->Prolog
- *    AssertItem0 == AssertItem,                     % Test for expected round-trip results.
+ * ?- parse_ruleml(AssertItems, QueryItems, XML0),    % Prolog->RuleML
+ *    parse_ruleml(AssertItems0, QueryItems0, XML),   % RuleML->Prolog
+ *    AssertItems0 == AssertItems,                    % Test for expected round-trip results.
  *    QueryItems0 == QueryItems,
  *    XML0 == XML.
  *
@@ -48,10 +54,11 @@
  * not 0-appended are instantiated and therefore ground.
  */
 
-parse_ruleml(AssertItem, QueryItem, XML) :-
-    (  ( var(AssertItem) ; var(QueryItem) ), var(XML) ->
+parse_ruleml(AssertItems, QueryItems, XML) :-
+    (  ( var(AssertItems) ; var(QueryItems) ), var(XML) ->
        throw(error(instantiation_error, parse_ruleml/2))
-    ;  phrase(ruleml_top_level_items(AssertItem, QueryItem), XML)
+    ;  phrase(ruleml_top_level_items(AssertItems, QueryItems), XML),
+       !
     ).
 
 
@@ -82,24 +89,15 @@ parse_header -->
  *
  * The two arguments are (un)instantiated depending on the direction
  * in which parse_ruleml/2 operates. In either direction, once
- * ruleml_query_item(QueryItems) or ruleml_assert(AssertItem)
- * succeeds:
- *
- * 1) AssertItem/QueryItems is a fully ground list of terms,
- * corresponding to an Assert/Query performative of the RuleML/XML KB.
- *
- * 2) It would not be meaningful to backtrack after the last success,
- * thus undoing its effects; that is because we have already refuted
- * the possibility of there being further items for the grammar to
- * consume. Hence we see that the cut (!) does not restrict the
- * generality of the grammar.
+ * ruleml_query_item(QueryItems) or ruleml_assert(AssertItems)
+ * succeeds, AssertItems and QueryItems are ground lists of terms,
+ * corresponding to Assert/Query performative(s) of the RuleML/XML KB.
  */
 
-ruleml_top_level_items(AssertItem, QueryItems) -->
-    (  ruleml_assert(AssertItem),
-       ruleml_query_items(QueryItems),
-       !
-    ;  { AssertItem = [] },
+ruleml_top_level_items(AssertItems, QueryItems) -->
+    (  ruleml_assert(AssertItems),
+       ruleml_query_items(QueryItems)
+    ;  { AssertItems = [] },
        ruleml_query_items(QueryItems)
     ).
 
@@ -169,22 +167,16 @@ ruleml_top_level_items(AssertItem, QueryItems) -->
  * outset of ruleml_assert//1 will cause it to fail, meaning that
  * an empty <Assert></Assert> element is never emitted to the output
  * RuleML/xmL.
- *
- * The two cuts are green cuts, meaning they do not change the meaning
- * or output of the program, they simply prevent needless
- * backtracking.
  */
 
 ruleml_assert(Items) -->
     (  { var(Items) } ->
        list_ws("<Assert mapClosure=\"universal\">"),
        ruleml_assert_items(Items),
-       !,
        list_ws("</Assert>")
     ;  "<Assert mapClosure=\"universal\">",
        { Items \== [] },
        ruleml_assert_items(Items),
-       !,
        "</Assert>"
     ).
 
@@ -206,7 +198,6 @@ ruleml_assert(Items) -->
 
 ruleml_assert_items([Item | Items]) -->
     ruleml_assert_item(Item),
-    !,
     ruleml_assert_items(Items).
 ruleml_assert_items([]) --> [].
 
@@ -214,7 +205,6 @@ ruleml_assert_items([]) --> [].
 ruleml_query_items(Items) -->
     (  { var(Items) } ->
        ruleml_query_item(Item),
-       !,
        (  { var(Item) } ->
           ruleml_query_items(Items)
        ;  { Items = [Item | Items0] },
@@ -222,7 +212,6 @@ ruleml_query_items(Items) -->
        )
     ;  { Items = [Item | Items0] },
        ruleml_query_item(Item),
-       !,
        ruleml_query_items(Items0)
     ).
 ruleml_query_items([]) --> [].
@@ -279,7 +268,7 @@ space(' ') --> " ".
 
 decimal_point('.') --> ".".
 
-sign('-') --> "-", !.
+sign('-') --> "-".
 sign('+') --> "+".
 
 double_quote('"') --> "\"".
@@ -332,7 +321,6 @@ ruleml_condition(Item) -->
 
 ruleml_item_conjunction([Item | Items]) -->
     ruleml_condition(Item),
-    !,
     ruleml_item_conjunction(Items).
 ruleml_item_conjunction([]) --> [].
 
@@ -404,7 +392,6 @@ ruleml_conjunction_of_items(Items) -->
 
 ruleml_item_disjunction([Item | Items]) -->
     ruleml_condition(Item),
-    !,
     ruleml_item_disjunction(Items).
 ruleml_item_disjunction([]) --> [].
 
@@ -549,7 +536,6 @@ ruleml_naf(Item) -->
 
 ruleml_atoms([Item|Items]) -->
     ruleml_atom(Item),
-    !,
     ruleml_atoms(Items).
 ruleml_atoms([]) --> [].
 
@@ -652,7 +638,6 @@ ruleml_expr(Item) -->
        (  list_ws("<repo>"),
           ruleml_item(RepoItem),
           list_ws("</repo>"),
-          !,
           { fold_commas(Args, ArgsCommas) },
           { Item =.. [Name, (ArgsCommas | RepoItem)] }
        ;  { Item =.. [Name | Args] }
@@ -823,15 +808,12 @@ ruleml_data(Name) -->
  * converting from lists of characters (here denoted as Cs) to the
  * named data type in ISO Prolog. The type information is given
  * in the first argument.
- *
- * Grammatically, ruleml_data_contents//3 is a disjoint union of its
- * subgrammars, justifying the cut at the end of the first two rules.
  */
 
 ruleml_data_contents(number, Cs) -->
-    ruleml_number(Cs), !.
+    ruleml_number(Cs).
 ruleml_data_contents(symbol, Cs) -->
-    ruleml_symbol(Cs), !.
+    ruleml_symbol(Cs).
 ruleml_data_contents(string, Cs) -->
     ruleml_string(Cs).
 
@@ -1195,8 +1177,7 @@ fold_semicolons(List, Output) :-
  * complicated by Scryer's current lack of multi-argument indexing.
  */
 
-fold_list([Item], _, Item) :-
-    !.
+fold_list([Item], _, Item).
 fold_list([Item|Items], F, Form) :-
     Form =.. [F, Item, Fs],
     fold_list(Items, F, Fs).

src/examples/least_time.pl

@@ -11,11 +11,12 @@
  */
 
 :- module(least_time, [find_min_time/2,
-		       write_time_nl/1]).
+		               write_time_nl/1]).
 
 
 :- use_module(library(dcgs)).
 :- use_module(library(format)).
+:- use_module(library(lists)).
 :- use_module(library(reif)).
 
 
@@ -32,10 +33,10 @@ valid_time([H1,H2,M1,M2], T) :-
     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
-	  )
+	      (  H2 =< 3 ->
+	         T = true
+	      ;  T = false
+	      )
        ;  T = true
        )
     ;  T = false
@@ -49,15 +50,7 @@ permuted_times(Time, PermutedTimes) :-
 
 find_min_time(Time, Min) :-
     valid_time(Time, true),
-    permuted_times(Time, PermutedTimes),
-    find_min_time_(PermutedTimes, Time, Min).
-
-find_min_time_([], Min, Min).
-find_min_time_([Time|Times], MinSoFar, Min) :-
-    (  Time @< MinSoFar ->
-       find_min_time_(Times, Time, Min)
-    ;  find_min_time_(Times, MinSoFar, Min)
-    ).
+    permuted_times(Time, [Min|_]).
 
 
 write_time_nl(Time) :-

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

@@ -1,10 +1,10 @@
-use prolog_parser::ast::*;
+use crate::prolog_parser::ast::*;
 
-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;

src/forms.rs

@@ -1,14 +1,14 @@
-use prolog_parser::ast::*;
-use prolog_parser::parser::OpDesc;
-use prolog_parser::tabled_rc::*;
+use crate::prolog_parser::ast::*;
+use crate::prolog_parser::parser::OpDesc;
+use crate::prolog_parser::tabled_rc::*;
 
-use crate::prolog::clause_types::*;
-use crate::prolog::machine::machine_errors::*;
-use crate::prolog::machine::machine_indices::*;
-use crate::prolog::ordered_float::OrderedFloat;
-use crate::prolog::rug::{Integer, Rational};
+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 indexmap::IndexMap;
+use crate::indexmap::IndexMap;
 
 use std::cell::Cell;
 use std::collections::VecDeque;
@@ -505,11 +505,11 @@ pub fn fetch_atom_op_spec(
     spec: Option<SharedOpDesc>,
     op_dir: &OpDir,
 ) -> Option<SharedOpDesc> {
-    fetch_op_spec(name.clone(), 1, spec.clone(), op_dir)
-        .or_else(|| fetch_op_spec(name, 2, spec, op_dir))
+    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(
+pub fn fetch_op_spec_from_existing(
     name: ClauseName,
     arity: usize,
     spec: Option<SharedOpDesc>,
@@ -524,7 +524,15 @@ pub fn fetch_op_spec(
         }
     }
 
-    spec.or_else(|| match arity {
+    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, _)| {
@@ -542,7 +550,7 @@ pub fn fetch_op_spec(
             }
 
             op_dir
-                .get(&(name.clone(), Fixity::Post))
+                .get(&(name, Fixity::Post))
                 .and_then(|OpDirValue(spec, _)| {
                     if spec.prec() > 0 {
                         Some(spec.clone())
@@ -551,8 +559,10 @@ pub fn fetch_op_spec(
                     }
                 })
         }
-        _ => None,
-    })
+        _ => {
+            None
+        }
+    }
 }
 
 pub type ModuleDir = IndexMap<ClauseName, Module>;

src/heap_iter.rs

@@ -1,7 +1,7 @@
-use crate::prolog::machine::machine_indices::*;
-use crate::prolog::machine::machine_state::*;
+use crate::machine::machine_indices::*;
+use crate::machine::machine_state::*;
 
-use indexmap::IndexSet;
+use crate::indexmap::IndexSet;
 
 use std::cmp::Ordering;
 use std::ops::Deref;
@@ -93,21 +93,19 @@ impl<'a> HCPreOrderIterator<'a> {
             }
             Addr::Con(h) => {
                 if let &HeapCellValue::PartialString(ref pstr, has_tail) = &self.machine_st.heap[h] {
-                    if !self.machine_st.flags.double_quotes.is_atom() {
-                        return 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));
+                    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
-                        };
+                        Addr::PStrLocation(h, 0)
+                    } else if has_tail {
+                        self.follow(Addr::HeapCell(h + 1))
+                    } else {
+                        Addr::EmptyList
                     }
+                } else {
+                    Addr::Con(h)
                 }
-
-                Addr::Con(h)
             }
             da => {
                 da

src/heap_print.rs

@@ -1,16 +1,16 @@
-use prolog_parser::ast::*;
+use crate::prolog_parser::ast::*;
 
-use crate::prolog::clause_types::*;
-use crate::prolog::forms::*;
-use crate::prolog::heap_iter::*;
-use crate::prolog::machine::heap::*;
-use crate::prolog::machine::machine_indices::*;
-use crate::prolog::machine::machine_state::*;
-use crate::prolog::machine::streams::*;
-use crate::prolog::ordered_float::OrderedFloat;
-use crate::prolog::rug::{Integer, Rational};
+use crate::clause_types::*;
+use crate::forms::*;
+use crate::heap_iter::*;
+use crate::machine::heap::*;
+use crate::machine::machine_indices::*;
+use crate::machine::machine_state::*;
+use crate::machine::streams::*;
+use crate::ordered_float::OrderedFloat;
+use crate::rug::{Integer, Rational};
 
-use indexmap::{IndexMap, IndexSet};
+use crate::indexmap::{IndexMap, IndexSet};
 
 use std::cell::Cell;
 use std::convert::TryFrom;
@@ -449,8 +449,6 @@ fn non_quoted_token<Iter: Iterator<Item = char>>(mut iter: Iter) -> bool {
     if let Some(c) = iter.next() {
         if small_letter_char!(c) {
             iter.all(|c| alpha_numeric_char!(c))
-        } else if c == '.' {
-            iter.next().is_some()
         } else if graphic_token_char!(c) {
             non_quoted_graphic_token(iter, c)
         } else if semicolon_char!(c) {
@@ -1173,7 +1171,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
         let at_cdr = self.at_cdr(",");
 
         if !at_cdr && Addr::EmptyList == end_addr {
-            if self.machine_st.flags.double_quotes.is_chars() && !self.ignore_ops {
+            if !self.ignore_ops {
                 self.print_proper_string(buf, max_depth);
                 return;
             }
@@ -1190,18 +1188,6 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
 
         let mut byte_len = 0;
 
-        let char_printer = |printer: &mut Self, c| {
-            if printer.machine_st.flags.double_quotes.is_codes() {
-                let s = (c as u32).to_string();
-
-                push_space_if_amb!(printer, &s, {
-                    printer.append_str(&s);
-                });
-            } else {
-                printer.print_char(printer.quoted, c);
-            }
-        };
-
         if self.ignore_ops {
             let mut char_count = 0;
 
@@ -1209,7 +1195,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
                 self.append_str("'.'");
                 self.push_char('(');
 
-                char_printer(self, c);
+                self.print_char(self.quoted, c);
                 self.push_char(',');
 
                 char_count += 1;
@@ -1235,7 +1221,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
             };
 
             for c in buf_iter {
-                char_printer(self, c);
+                self.print_char(self.quoted, c);
                 self.push_char(',');
 
                 byte_len += c.len_utf8();
@@ -1312,6 +1298,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
                     !iter.immediate_leaf_has_property(|addr, heap| {
                         match heap.index_addr(&addr).as_ref() {
                             &HeapCellValue::Integer(ref n) => &**n >= &0,
+                            &HeapCellValue::Addr(Addr::Fixnum(n)) => n >= 0,
                             &HeapCellValue::Addr(Addr::Float(f)) => f >= OrderedFloat(0f64),
                             &HeapCellValue::Rational(ref r) => &**r >= &0,
                             _ => false
@@ -1422,7 +1409,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
 
         match self.machine_st.heap.index_addr(&addr).as_ref() {
             &HeapCellValue::NamedStr(arity, ref name, ref spec) => {
-                let spec = fetch_op_spec(name.clone(), arity, spec.clone(), self.op_dir);
+                let spec = fetch_op_spec_from_existing(name.clone(), arity, spec.clone(), self.op_dir);
 
                 if let Some(spec) = spec {
                     self.handle_op_as_struct(

src/indexing.rs

@@ -1,10 +1,10 @@
-use prolog_parser::ast::*;
-use prolog_parser::tabled_rc::*;
+use crate::prolog_parser::ast::*;
+use crate::prolog_parser::tabled_rc::*;
 
-use crate::prolog::instructions::*;
-use crate::prolog::rug::Integer;
+use crate::instructions::*;
+use crate::rug::Integer;
 
-use indexmap::IndexMap;
+use crate::indexmap::IndexMap;
 
 use std::collections::VecDeque;
 use std::convert::TryFrom;
@@ -123,10 +123,6 @@ impl CodeOffsets {
                     code.push(Self::add_index(code.is_empty(), index));
                 }
             }
-            &Constant::String(_) => {
-                let is_initial_index = self.lists.is_empty();
-                self.lists.push(Self::add_index(is_initial_index, index));
-            }
             &Constant::Usize(n) => {
                 let code = self.constants
                     .entry(Constant::Integer(Rc::new(Integer::from(n))))
@@ -158,7 +154,7 @@ impl CodeOffsets {
                 let is_initial_index = code.is_empty();
                 code.push(Self::add_index(is_initial_index, index));
             }
-            &Term::Cons(..) => {
+            &Term::Cons(..) | &Term::Constant(_, Constant::String(_)) => {
                 let is_initial_index = self.lists.is_empty();
                 self.lists.push(Self::add_index(is_initial_index, index));
             }
@@ -172,7 +168,8 @@ impl CodeOffsets {
                 let is_initial_index = code.is_empty();
                 code.push(Self::add_index(is_initial_index, index));
             }
-            _ => {}
+            _ => {
+            }
         };
     }
 

src/instructions.rs

@@ -1,13 +1,13 @@
-use prolog_parser::ast::*;
+use crate::prolog_parser::ast::*;
 
-use crate::prolog::clause_types::*;
-use crate::prolog::forms::*;
-use crate::prolog::machine::heap::*;
-use crate::prolog::machine::machine_errors::MachineStub;
-use crate::prolog::machine::machine_indices::*;
-use crate::prolog::rug::Integer;
+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 indexmap::IndexMap;
+use crate::indexmap::IndexMap;
 
 use std::collections::VecDeque;
 use std::rc::Rc;

src/iterators.rs

@@ -1,8 +1,8 @@
-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;

src/lib/builtins.pl

@@ -24,6 +24,8 @@ user:term_expansion((:- op(Pred, Spec, [Op | OtherOps])), OpResults) :-
 :- op(400, yfx, [div, //, rdiv, <<, >>, mod, rem]).
 :- op(200, fy, [+, -, \]).
 
+:- op(1200, xfx, -->).
+
 % arithmetic comparison operators.
 :- op(700, xfx, [>, <, =\=, =:=, >=, =<]).
 
@@ -52,7 +54,7 @@ user:term_expansion((:- op(Pred, Spec, [Op | OtherOps])), OpResults) :-
                      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, max_arity/1, number_chars/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,
@@ -912,7 +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)

src/lib/charsio.pl

@@ -1,8 +1,10 @@
 :- 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]).
+                    write_term_to_chars/3,
+                    chars_base64/3]).
 
 :- use_module(library(dcgs)).
 :- use_module(library(iso_ext)).
@@ -140,7 +142,6 @@ write_term_to_chars(Term, Options, Chars) :-
     '$write_term_to_chars'(Chars, Term, IgnoreOps, NumberVars, Quoted, NewVarNames, MaxDepth).
 
 % Encodes Ch character to list of Bytes.
-% TODO: if Ch is variable, decode Bytes to Char.
 char_utf8bytes(Ch, Bytes) :-
   char_code(Ch, Code),
   phrase(code_to_utf8(Code), Bytes).
@@ -155,10 +156,87 @@ encode(Code, Prefix, Nb) -->
   { Nb1 is Nb - 1, Byte is Prefix \/ ((Code >> (6 * Nb1)) /\ 0x3F) },
   [Byte], encode(Code, 0x80, Nb1).
 
-% Encodes a list of characters Cs to a list of UTF-8 bytes Bs.
-% TODO: if Cs is variable, decode bytes to chars instead. 
+% 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) :-
-  must_be(list, Cs),
-  maplist(must_be(atom), Cs),
-  maplist(char_utf8bytes, Cs, Bss),
-  append(Bss, 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/crypto.pl

@@ -29,6 +29,8 @@
            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
@@ -43,6 +45,7 @@
 :- use_module(library(arithmetic)).
 :- use_module(library(format)).
 :- use_module(library(charsio)).
+:- use_module(library(si)).
 
 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    hex_bytes(?Hex, ?Bytes) is det.
@@ -76,13 +79,13 @@ hex_bytes([]) --> [].
 hex_bytes([H1,H2|Hs]) --> [Byte],
         { char_hexval(H1, High),
           char_hexval(H2, Low),
-          Byte is High*16 + Low },
+          Byte #= High*16 + Low },
         hex_bytes(Hs).
 
 bytes_hex([]) --> [].
 bytes_hex([B|Bs]) --> [C0,C1],
-        { High is B>>4,
-          Low is B /\ 0xf,
+        { High #= B>>4,
+          Low #= B /\ 0xf,
           char_hexval(C0, High),
           char_hexval(C1, Low)
         },
@@ -101,6 +104,16 @@ must_be_bytes(Bytes, Context) :-
         ).
 
 
+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
    =======================================
@@ -191,18 +204,18 @@ crypto_random_byte(B) :- '$crypto_random_byte'(B).
 
 crypto_data_hash(Data0, Hash, Options0) :-
         must_be(list, Options0),
-        options_data_bytes(Options0, Data0, Data),
+        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)
         ),
-        '$crypto_data_hash'(Data, HashBytes, A),
+        '$crypto_data_hash'(Data, Encoding, HashBytes, A),
         hex_bytes(Hash, HashBytes).
 
-options_data_bytes(Options, Data, Bytes) :-
+options_data_chars(Options, Data, Chars, Encoding) :-
         option(encoding(Encoding), Options, utf8),
         must_be(atom, Encoding),
-        encoding_bytes(Encoding, Data, Bytes).
+        encoding_chars(Encoding, Data, Chars).
 
 default_hash(sha256).
 
@@ -270,12 +283,12 @@ crypto_data_hkdf(Data0, L, Bytes, Options0) :-
         ),
         must_be(integer, L),
         L >= 0,
-        options_data_bytes(Options, Data0, Data),
+        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),
-        '$crypto_data_hkdf'(Data, SaltBytes, Info, Algorithm, L, Bytes).
+        '$crypto_data_hkdf'(Data, Encoding, SaltBytes, Info, Algorithm, L, Bytes).
 
 hkdf_algorithm(sha256).
 hkdf_algorithm(sha384).
@@ -416,61 +429,17 @@ crypto_password_hash(Password0, Hash, Options) :-
 
 
 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-   Bidirectional Bytes <-> Base64 conversion
-   =========================================
-
-   This implements Base64 conversion *without padding*.
+   Bidirectional Bytes <-> Base64 conversion *without padding*.
 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 
-n_base64(0 , 'A'). n_base64(1 , 'B'). n_base64(2 , 'C'). n_base64(3 , 'D').
-n_base64(4 , 'E'). n_base64(5 , 'F'). n_base64(6 , 'G'). n_base64(7 , 'H').
-n_base64(8 , 'I'). n_base64(9 , 'J'). n_base64(10, 'K'). n_base64(11, 'L').
-n_base64(12, 'M'). n_base64(13, 'N'). n_base64(14, 'O'). n_base64(15, 'P').
-n_base64(16, 'Q'). n_base64(17, 'R'). n_base64(18, 'S'). n_base64(19, 'T').
-n_base64(20, 'U'). n_base64(21, 'V'). n_base64(22, 'W'). n_base64(23, 'X').
-n_base64(24, 'Y'). n_base64(25, 'Z'). n_base64(26, 'a'). n_base64(27, 'b').
-n_base64(28, 'c'). n_base64(29, 'd'). n_base64(30, 'e'). n_base64(31, 'f').
-n_base64(32, 'g'). n_base64(33, 'h'). n_base64(34, 'i'). n_base64(35, 'j').
-n_base64(36, 'k'). n_base64(37, 'l'). n_base64(38, 'm'). n_base64(39, 'n').
-n_base64(40, 'o'). n_base64(41, 'p'). n_base64(42, 'q'). n_base64(43, 'r').
-n_base64(44, 's'). n_base64(45, 't'). n_base64(46, 'u'). n_base64(47, 'v').
-n_base64(48, 'w'). n_base64(49, 'x'). n_base64(50, 'y'). n_base64(51, 'z').
-n_base64(52, '0'). n_base64(53, '1'). n_base64(54, '2'). n_base64(55, '3').
-n_base64(56, '4'). n_base64(57, '5'). n_base64(58, '6'). n_base64(59, '7').
-n_base64(60, '8'). n_base64(61, '9'). n_base64(62, '+'). n_base64(63, '/').
-
-bytes_base64(Ls, Bs) :-
-        (   list(Bs), maplist(atom, Bs) ->
-            maplist(n_base64, Is, Bs),
-            phrase(bytes_base64_(Ls), Is),
-            Ls ins 0..255
-        ;   phrase(bytes_base64_(Ls), Is),
-            Is ins 0..63,
-            maplist(n_base64, Is, Bs)
+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)])
         ).
 
-list(Ls) :-
-        nonvar(Ls),
-        (   Ls = [] -> true
-        ;   Ls = [_|Rest],
-            list(Rest)
-        ).
-
-bytes_base64_([])         --> [].
-bytes_base64_([A])        --> [W,X],
-        { A #= W*4 + X//16,
-          X #= 16*_ }.
-bytes_base64_([A,B])      --> [W,X,Y],
-        { A #= W*4 + X//16,
-          B #= (X mod 16)*16 + Y//4,
-          Y #= 4*_ }.
-bytes_base64_([A,B,C|Ls]) --> [W,X,Y,Z],
-        { A #= W*4 + X//16,
-          B #= (X mod 16)*16 + Y//4,
-          C #= (Y mod 4)*64 + Z },
-        bytes_base64_(Ls).
-
-
 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    crypto_data_encrypt(+PlainText,
                        +Algorithm,
@@ -558,7 +527,7 @@ bytes_base64_([A,B,C|Ls]) --> [W,X,Y,Z],
 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 
 crypto_data_encrypt(PlainText0, Algorithm, Key, IV, CipherText, Options) :-
-        options_data_bytes(Options, PlainText0, PlainText),
+        options_data_chars(Options, PlainText0, PlainText, Encoding),
         option(tag(Tag), Options, _),
         (   nonvar(Tag) ->
             must_be_bytes(Tag, crypto_data_encrypt/6)
@@ -570,7 +539,7 @@ crypto_data_encrypt(PlainText0, Algorithm, Key, IV, CipherText, Options) :-
         (   Algorithm = 'chacha20-poly1305' -> true
         ;   domain_error('chacha20-poly1305', Algorithm, crypto_data_encrypt/6)
         ),
-        '$crypto_data_encrypt'(PlainText, Key, IV, Tag, CipherText).
+        '$crypto_data_encrypt'(PlainText, Encoding, Key, IV, Tag, CipherText).
 
 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   crypto_data_decrypt(+CipherText,
@@ -610,26 +579,25 @@ crypto_data_decrypt(CipherText0, Algorithm, Key, IV, PlainText, Options) :-
         must_be(atom, Encoding),
         member(Encoding, [utf8,octet]),
         must_be(list, CipherText0),
-        encoding_bytes(octet, CipherText0, CipherText1),
-        append(CipherText1, Tag, CipherText),
+        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)
         ),
-        '$crypto_data_decrypt'(CipherText, Key, IV, Encoding, PlainText).
+        '$crypto_data_decrypt'(CipherText, octet, Key, IV, Encoding, PlainText).
 
-encoding_bytes(octet, Bs0, Bs) :-
-        must_be(list, Bs0),
-        (   maplist(integer, Bs0) ->
-            Bs0 = Bs
-        ;   maplist(char_code, Bs0, Bs)
+
+encoding_chars(octet, Bs, Cs) :-
+        must_be(list, Bs),
+        (   maplist(integer, Bs) ->
+            maplist(char_code, Cs, Bs)
+        ;   Bs = Cs
         ),
-        must_be_bytes(Bs, crypto_encoding).
-encoding_bytes(utf8, Cs, Bs) :-
+        must_be_byte_chars(Cs, crypto_encoding).
+encoding_chars(utf8, Cs, Cs) :-
         must_be(list, Cs),
-        (   maplist(atom, Cs) ->
-            chars_bytes_(Cs, Bs, crypto_encoding)
-        ;   domain_error(encryption_encoding, Cs, crypto)
-        ).
+        maplist(must_be(character), Cs).
 
 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    Digital signatures with Ed25519
@@ -667,60 +635,77 @@ encoding_bytes(utf8, Cs, Bs) :-
 ed25519_new_keypair(Pair) :-
         '$ed25519_new_keypair'(Pair).
 
-ed25519_keypair_public_key(Pair0, PublicKey) :-
-        encoding_bytes(octet, Pair0, Pair),
-        '$ed25519_keypair_public_key'(Pair, PublicKey).
+ed25519_keypair_public_key(Pair, PublicKey) :-
+        must_be_byte_chars(Pair, ed25519_keypair_public_key),
+        '$ed25519_keypair_public_key'(Pair, octet, PublicKey).
 
-ed25519_sign(Key0, Data0, Signature, Options) :-
-        options_data_bytes(Options, Data0, Data),
-        encoding_bytes(octet, Key0, Key),
-        '$ed25519_sign'(Key, Data, Signature0),
+ed25519_sign(Key, Data0, Signature, Options) :-
+        must_be_byte_chars(Key, ed25519_sign),
+        options_data_chars(Options, Data0, Data, Encoding),
+        '$ed25519_sign'(Key, octet, Data, Encoding, Signature0),
         hex_bytes(Signature, Signature0).
 
-ed25519_verify(Key0, Data0, Signature0, Options) :-
-        options_data_bytes(Options, Data0, Data),
-        encoding_bytes(octet, Key0, Key),
+ed25519_verify(Key, Data0, Signature0, Options) :-
+        must_be_byte_chars(Key, ed25519_verify),
+        options_data_chars(Options, Data0, Data, Encoding),
         hex_bytes(Signature0, Signature),
-        '$ed25519_verify'(Key, Data, Signature).
+        '$ed25519_verify'(Key, octet, Data, Encoding, Signature).
 
 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-   Modular multiplicative inverse.
+   X25519: ECDH key exchange over Curve25519
+   =========================================
 
-   Compute Y = X^(-1) mod p, using the extended Euclidean algorithm.
+   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.
 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 
-multiplicative_inverse_modulo_p(X, P, Y) :-
-        eea(X, P, _, _, Y),
-        R #= X*Y mod P,
-        zcompare(C, 1, R),
-        must_be_one(C, X, P, Y).
+curve25519_generator(Gs) :-
+        length(Gs0, 32),
+        Gs0 = [9|Zs],
+        maplist(=(0), Zs),
+        maplist(char_code, Gs, Gs0).
 
-must_be_one(=, _, _, _).
-must_be_one(>, X, P, Y) :- throw(multiplicative_inverse_modulo_p(X,P,Y)).
-must_be_one(<, X, P, Y) :- throw(multiplicative_inverse_modulo_p(X,P,Y)).
+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).
 
-/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-   Extended Euclidean algorithm.
-
-   Computes the GCD and the Bézout coefficients S and T.
-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
-
-eea(I, J, G, S, T) :-
-        State0 = state(1,0,0,1),
-        eea_loop(I, J, State0, G, S, T).
-
-eea_loop(I, J, State0, G, S, T) :-
-        zcompare(C, 0, J),
-        eea_(C, I, J, State0, G, S, T).
-
-eea_(=, I, _, state(_,_,U,V), I, U, V).
-eea_(<, I0, J0, state(S0,T0,U0,V0), I, U, V) :-
-        Q #= I0 // J0,
-        R #= I0 mod J0,
-        S1 #= U0 - (Q*S0),
-        T1 #= V0 - (Q*T0),
-        eea_loop(J0, R, state(S1,T1,S0,T0), I, U, V).
+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
@@ -728,7 +713,7 @@ eea_(<, I0, J0, state(S0,T0,U0,V0), I, U, V) :-
 
    Sample use: Establishing a shared secret S, using ECDH key exchange.
 
-    ?- crypto_name_curve(Name, C),
+    ?- crypto_name_curve(secp256k1, C),
        crypto_curve_generator(C, Generator),
        PrivateKey = 10,
        crypto_curve_scalar_mult(C, PrivateKey, Generator, PublicKey),
@@ -737,95 +722,44 @@ eea_(<, I0, J0, state(S0,T0,U0,V0), I, U, V) :-
        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(P,A,B,point(X,Y),Order,Cofactor).
+   curve(Name,P,A,B,point(X,Y),Order,FieldLength,Cofactor).
 
    First, we define suitable accessors.
 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 
-curve_p(curve(P,_,_,_,_,_), P).
-curve_a(curve(_,A,_,_,_,_), A).
-curve_b(curve(_,_,B,_,_,_), B).
+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_order(curve(_,_,_,_,Order,_), Order).
-crypto_curve_generator(curve(_,_,_,G,_,_), G).
+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).
 
 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-   Scalar point multiplication.
-
-   R = k*Q.
-
-   The Montgomery ladder method is used to mitigate side-channel
-   attacks such as timing attacks, since the number of multiplications
-   and additions is independent of the private key K. This method does
-   not even reveal the key's Hamming weight (number of 1s).
+?- crypto_name_curve(secp256k1, Curve),
+   crypto_curve_generator(Curve, G),
+   crypto_curve_scalar_mult(Curve, 2, G, R).
 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 
-crypto_curve_scalar_mult(Curve, K, Q, R) :-
-        msb(K, Upper),
-        scalar_multiplication(Curve, K, Upper, ml(null,Q)-R),
-        must_be_on_curve(Curve, R).
-
-scalar_multiplication(Curve, K, I, R0-R) :-
-        zcompare(C, -1, I),
-        scalar_mult_(C, Curve, K, I, R0-R).
-
-scalar_mult_(=, _, _, _, ml(R,_)-R).
-scalar_mult_(<, Curve, K, I0, ML0-R) :-
-        BitSet #= K /\ (1 << I0),
-        zcompare(C, 0, BitSet),
-        montgomery_step(C, Curve, ML0, ML1),
-        I1 #= I0 - 1,
-        scalar_multiplication(Curve, K, I1, ML1-R).
-
-montgomery_step(=, Curve, ml(R0,S0), ml(R,S)) :-
-        curve_points_addition(Curve, R0, S0, S),
-        curve_point_double(Curve, R0, R).
-montgomery_step(<, Curve, ml(R0,S0), ml(R,S)) :-
-        curve_points_addition(Curve, R0, S0, R),
-        curve_point_double(Curve, S0, S).
-
-/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-   Doubling a point: R = A + A.
-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
-
-curve_point_double(_, null, null).
-curve_point_double(Curve, point(AX,AY), R) :-
-        curve_p(Curve, P),
-        curve_a(Curve, A),
-        Numerator #= (3*AX^2 + A) mod P,
-        Denom0 #= 2*AY mod P,
-        multiplicative_inverse_modulo_p(Denom0, P, Denom),
-        S #= (Numerator*Denom) mod P,
-        R = point(RX,RY),
-        RX #= (S^2 - 2*AX) mod P,
-        RY #= (S*(AX - RX) - AY) mod P,
-        must_be_on_curve(Curve, R).
-
-/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-   Adding two points.
-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
-
-curve_points_addition(Curve, P, Q, R) :-
-        curve_points_addition_(P, Curve, Q, R).
-
-curve_points_addition_(null, _, P, P).
-curve_points_addition_(P, _, null, P).
-curve_points_addition_(point(AX,AY), Curve, point(BX,BY), R) :-
-        curve_p(Curve, P),
-        Numerator #= (AY - BY) mod P,
-        Denom0 #= (AX - BX) mod P,
-        multiplicative_inverse_modulo_p(Denom0, P, Denom),
-        S #= (Numerator * Denom) mod P,
-        R = point(RX,RY),
-        RX #= (S^2 - AX - BX) mod P,
-        RY #= (S*(AX - RX) - AY) mod P,
-        must_be_on_curve(Curve, R).
-
 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    Validation.
 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
@@ -838,7 +772,7 @@ curve_contains_point(Curve, point(QX,QY)) :-
 
 must_be_on_curve(Curve, P) :-
         \+ curve_contains_point(Curve, P),
-        throw(not_on_curve(P)).
+        domain_error(point_on_curve, P, crypto_elliptic_curves).
 must_be_on_curve(Curve, P) :- curve_contains_point(Curve, P).
 
 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@@ -855,21 +789,38 @@ must_be_on_curve(Curve, P) :- curve_contains_point(Curve, P).
                      -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(0x00db7c2abf62e35e668076bead208b,
+                  curve(secp112r1,
+                        0x00db7c2abf62e35e668076bead208b,
                         0x00db7c2abf62e35e668076bead2088,
                         0x659ef8ba043916eede8911702b22,
                         point(0x09487239995a5ee76b55f9c2f098,
                               0xa89ce5af8724c0a23e0e0ff77500),
                         0x00db7c2abf62e35e7628dfac6561c5,
+                        14,
                         1)).
 crypto_name_curve(secp256k1,
-                  curve(0x00fffffffffffffffffffffffffffffffffffffffffffffffffffffffefffffc2f,
+                  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

@@ -1,7 +1,7 @@
-:- module(dcgs, [op(1200, xfx, -->),
-		 op(1105, xfy, '|'),
-		 phrase/2,
-		 phrase/3]).
+:- module(dcgs,
+          [op(1105, xfy, '|'),
+		   phrase/2,
+		   phrase/3]).
 
 :- use_module(library(error)).
 :- use_module(library(lists), [append/3]).

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/error.pl

@@ -27,7 +27,8 @@
 
        - integer
        - atom
-       - list.
+       - list
+       - boolean
 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 
 must_be(Type, Term) :-
@@ -43,8 +44,10 @@ must_be_(var, Term) :-
         ).
 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(must_be/2)
@@ -52,6 +55,12 @@ check_(Pred, Type, Term) :-
         ;   type_error(Type, Term, must_be/2)
         ).
 
+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).
@@ -59,8 +68,10 @@ ilist([_|Ls]) :- ilist(Ls).
 type(type).
 type(integer).
 type(atom).
+type(character).
 type(list).
 type(var).
+type(boolean).
 
 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    can_be(Type, Term)
@@ -85,7 +96,9 @@ can_be(Type, Term) :-
 
 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([]).

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

@@ -3,7 +3,7 @@
    Part of Scryer Prolog.
 
    This library provides the nonterminal format_//2 to describe
-   formatted strings. format/2 is provided for impure output.
+   formatted strings. format/[2,3] are provided for impure output.
 
    Usage:
    ======
@@ -74,6 +74,7 @@
                    format/2,
                    format/3,
                    portray_clause/1,
+                   portray_clause/2,
                    listing/1
                   ]).
 
@@ -158,7 +159,7 @@ element_gluevar(glue(_,V), N, N) --> [V].
 
 cells([], Args, Tab, Es) -->
         (   { Args == [] } -> cell(Tab, Tab, Es)
-        ;   { domain_error(no_remaining_arguments, Args, format_//2) }
+        ;   { domain_error(empty_list, Args, format_//2) }
         ).
 cells([~,~|Fs], Args, Tab, Es) --> !,
         cells(Fs, Args, Tab, [chars("~")|Es]).
@@ -172,9 +173,11 @@ 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, [Arg|Args]) },
+        { numeric_argument(Fs0, Num, [d|Fs], Args0, [Arg0|Args]) },
         !,
-        { number_chars(Arg, Cs0) },
+        { Arg is Arg0, % evaluate compound expression
+          must_be(integer, Arg),
+          number_chars(Arg, Cs0) },
         (   { Num =:= 0 } -> { Cs = Cs0 }
         ;   { length(Cs0, L),
               (   L =< Num ->
@@ -216,12 +219,12 @@ cells([~|Fs0], Args0, Tab, Es) -->
 cells([~,s|Fs], [Arg|Args], Tab, Es) --> !,
         cells(Fs, Args, Tab, [chars(Arg)|Es]).
 cells([~,f|Fs], [Arg|Args], Tab, Es) --> !,
-        { number_chars(Arg, Chars) },
+        { 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]) },
         !,
-        { number_chars(Arg, Cs0),
+        { format_number_chars(Arg, Cs0),
           phrase(upto_what(Bs, .), Cs0, Cs),
           (   Num =:= 0 -> Chars = Bs
           ;   (   Cs = ['.'|Rest] ->
@@ -279,6 +282,10 @@ cells(Fs0, Args, Tab, Es) -->
           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).
 
@@ -327,7 +334,8 @@ pow10(D, N0-Pow0, N-Pow) :-
         N is N0 + D*10^Pow0,
         Pow is Pow0 + 1.
 
-integer_to_radix(I, R, Which, Cs) :-
+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) ->
@@ -361,28 +369,16 @@ digits(uppercase, "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ").
 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 
 format(Fs, Args) :-
-        phrase(format_(Fs, Args), Cs),
-        maplist(write, Cs).
+        current_output(Stream),
+        format(Stream, Fs, Args).
 
 format(Stream, Fs, Args) :-
         phrase(format_(Fs, Args), Cs),
-        (   stream_property(Stream, type(binary)) ->
-            % maplist(char_code, Cs, Bytes) is currently a lot slower
-            % than first converting Cs to an atom, and then to codes.
-            % In the future, we can ideally avoid creating an atom here,
-            % since an atom leaves traces in the system.
-            atom_chars(A, Cs),
-            atom_codes(A, Bytes),
-            (   member(NonByte, Bytes), NonByte > 255 ->
-                char_code(Char, NonByte),
-                throw(error(representation_error(Char), format/3))
-            ;   true
-            ),
-            % For binary streams, we use a specialised internal predicate
-            % that uses only a single "write" operation for efficiency.
-            '$put_bytes'(Stream, Bytes)
-        ;   maplist(put_char(Stream), Cs)
-        ).
+        % we use a specialised internal predicate that uses only a
+        % single "write" operation for efficiency. It is equivalent to
+        % maplist(put_char(Stream), Cs). It also works for binary streams.
+        '$put_chars'(Stream, Cs),
+        flush_output(Stream).
 
 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 ?- phrase(cells("hello", [], 0, []), Cs).
@@ -458,8 +454,12 @@ aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 
 portray_clause(Term) :-
+        current_output(Out),
+        portray_clause(Out, Term).
+
+portray_clause(Stream, Term) :-
         phrase(portray_clause_(Term), Ls),
-        maplist(write, Ls).
+        format(Stream, "~s", [Ls]).
 
 portray_clause_(Term) -->
         { term_variables(Term, Vs),

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/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/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/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

@@ -6,7 +6,16 @@
                     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) ->
@@ -23,10 +32,10 @@ socket_client_open(Addr, Stream, Options) :-
     ;
        throw(error(type_error(socket_address, Addr), socket_client_open/3))
     ),
-    builtins:parse_stream_options(Options,
-                                  [Alias, EOFAction, Reposition, Type],
-                                  socket_client_open/3),
-    '$socket_client_open'(Address, Port, Stream, Alias, EOFAction, Reposition, Type).
+    parse_socket_options(Options,
+                         [Alias, EOFAction, Reposition, TLS, Type],
+                         socket_client_open/3),
+    '$socket_client_open'(Address, Port, Stream, Alias, EOFAction, Reposition, Type, TLS).
 
 
 socket_server_open(Addr, ServerSocket) :-

src/lib/tabling.pl

@@ -8,12 +8,12 @@
 	    op(1150, fx, table)
 	  ]).
 
-:- use_module('tabling/double_linked_list').
-:- use_module('tabling/table_data_structure').
-:- use_module('tabling/batched_worklist').
-:- use_module('tabling/wrapper').
-:- use_module('tabling/global_worklist').
-:- use_module('tabling/table_link_manager').
+:- use_module(library(tabling/double_linked_list)).
+:- use_module(library(tabling/table_data_structure)).
+:- use_module(library(tabling/batched_worklist)).
+:- use_module(library(tabling/wrapper)).
+:- use_module(library(tabling/global_worklist)).
+:- use_module(library(tabling/table_link_manager)).
 
 :- use_module(library(cont)).
 :- use_module(library(lists)).

src/lib/tabling/batched_worklist.pl

@@ -45,8 +45,8 @@
 	    wkl_worklist_work_done/1			% +WorkList
 	  ]).
 
-:- use_module(global_worklist).
-:- use_module(double_linked_list).
+:- use_module(library(tabling/global_worklist)).
+:- use_module(library(tabling/double_linked_list)).
 
 :- use_module(library(atts)).
 :- use_module(library(lists)).

src/lib/tabling/table_data_structure.pl

@@ -15,8 +15,8 @@
 	    get_nb_identifiers/3                % +Table, -NbWorklistID, -NbAnswerTreeID
 	  ]).
 
-:- use_module(table_link_manager).
-:- use_module(trie).
+:- use_module(library(tabling/table_link_manager)).
+:- use_module(library(tabling/trie)).
 
 /*  Part of SWI-Prolog
 
@@ -53,7 +53,7 @@
     POSSIBILITY OF SUCH DAMAGE.
 */
 
-:- use_module(batched_worklist).
+:- use_module(library(tabling/batched_worklist)).
 
 :- use_module(library(atts)).
 :- use_module(library(gensym)).

src/lib/tabling/table_link_manager.pl

@@ -47,7 +47,7 @@
 :- use_module(library(iso_ext)).
 :- use_module(library(terms)).
 
-:- use_module(trie).
+:- use_module(library(tabling/trie)).
 
 :- attribute trie_table_link/1.
 

src/lib/tabling/trie.pl

@@ -66,7 +66,7 @@
 % p_trie_arity_univ(+Term,-FunctorData,-ArgumentsList).
 p_trie_arity_univ(Term,functor_data(Name,Arity),Arguments) :-
   (  var(Term) ->
-     Name = var,
+     Name = Term,
      Arity = 0,
      Arguments = []
   ;  Term =.. [Name|Arguments],

src/lib/time.pl

@@ -0,0 +1,129 @@
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   Written 2020 by Markus Triska (triska@metalevel.at)
+   Part of Scryer Prolog.
+
+   This library provides predicates for reasoning about time.
+
+   current_time(T) yields the current system time in an opaque form,
+   called a time stamp. Use format_time//2 to describe strings that
+   contain attributes of the time stamp.
+
+   The nonterminal format_time//2 describes a list of characters that
+   are formatted according to a format string. Usage:
+
+     phrase(format_time(FormatString, TimeStamp), Cs)
+
+   TimeStamp represents a moment in time in an opaque form, as for
+   example obtained by current_time/1.
+
+   FormatString is a list of characters that are interpreted literally,
+   except for the following specifiers (and possibly more in the future):
+
+     %Y    year of the time stamp. Example: 2020.
+     %m    month number (01-12), zero-padded to 2 digits
+     %d    day number (01-31), zero-padded to 2 digits
+     %H    hour number (00-24), zero-padded to 2 digits
+     %M    minute number (00-59), zero-padded to 2 digits
+     %S    second number (00-60), zero-padded to 2 digits
+     %b    abbreviated month name, always 3 letters
+     %a    abbreviated weekday name, always 3 letters
+     %A    full weekday name
+     %j    day of the year (001-366), zero-padded to 3 digits
+     %%    the literal %
+
+   Example:
+
+     ?- current_time(T), phrase(format_time("%d.%m.%Y (%H:%M:%S)", T), Cs).
+        T = [...], Cs = "11.06.2020 (00:24:32)"
+     ;  false.
+
+   sleep(S) sleeps for S seconds (a floating point number).
+
+   time(Goal) reports the execution time of Goal.
+
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+:- module(time, [max_sleep_time/1, sleep/1, time/1, current_time/1, format_time//2]).
+
+:- use_module(library(format)).
+:- use_module(library(iso_ext)).
+:- use_module(library(error)).
+:- use_module(library(dcgs)).
+:- use_module(library(lists)).
+:- use_module(library(charsio), [read_term_from_chars/2]).
+
+current_time(T) :-
+        '$current_time'(T0),
+        read_term_from_chars(T0, T).
+
+format_time([], _) --> [].
+format_time(['%','%'|Fs], T) --> !, "%", format_time(Fs, T).
+format_time(['%',Spec|Fs], T) --> !,
+        (   { member(Spec=Value, T) } ->
+            list(Value)
+        ;   { domain_error(time_specifier, Spec, format_time//2) }
+        ),
+        format_time(Fs, T).
+format_time([F|Fs], T) --> [F], format_time(Fs, T).
+
+list([]) --> [].
+list([L|Ls]) --> [L], list(Ls).
+
+max_sleep_time(0xfffffffffffffbff).
+
+sleep(T) :-
+    builtins:must_be_number(T, sleep),
+    (   T < 0 ->
+        domain_error(not_less_than_zero, T, sleep/1)
+    ;   max_sleep_time(N), T > N ->
+        throw(error(representation_error(max_sleep_time), sleep/1))
+    ;   '$sleep'(T)
+    ).
+
+
+% '$cpu_now' can be replaced by statistics/2 once that is implemented.
+
+time(Goal) :-
+        '$cpu_now'(T0),
+        setup_call_cleanup(true,
+                           (   Goal,
+                               report_time(T0)
+                           ),
+                           report_time(T0)).
+
+report_time(T0) :-
+        '$cpu_now'(T),
+        Time is T - T0,
+        (   bb_get('$first_answer', true) ->
+            format("   % CPU time: ~3f seconds~n", [Time])
+        ;   format("% CPU time: ~3f seconds~n   ", [Time])
+        ).
+
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+?- time((true;false)).
+   % CPU time: 0.000 seconds
+   true
+;  % CPU time: 0.001 seconds
+   false.
+
+:- time(use_module(library(clpz))).
+   % CPU time: 2.762 seconds
+   true
+;  false.
+
+:- time(use_module(library(lists))).
+   % CPU time: 0.000 seconds
+   true
+;  % CPU time: 0.001 seconds
+   false.
+
+?- time(member(X, [a,b,c])).
+   % CPU time: 0.000 seconds
+   X = a
+;  % CPU time: 0.002 seconds
+   X = b
+;  % CPU time: 0.004 seconds
+   X = c
+;  % CPU time: 0.007 seconds
+   false.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

src/lib/xpath.pl

@@ -0,0 +1,642 @@
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   The original copyright and licence information is shown below.
+
+   Adapted in June 2020 by Markus Triska (triska@metalevel.at)
+   Part of Scryer Prolog.
+
+   In order to improve portability and reliability of this library, I
+   have changed various parts of the original code to make it
+   conforming to the Prolog ISO standard. I have removed all
+   occurrences of proprietary non-standard ad hoc data types.
+
+   In Scryer Prolog, we represent strings as lists of characters.
+   This makes them amenable to processing with DCGs and other
+   built-in mechanisms such as existing predicates on lists.
+   Scryer Prolog represents lists of characters very compactly,
+   making it an ideal representation for large amounts of text. It
+   fully conforms to the ISO standard and is very portable.
+
+   This library is intended to be used in tandem with load_html/3
+   from library(sgml), which creates DOM trees from markup documents.
+   It can be combined with http_open/3 from library(http/http_open)
+   to read such documents directly from network connections.
+
+   For instance, to inspect all links to Prolog files (*.pl) on
+   Scryer Prolog's project page, we can use:
+
+      :- use_module(library(http/http_open)).
+      :- use_module(library(sgml)).
+      :- use_module(library(lists)).
+      :- use_module(library(xpath)).
+
+      link_to_pl_file(File) :-
+          http_open("https://github.com/mthom/scryer-prolog", S, []),
+          load_html(stream(S), DOM, []),
+          xpath(DOM, //a(@href), File),
+          append(_, ".pl", File).
+
+   Yielding:
+
+      ?- link_to_pl_file(File).
+      %@    File = "/mthom/scryer-prolog/blob/master/src/lib/tabling.pl"
+      %@ ;  File = "/mthom/scryer-prolog/blob/master/src/lib/dif.pl"
+      %@ ;  File = "/mthom/scryer-prolog/blob/master/src/lib/freeze.pl"
+      %@ ;  ...
+
+   Parts of the original functionality may not yet work. Please
+   consider such parts opportunities for improvements, and file
+   issues in case you need additional features.
+
+   The original copyright information follows.
+
+   ======================================================================
+
+
+    Author:        Jan Wielemaker
+    E-mail:        J.Wielemaker@vu.nl
+    WWW:           http://www.swi-prolog.org
+    Copyright (c)  2009-2019, University of Amsterdam
+                              VU University Amsterdam
+                              CWI, Amsterdam
+    All rights reserved.
+
+    Redistribution and use in source and binary forms, with or without
+    modification, are permitted provided that the following conditions
+    are met:
+
+    1. Redistributions of source code must retain the above copyright
+       notice, this list of conditions and the following disclaimer.
+
+    2. Redistributions in binary form must reproduce the above copyright
+       notice, this list of conditions and the following disclaimer in
+       the documentation and/or other materials provided with the
+       distribution.
+
+    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+    POSSIBILITY OF SUCH DAMAGE.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+:- module(xpath,
+          [ xpath/3,                    % +DOM, +Spec, -Value
+            xpath_chk/3,                % +DOM, +Spec, -Value
+
+            op(400, fx, //),
+            op(400, fx, /),
+            op(200, fy, @)
+          ]).
+
+:- use_module(library(lists),[member/2,memberchk/2]).
+:- use_module(library(error)).
+:- use_module(library(dcgs)).
+:- use_module(library(si)).
+
+/** <module> Select nodes in an XML DOM
+
+The library xpath.pl provides predicates to select nodes from an XML DOM
+tree as produced by library(sgml) based  on descriptions inspired by the
+XPath language.
+
+The   predicate   xpath/3   selects   a   sub-structure   of   the   DOM
+non-deterministically based on an  XPath-like   specification.  Not  all
+selectors of XPath are implemented, but the ability to mix xpath/3 calls
+with arbitrary Prolog code  provides  a   powerful  tool  for extracting
+information from XML parse-trees.
+
+@see http://www.w3.org/TR/xpath
+*/
+
+element_name(element(Name,_,_), Name).
+element_attributes(element(_,Attributes,_), Attributes).
+element_content(element(_,_,Content), Content).
+
+%!  xpath_chk(+DOM, +Spec, ?Content) is semidet.
+%
+%   Semi-deterministic version of xpath/3.
+
+xpath_chk(DOM, Spec, Content) :-
+    xpath(DOM, Spec, Content),
+    !.
+
+%!  xpath(+DOM, +Spec, ?Content) is nondet.
+%
+%   Match an element in a DOM structure.   The syntax is inspired by
+%   XPath, using () rather than  []   to  select  inside an element.
+%   First we can construct paths using / and //:
+%
+%       $ =|//|=Term :
+%       Select any node in the DOM matching term.
+%       $ =|/|=Term :
+%       Match the root against Term.
+%       $ Term :
+%       Select the immediate children of the root matching Term.
+%
+%   The Terms above are of type   _callable_.  The functor specifies
+%   the element name. The element name   '*'  refers to any element.
+%   The name =self= refers to the   top-element  itself and is often
+%   used for processing matches of an  earlier xpath/3 query. A term
+%   NS:Term refers to an XML  name   in  the  namespace NS. Optional
+%   arguments specify additional  constraints   and  functions.  The
+%   arguments are processed from left  to right. Defined conditional
+%   argument values are:
+%
+%       $ index(?Index) :
+%       True if the element is the Index-th child of its parent,
+%       where 1 denotes the first child. Index can be one of:
+%         $ `Var` :
+%         `Var` is unified with the index of the matched element.
+%         $ =last= :
+%         True for the last element.
+%         $ =last= - `IntExpr` :
+%         True for the last-minus-nth element. For example,
+%         `last-1` is the element directly preceding the last one.
+%         $ `IntExpr` :
+%         True for the element whose index equals `IntExpr`.
+%       $ Integer :
+%       The N-th element with the given name, with 1 denoting the
+%       first element. Same as index(Integer).
+%       $ =last= :
+%       The last element with the given name. Same as
+%       index(last).
+%       $ =last= - IntExpr :
+%       The IntExpr-th element before the last.
+%       Same as index(last-IntExpr).
+%
+%   Defined function argument values are:
+%
+%       $ =self= :
+%       Evaluate to the entire element
+%       $ =content= :
+%       Evaluate to the content of the element (a list)
+%       $ =text= :
+%       Evaluates to all text from the sub-tree, represented
+%       as a list of characters.
+%       $ `text(atom)` :
+%       Evaluates to all text from the sub-tree as an atom.
+%       $ =normalize_space= :
+%       As =text=, but uses normalize_space/2 to normalise
+%       white-space in the output
+%       $ =number= :
+%       Extract an integer or float from the value.  Ignores
+%       leading and trailing white-space
+%       $ =|@|=Attribute :
+%       Evaluates to the value of the given attribute.  Attribute
+%       can be a compound term. In this case the functor name
+%       denotes the element and arguments perform transformations
+%       on the attribute value.  Defined transformations are:
+%
+%         - number
+%         Translate the value into a number using
+%         xsd_number_chars/2.
+%         - integer
+%         As `number`, but subsequently transform the value
+%         into an integer using the round/1 function.
+%         - float
+%         As `number`, but subsequently transform the value
+%         into a float using the float/1 function.
+%         - lower
+%         Translate the value to lower case, preserving
+%         the type.
+%         - upper
+%         Translate the value to upper case, preserving
+%         the type.
+%
+%   In addition, the argument-list can be _conditions_:
+%
+%       $ Left = Right :
+%       Succeeds if the left-hand unifies with the right-hand.
+%       If the left-hand side is a function, this is evaluated.
+%       The right-hand side is _never_ evaluated, and thus the
+%       condition `content = content` defines that the content
+%       of the element is the atom `content`.
+%       The functions `lower_case` and `upper_case` can be applied
+%       to Right (see example below).
+%       $ contains(Haystack, Needle) :
+%       Succeeds if Needle is a sub-list of Haystack.
+%       $ XPath :
+%       Succeeds if XPath matches in the currently selected
+%       sub-DOM.  For example, the following expression finds
+%       an =h3= element inside a =div= element, where the =div=
+%       element itself contains an =h2= child with a =strong=
+%       child.
+%
+%         ==
+%         //div(h2/strong)/h3
+%         ==
+%
+%       This is equivalent to the conjunction of XPath goals below.
+%
+%         ==
+%            ...,
+%            xpath(DOM, //(div), Div),
+%            xpath(Div, h2/strong, _),
+%            xpath(Div, h3, Result)
+%         ==
+%
+%   **Examples**:
+%
+%   Match each table-row in DOM:
+%
+%       ==
+%       xpath(DOM, //tr, TR)
+%       ==
+%
+%   Match the last cell  of  each   tablerow  in  DOM.  This example
+%   illustrates that a result can be the input of subsequent xpath/3
+%   queries. Using multiple queries  on   the  intermediate  TR term
+%   guarantee that all results come from the same table-row:
+%
+%       ==
+%       xpath(DOM, //tr, TR),
+%       xpath(TR,  /td(last), TD)
+%       ==
+%
+%   Match each =href= attribute in an <a> element
+%
+%       ==
+%       xpath(DOM, //a(@href), HREF)
+%       ==
+%
+%   Suppose we have a table containing  rows where each first column
+%   is the name of a product with a   link to details and the second
+%   is the price (a number).  The   following  predicate matches the
+%   name, URL and price:
+%
+%       ==
+%       product(DOM, Name, URL, Price) :-
+%           xpath(DOM, //tr, TR),
+%           xpath(TR, td(1), C1),
+%           xpath(C1, /self(normalize_space), Name),
+%           xpath(C1, a(@href), URL),
+%           xpath(TR, td(2, number), Price).
+%       ==
+%
+%   Suppose we want to select  books   with  genre="thriller" from a
+%   tree containing elements =|<book genre=...>|=
+%
+%       ==
+%       thriller(DOM, Book) :-
+%           xpath(DOM, //book(@genre=thiller), Book).
+%       ==
+%
+%   Match the elements =|<table align="center">|= _and_ =|<table
+%   align="CENTER">|=:
+%
+%       ```prolog
+%           //table(@align(lower) = center)
+%       ```
+%
+%   Get the `width` and `height` of a `div` element as a number,
+%   and the `div` node itself:
+%
+%       ==
+%           xpath(DOM, //div(@width(number)=W, @height(number)=H), Div)
+%       ==
+%
+%   Note that `div` is an infix operator, so parentheses must be
+%   used in cases like the following:
+%
+%       ==
+%           xpath(DOM, //(div), Div)
+%       ==
+
+xpath(DOM, Spec, Content) :-
+    in_dom(Spec, DOM, Content).
+
+in_dom(//Spec, DOM, Value) :-
+    !,
+    element_spec(Spec, Name, Modifiers),
+    sub_dom(I, Len, Name, E, DOM),
+    modifiers(Modifiers, I, Len, E, Value).
+in_dom(/Spec, E, Value) :-
+    !,
+    element_spec(Spec, Name, Modifiers),
+    (   Name == self
+    ->  true
+    ;   element_name(E, Name)
+    ),
+    modifiers(Modifiers, 1, 1, E, Value).
+in_dom(A/B, DOM, Value) :-
+    !,
+    in_dom(A, DOM, Value0),
+    in_dom(B, Value0, Value).
+in_dom(A//B, DOM, Value) :-
+    !,
+    in_dom(A, DOM, Value0),
+    in_dom(//B, Value0, Value).
+in_dom(Spec, element(_, _, Content), Value) :-
+    element_spec(Spec, Name, Modifiers),
+    count_named_elements(Content, Name, CLen),
+    CLen > 0,
+    nth_element(N, Name, E, Content),
+    modifiers(Modifiers, N, CLen, E, Value).
+
+element_spec(Var, _, _) :-
+    var(Var),
+    !,
+    instantiation_error(Var).
+element_spec(NS:Term, NS:Name, Modifiers) :-
+    !,
+    callable_name_arguments(Term, Name0, Modifiers),
+    star(Name0, Name).
+element_spec(Term, Name, Modifiers) :-
+    !,
+    callable_name_arguments(Term, Name0, Modifiers),
+    star(Name0, Name).
+
+callable_name_arguments(Atom, Name, Arguments) :-
+    atom(Atom),
+    !,
+    Name = Atom, Arguments = [].
+callable_name_arguments(Compound, Name, Arguments) :-
+    Compound =.. [Name|Arguments].
+
+
+star(*, _) :- !.
+star(Name, Name).
+
+
+%!  sub_dom(-Index, -Count, +Name, -Sub, +DOM) is nondet.
+%
+%   Sub is a node in DOM with Name.
+%
+%   @param Count    is the total number of nodes in the content
+%                   list Sub appears that have the same name.
+%   @param Index    is the 1-based index of Sub of nodes with
+%                   Name.
+
+sub_dom(1, 1, Name, DOM, DOM) :-
+    element_name(DOM, Name0),
+    \+ Name \= Name0.
+sub_dom(N, Len, Name, E, element(_,_,Content)) :-
+    !,
+    sub_dom_2(N, Len, Name, E, Content).
+sub_dom(N, Len, Name, E, Content) :-
+    list_si(Content),
+    sub_dom_2(N, Len, Name, E, Content).
+
+sub_dom_2(N, Len, Name, Element, Content) :-
+    (   count_named_elements(Content, Name, Len),
+        nth_element(N, Name, Element, Content)
+    ;   member(element(_,_,C2), Content),
+        sub_dom_2(N, Len, Name, Element, C2)
+    ).
+
+
+%!  count_named_elements(+Content, +Name, -Count) is det.
+%
+%   Count is the number of nodes with Name in Content.
+
+count_named_elements(Content, Name, Count) :-
+    count_named_elements(Content, Name, 0, Count).
+
+count_named_elements([], _, Count, Count).
+count_named_elements([element(Name,_,_)|T], Name0, C0, C) :-
+    \+ Name \= Name0,
+    !,
+    C1 is C0+1,
+    count_named_elements(T, Name0, C1, C).
+count_named_elements([_|T], Name, C0, C) :-
+    count_named_elements(T, Name, C0, C).
+
+
+%!  nth_element(?N, +Name, -Element, +Content:list) is nondet.
+%
+%   True if Element is the N-th element with name in Content.
+
+nth_element(N, Name, Element, Content) :-
+    nth_element_(1, N, Name, Element, Content).
+
+nth_element_(I, N, Name, E, [H|T]) :-
+    element_name(H, Name0),
+    \+ Name \= Name0,
+    !,
+    (   N = I,
+        E = H
+    ;   I2 is I + 1,
+        (   nonvar(N), I2 > N
+        ->  !, fail
+        ;   true
+        ),
+        nth_element_(I2, N, Name, E, T)
+    ).
+nth_element_(I, N, Name, E, [_|T]) :-
+    nth_element_(I, N, Name, E, T).
+
+
+%!  modifiers(+Modifiers, +I, +Clen, +DOM, -Value)
+%
+%
+
+modifiers([], _, _, Value, Value).
+modifiers([H|T], I, L, Value0, Value) :-
+    modifier(H, I, L, Value0, Value1),
+    modifiers(T, I, L, Value1, Value).
+
+modifier(M, _, _, _, _) :-
+    var(M),
+    !,
+    instantiation_error(M).
+modifier(Index, I, L, Value0, Value) :-
+    implicit_index_modifier(Index),
+    !,
+    Value = Value0,
+    index_modifier(Index, I, L).
+modifier(index(Index), I, L, Value, Value) :-
+    !,
+    index_modifier(Index, I, L).
+modifier(Function, _, _, In, Out) :-
+    xpath_function(Function),
+    !,
+    xpath_function(Function, In, Out).
+modifier(Function, _, _, In, Out) :-
+    xpath_condition(Function, In),
+    Out = In.
+
+implicit_index_modifier(I) :-
+    integer(I),
+    !.
+implicit_index_modifier(last).
+implicit_index_modifier(last-_Expr).
+
+index_modifier(Var, I, _L) :-
+    var(Var),
+    !,
+    Var = I.
+index_modifier(last, I, L) :-
+    !,
+    I =:= L.
+index_modifier(last-Expr, I, L) :-
+    !,
+    I =:= L-Expr.
+index_modifier(N, I, _) :-
+    N =:= I.
+
+xpath_function(self, DOM, DOM).                                % self
+xpath_function(content, Element, Value) :-                     % content
+    element_content(Element, Value).
+xpath_function(text, DOM, Text) :-                             % text
+    text_of_dom(DOM, chars, Text).
+xpath_function(text(As), DOM, Text) :-                         % text(atom)
+    text_of_dom(DOM, As, Text).
+xpath_function(normalize_space, DOM, Text) :-                  % normalize_space
+    text_of_dom(DOM, chars, Text0),
+    normalize_space(Text0, Text).
+xpath_function(number, DOM, Number) :-                         % number
+    text_of_dom(DOM, chars, Text0),
+    normalize_space(Text0, Text),
+    catch(xsd_number_chars(Number, Text), _, fail).
+xpath_function(@Name, element(_, Attrs, _), Value) :-          % @Name
+    (   atom(Name)
+    ->  memberchk(Name=Value, Attrs)
+    ;   compound(Name)
+    ->  Name =.. [AName|AOps],
+        memberchk(AName=Value0, Attrs),
+        translate_attribute(AOps, Value0, Value)
+    ;   member(Name=Value, Attrs)
+    ).
+xpath_function(quote(Value), _, Value).                         % quote(Value)
+
+xpath_function(self).
+xpath_function(content).
+xpath_function(text).
+xpath_function(text(_)).
+xpath_function(normalize_space).
+xpath_function(number).
+xpath_function(@_).
+xpath_function(quote(_)).
+
+translate_attribute([], Value, Value).
+translate_attribute([H|T], Value0, Value) :-
+    translate_attr(H, Value0, Value1),
+    translate_attribute(T, Value1, Value).
+
+translate_attr(number, Value0, Value) :-
+    xsd_number_chars(Value, Value0).
+translate_attr(integer, Value0, Value) :-
+    xsd_number_chars(Value1, Value0),
+    Value is round(Value1).
+translate_attr(float, Value0, Value) :-
+    xsd_number_chars(Value1, Value0),
+    Value is float(Value1).
+% The implementation of these translations is left for later.
+% translate_attr(lower, Value0, Value) :- ...
+% translate_attr(upper, Value0, Value) :- ...
+
+xpath_condition(Left = Right, Value) :-                        % =
+    !,
+    var_or_function(Left, Value, LeftValue),
+    process_equality(LeftValue, Right).
+xpath_condition(contains(Haystack, Needle), Value) :-          % contains(Haystack, Needle)
+    !,
+    val_or_function(Haystack, Value, HaystackValue),
+    val_or_function(Needle, Value, NeedleValue),
+    (   phrase((list(_),list(NeedleValue),list(_)), HaystackValue)
+    ->  true
+    ).
+xpath_condition(Spec, Dom) :-
+    in_dom(Spec, Dom, _).
+
+
+%!  process_equality(+Left, +Right) is semidet.
+%
+%   Provides (very) partial support for XSLT   functions that can be
+%   applied according to the XPath 2 specification.
+%
+%   For example the XPath expression  in   [1],  and  the equivalent
+%   Prolog expression in [2], would both   match the HTML element in
+%   [3].
+%
+%     ==
+%     [1] //table[align=lower-case(center)]
+%     [2] //table(@align=lower_case(center))
+%     [3] <table align="CENTER">
+%     ==
+
+process_equality(Left, Right) :-
+    var(Right),
+    !,
+    Left = Right.
+process_equality(Left, lower_case(Right)) :-
+    !,
+    downcase_atom(Left, Right).
+process_equality(Left, upper_case(Right)) :-
+    !,
+    upcase_atom(Left, Right).
+process_equality(Left, Right) :-
+    Left = Right.
+
+
+var_or_function(Arg, _, Arg) :-
+    var(Arg),
+    !.
+var_or_function(Func, Value0, Value) :-
+    xpath_function(Func),
+    !,
+    xpath_function(Func, Value0, Value).
+var_or_function(Value, _, Value).
+
+val_or_function(Arg, _, Arg) :-
+    var(Arg),
+    !,
+    instantiation_error(Arg).
+val_or_function(Func, Value0, Value) :-                         % TBD
+    xpath_function(Func, Value0, Value),
+    !.
+val_or_function(Value, _, Value).
+
+
+%!  text_of_dom(+DOM, +As, -Text:(chars | atom)) is det.
+%
+%   Text is the joined textual content of DOM.
+
+text_of_dom(DOM, As, Text) :-
+    phrase(text_of(DOM), Text0),
+    (   As == chars ->
+        Text = Text0
+    ;   As == atom ->
+        atom_chars(Text, Text0)
+    ;   domain_error(As, atom_or_chars, xpath)
+    ).
+
+text_of(element(_,_,Content)) -->
+    text_of_list(Content).
+text_of([]) -->
+    [].
+text_of([H|T]) -->
+    text_of(H),
+    text_of(T).
+
+
+text_of_list([]) -->
+    [].
+text_of_list([H|T]) -->
+    text_of_1(H),
+    text_of_list(T).
+
+
+text_of_1(element(_,_,Content)) -->
+        text_of_list(Content).
+text_of_1([C|Cs]) --> list([C|Cs]).
+
+list([]) --> [].
+list([L|Ls]) --> [L], list(Ls).
+
+% For now, we use number_chars/2 to parse XML numbers.
+% If the need arises, we can extend this to additional
+% float constants and syntax that may occur in XML files.
+
+xsd_number_chars(Number, Chars) :-
+        number_chars(Number, Chars).
+
+normalize_space(Text0, Text) :-
+        Text0 = Text.           % no conversion for the moment.

src/machine/arithmetic_ops.rs

@@ -2,14 +2,14 @@ use crate::divrem::*;
 
 use crate::prolog_parser::ast::*;
 
-use crate::prolog::arithmetic::*;
-use crate::prolog::clause_types::*;
-use crate::prolog::forms::*;
-use crate::prolog::machine::machine_errors::*;
-use crate::prolog::machine::machine_indices::*;
-use crate::prolog::machine::machine_state::*;
-use crate::prolog::ordered_float::*;
-use crate::prolog::rug::{Integer, Rational};
+use crate::arithmetic::*;
+use crate::clause_types::*;
+use crate::forms::*;
+use crate::machine::machine_errors::*;
+use crate::machine::machine_indices::*;
+use crate::machine::machine_state::*;
+use crate::ordered_float::*;
+use crate::rug::{Integer, Rational};
 
 use std::cmp;
 use std::convert::TryFrom;
@@ -143,12 +143,10 @@ impl MachineState {
 
     pub(crate)
     fn arith_eval_by_metacall(&self, r: RegType) -> Result<Number, MachineStub> {
-        let a = self[r].clone();
-
-        let caller = MachineError::functor_stub(clause_name!("(is)"), 2);
+        let caller = MachineError::functor_stub(clause_name!("is"), 2);
         let mut interms: Vec<Number> = Vec::with_capacity(64);
 
-        for addr in self.post_order_iter(a) {
+        for addr in self.post_order_iter(self[r]) {
             match self.heap.index_addr(&addr).as_ref() {
                 &HeapCellValue::NamedStr(2, ref name, _) => {
                     let a2 = interms.pop().unwrap();
@@ -159,7 +157,7 @@ impl MachineState {
                         "-" => interms.push(try_numeric_result!(self, a1 - a2, caller)?),
                         "*" => interms.push(try_numeric_result!(self, a1 * a2, caller)?),
                         "/" => interms.push(self.div(a1, a2)?),
-                        "**" => interms.push(self.pow(a1, a2, "(is)")?),
+                        "**" => interms.push(self.pow(a1, a2, "is")?),
                         "^" => interms.push(self.int_pow(a1, a2)?),
                         "max" => interms.push(self.max(a1, a2)?),
                         "min" => interms.push(self.min(a1, a2)?),
@@ -191,7 +189,16 @@ impl MachineState {
                         "atan2" => interms.push(Number::Float(OrderedFloat(self.atan2(a1, a2)?))),
                         "gcd" => interms.push(self.gcd(a1, a2)?),
                         _ => {
-                            return Err(self.error_form(MachineError::instantiation_error(), caller))
+                            let evaluable_stub = MachineError::functor_stub(name.clone(), 2);
+
+                            return Err(self.error_form(
+                                MachineError::type_error(
+                                    self.heap.h(),
+                                    ValidType::Evaluable,
+                                    evaluable_stub,
+                                ),
+                                caller,
+                            ));
                         }
                     }
                 }
@@ -219,7 +226,16 @@ impl MachineState {
                         "\\" => interms.push(self.bitwise_complement(a1)?),
                         "sign" => interms.push(self.sign(a1)),
                         _ => {
-                            return Err(self.error_form(MachineError::instantiation_error(), caller));
+                            let evaluable_stub = MachineError::functor_stub(name.clone(), 1);
+
+                            return Err(self.error_form(
+                                MachineError::type_error(
+                                    self.heap.h(),
+                                    ValidType::Evaluable,
+                                    evaluable_stub,
+                                ),
+                                caller,
+                            ));
                         }
                     }
                 }
@@ -241,12 +257,44 @@ impl MachineState {
                 &HeapCellValue::Atom(ref name, _) if name.as_str() == "pi" => {
                     interms.push(Number::Float(OrderedFloat(f64::consts::PI)))
                 }
-                _ => {
+                &HeapCellValue::NamedStr(arity, ref name, _) => {
+                    let evaluable_stub = MachineError::functor_stub(name.clone(), arity);
+
+                    return Err(self.error_form(
+                        MachineError::type_error(
+                            self.heap.h(),
+                            ValidType::Evaluable,
+                            evaluable_stub,
+                        ),
+                        caller,
+                    ));
+                }
+                &HeapCellValue::Atom(ref name, _) => {
+                    let evaluable_stub = MachineError::functor_stub(name.clone(), 0);
+
+                    return Err(self.error_form(
+                        MachineError::type_error(
+                            self.heap.h(),
+                            ValidType::Evaluable,
+                            evaluable_stub,
+                        ),
+                        caller,
+                    ));
+                }
+                &HeapCellValue::Addr(addr) if addr.is_ref() => {
                     return Err(self.error_form(
                         MachineError::instantiation_error(),
                         caller,
                     ));
                 }
+                val => {
+                    return Err(self.type_error(
+                        ValidType::Number,
+                        val.context_free_clone(),
+                        clause_name!("is"),
+                        2,
+                    ));
+                }
             }
         }
 
@@ -377,7 +425,7 @@ impl MachineState {
 
     pub(crate)
     fn atan2(&self, n1: Number, n2: Number) -> Result<f64, MachineStub> {
-        let stub = MachineError::functor_stub(clause_name!("(is)"), 2);
+        let stub = MachineError::functor_stub(clause_name!("is"), 2);
 
         if n1.is_zero() && n2.is_zero() {
             Err(self.error_form(MachineError::evaluation_error(EvalError::Undefined), stub))
@@ -392,13 +440,13 @@ impl MachineState {
     pub(crate)
     fn int_pow(&self, n1: Number, n2: Number) -> Result<Number, MachineStub> {
         if n1.is_zero() && n2.is_negative() {
-            let stub = MachineError::functor_stub(clause_name!("(is)"), 2);
+            let stub = MachineError::functor_stub(clause_name!("is"), 2);
             return Err(self.error_form(MachineError::evaluation_error(EvalError::Undefined), stub));
         }
 
         match (n1, n2) {
             (Number::Fixnum(n1), Number::Fixnum(n2)) => {
-                if n1 != 1 && n2 < -1 {
+                if !(n1 == 1 || n1 == 0 || n1 == -1) && n2 < 0 {
                     let n = Number::from(n1);
                     let stub = MachineError::functor_stub(clause_name!("^"), 2);
 
@@ -424,7 +472,7 @@ impl MachineState {
                 }
             }
             (Number::Fixnum(n1), Number::Integer(n2)) => {
-                if n1 != 1 && &*n2 < &-1 {
+                if !(n1 == 1 || n1 == 0 || n1 == -1) && &*n2 < &0 {
                     let n = Number::from(n1);
                     let stub = MachineError::functor_stub(clause_name!("^"), 2);
 
@@ -442,7 +490,7 @@ impl MachineState {
                 }
             }
             (Number::Integer(n1), Number::Fixnum(n2)) => {
-                if &*n1 != &1 && n2 < -1 {
+                if !(&*n1 == &1 || &*n1 == &0 || &*n1 == &-1) && n2 < 0 {
                     let n = Number::Integer(n1);
                     let stub = MachineError::functor_stub(clause_name!("^"), 2);
 
@@ -460,7 +508,7 @@ impl MachineState {
                 }
             }
             (Number::Integer(n1), Number::Integer(n2)) => {
-                if &*n1 != &1 && &*n2 < &-1 {
+                if !(&*n1 == &1 || &*n1 == &0 || &*n1 == &-1) && &*n2 < &0 {
                     let n = Number::Integer(n1);
                     let stub = MachineError::functor_stub(clause_name!("^"), 2);
 
@@ -487,7 +535,7 @@ impl MachineState {
                 let f2 = self.float(n2)?;
 
                 if n1.is_negative() && f2 != f2.floor() {
-                    let stub = MachineError::functor_stub(clause_name!("(is)"), 2);
+                    let stub = MachineError::functor_stub(clause_name!("is"), 2);
                     return Err(
                         self.error_form(MachineError::evaluation_error(EvalError::Undefined), stub)
                     );
@@ -571,34 +619,7 @@ impl MachineState {
             return Err(self.error_form(MachineError::evaluation_error(EvalError::Undefined), stub));
         }
 
-        match (n1, n2) {
-            (Number::Fixnum(n1), Number::Fixnum(n2)) => {
-                if let Ok(n2) = u32::try_from(n2) {
-                    if let Some(result) = n1.checked_pow(n2) {
-                        return Ok(Number::from(result));
-                    }
-                }
-
-                let n1 = Integer::from(n1);
-                let n2 = Integer::from(n2);
-
-                Ok(Number::from(binary_pow(n1, &n2)))
-            }
-            (Number::Fixnum(n1), Number::Integer(n2)) => {
-                let n1 = Integer::from(n1);
-                Ok(Number::from(binary_pow(n1, n2.as_ref())))
-            }
-            (Number::Integer(n1), Number::Fixnum(n2)) => {
-                let n2 = Integer::from(n2);
-                Ok(Number::from(binary_pow(n1.as_ref().clone(), &n2)))
-            }
-            (Number::Integer(n1), Number::Integer(n2)) => {
-                Ok(Number::from(binary_pow(n1.as_ref().clone(), &*n2)))
-            }
-            (n1, n2) => {
-                self.float_pow(n1, n2)
-            }
-        }
+        self.float_pow(n1, n2)
     }
 
     #[inline]
@@ -607,7 +628,7 @@ impl MachineState {
     where
         FloatFn: Fn(f64) -> f64,
     {
-        let stub = MachineError::functor_stub(clause_name!("(is)"), 2);
+        let stub = MachineError::functor_stub(clause_name!("is"), 2);
 
         let f1 = try_numeric_result!(self, result_f(&n1, rnd_f), stub)?;
         let f1 = result_f(&Number::Float(OrderedFloat(f(f1))), rnd_f);
@@ -667,7 +688,7 @@ impl MachineState {
     pub(crate)
     fn sqrt(&self, n1: Number) -> Result<f64, MachineStub> {
         if n1.is_negative() {
-            let stub = MachineError::functor_stub(clause_name!("(is)"), 2);
+            let stub = MachineError::functor_stub(clause_name!("is"), 2);
             return Err(self.error_form(MachineError::evaluation_error(EvalError::Undefined), stub));
         }
 
@@ -677,7 +698,7 @@ impl MachineState {
     #[inline]
     pub(crate)
     fn float(&self, n: Number) -> Result<f64, MachineStub> {
-        let stub = MachineError::functor_stub(clause_name!("(is)"), 2);
+        let stub = MachineError::functor_stub(clause_name!("is"), 2);
         try_numeric_result!(self, result_f(&n, rnd_f), stub)
     }
 
@@ -705,7 +726,7 @@ impl MachineState {
 
     pub(crate)
     fn round(&self, n: Number) -> Result<Number, MachineStub> {
-        let stub = MachineError::functor_stub(clause_name!("(is)"), 2);
+        let stub = MachineError::functor_stub(clause_name!("is"), 2);
 
         let result = n + Number::Float(OrderedFloat(0.5f64));
         let result = try_numeric_result!(self, result, stub)?;

src/machine/attributed_variables.rs

@@ -1,5 +1,5 @@
-use crate::prolog::heap_iter::*;
-use crate::prolog::machine::*;
+use crate::heap_iter::*;
+use crate::machine::*;
 
 use crate::indexmap::IndexSet;
 

src/machine/code_repo.rs

@@ -1,13 +1,13 @@
-use crate::prolog::clause_types::*;
-use crate::prolog::codegen::*;
-use crate::prolog::debray_allocator::*;
-use crate::prolog::forms::*;
-use crate::prolog::instructions::*;
-use crate::prolog::machine::compile::*;
-use crate::prolog::machine::machine_errors::*;
-use crate::prolog::machine::machine_indices::*;
+use crate::clause_types::*;
+use crate::codegen::*;
+use crate::debray_allocator::*;
+use crate::forms::*;
+use crate::instructions::*;
+use crate::machine::compile::*;
+use crate::machine::machine_errors::*;
+use crate::machine::machine_indices::*;
 
-use indexmap::IndexSet;
+use crate::indexmap::IndexSet;
 
 use std::collections::VecDeque;
 use std::mem;

src/machine/code_walker.rs

@@ -1,4 +1,4 @@
-use crate::prolog::instructions::*;
+use crate::instructions::*;
 
 use std::collections::VecDeque;
 

src/machine/compile.rs

@@ -1,22 +1,22 @@
-use prolog_parser::ast::*;
-use prolog_parser::parser::get_desc;
-use prolog_parser::tabled_rc::TabledData;
+use crate::prolog_parser::ast::*;
+use crate::prolog_parser::parser::get_desc;
+use crate::prolog_parser::tabled_rc::TabledData;
 
-use crate::prolog::codegen::*;
-use crate::prolog::debray_allocator::*;
-use crate::prolog::forms::*;
-use crate::prolog::instructions::*;
-use crate::prolog::iterators::*;
-use crate::prolog::machine::code_walker::*;
-use crate::prolog::machine::machine_errors::*;
-use crate::prolog::machine::machine_indices::*;
-use crate::prolog::machine::term_expansion::ExpansionAdditionResult;
-use crate::prolog::machine::toplevel::*;
-use crate::prolog::machine::*;
+use crate::codegen::*;
+use crate::debray_allocator::*;
+use crate::forms::*;
+use crate::instructions::*;
+use crate::iterators::*;
+use crate::machine::code_walker::*;
+use crate::machine::machine_errors::*;
+use crate::machine::machine_indices::*;
+use crate::machine::term_expansion::ExpansionAdditionResult;
+use crate::machine::toplevel::*;
+use crate::machine::*;
 
-use indexmap::{IndexMap, IndexSet};
+use crate::indexmap::{IndexMap, IndexSet};
 
-use ref_thread_local::RefThreadLocal;
+use crate::ref_thread_local::RefThreadLocal;
 
 use std::cell::Cell;
 use std::collections::VecDeque;
@@ -469,6 +469,7 @@ impl ClauseCodeGenerator {
                             vec![Box::new(head.clone()), Box::new(tail.clone())],
                             None,
                         );
+
                         PredicateClause::Fact(clause, 0, 0)
                     })
                     .collect(),
@@ -601,12 +602,7 @@ fn load_library(
 ) -> Result<ClauseName, SessionError> {
     match LIBRARIES.borrow().get(name.as_str()) {
         Some(code) => {
-            let mut lib_path = current_dir();
-
-            lib_path.pop();
-            lib_path.push("lib");
-
-            let listing_src = ListingSource::from_file_and_path(name, lib_path);
+            let listing_src = ListingSource::User;
 
             load_module(
                 wam,

src/machine/copier.rs

@@ -1,5 +1,5 @@
-use crate::prolog::machine::machine_indices::*;
-use crate::prolog::machine::stack::*;
+use crate::machine::machine_indices::*;
+use crate::machine::stack::*;
 
 use std::mem;
 use std::ops::IndexMut;
@@ -104,7 +104,7 @@ impl<T: CopierTarget> CopyTermState<T> {
     fn copy_partial_string(&mut self, addr: usize, n: usize) {
         if let &HeapCellValue::Addr(Addr::PStrLocation(h, _)) = &self.target[addr] {
             if h >= self.old_h {
-                *self.value_at_scan() = HeapCellValue::Addr(Addr::PStrLocation(h, 0));
+                *self.value_at_scan() = HeapCellValue::Addr(Addr::PStrLocation(h, n));
                 self.scan += 1;
 
                 return;
@@ -114,14 +114,14 @@ impl<T: CopierTarget> CopyTermState<T> {
         let threshold = self.target.threshold();
 
         *self.value_at_scan() =
-            HeapCellValue::Addr(Addr::PStrLocation(threshold, 0));
+            HeapCellValue::Addr(Addr::PStrLocation(threshold, n));
 
         self.scan += 1;
 
         let (pstr, has_tail) =
             match &self.target[addr] {
                 &HeapCellValue::PartialString(ref pstr, has_tail) => {
-                    (pstr.clone_from_offset(n), has_tail)
+                    (pstr.clone_from_offset(0), has_tail)
                 }
                 _ => {
                     unreachable!()
@@ -130,7 +130,7 @@ impl<T: CopierTarget> CopyTermState<T> {
 
         self.target.push(HeapCellValue::PartialString(pstr, has_tail));
 
-        let replacement = HeapCellValue::Addr(Addr::PStrLocation(threshold, 0));
+        let replacement = HeapCellValue::Addr(Addr::PStrLocation(threshold, n));
 
         let trail_item = mem::replace(
             &mut self.target[addr],

src/machine/dynamic_database.rs

@@ -1,10 +1,10 @@
-use prolog_parser::ast::*;
+use crate::prolog_parser::ast::*;
 
-use crate::prolog::heap_print::*;
-use crate::prolog::machine::*;
-use crate::prolog::machine::compile::*;
-use crate::prolog::machine::machine_errors::*;
-use crate::prolog::machine::streams::*;
+use crate::heap_print::*;
+use crate::machine::*;
+use crate::machine::compile::*;
+use crate::machine::machine_errors::*;
+use crate::machine::streams::*;
 
 use std::convert::TryFrom;
 
@@ -66,6 +66,9 @@ impl Machine {
                     }
                 }
             }
+            Addr::Fixnum(arity) => {
+                usize::try_from(arity).unwrap()
+            }
             Addr::Usize(n) => {
                 n
             }
@@ -98,6 +101,18 @@ impl Machine {
     }
 
     fn make_undefined(&mut self, name: ClauseName, arity: usize) {
+        let module_name = name.owning_module();
+
+        match self.indices.modules.get(&module_name) {
+            Some(ref module) => {
+                if let Some(idx) = module.code_dir.get(&(name.clone(), arity)) {
+                    set_code_index!(idx, IndexPtr::DynamicUndefined, module_name);
+                }
+            }
+            None => {
+            }
+        }
+
         if let Some(idx) = self.indices.code_dir.get(&(name, arity)) {
             set_code_index!(idx, IndexPtr::DynamicUndefined, clause_name!("user"));
         }
@@ -258,7 +273,12 @@ impl Machine {
                         unreachable!()
                     }
                 }
-            _ => unreachable!(),
+            Addr::Fixnum(arity) => {
+                usize::try_from(arity).unwrap()
+            }
+            _ => {
+                unreachable!()
+            }
         };
 
         let (mut name, arity) = self.get_predicate_key(temp_v!(1), temp_v!(2));

src/machine/heap.rs

@@ -2,9 +2,9 @@ use core::marker::PhantomData;
 
 use crate::prolog_parser::ast::Constant;
 
-use crate::prolog::machine::machine_indices::*;
-use crate::prolog::machine::partial_string::*;
-use crate::prolog::machine::raw_block::*;
+use crate::machine::machine_indices::*;
+use crate::machine::partial_string::*;
+use crate::machine::raw_block::*;
 
 use std::convert::TryFrom;
 use std::mem;

src/machine/machine_errors.rs

@@ -1,10 +1,10 @@
-use prolog_parser::ast::*;
+use crate::prolog_parser::ast::*;
 
-use crate::prolog::forms::{ModuleSource, Number, PredicateKey};
-use crate::prolog::machine::heap::*;
-use crate::prolog::machine::machine_indices::*;
-use crate::prolog::machine::machine_state::*;
-use crate::prolog::rug::Integer;
+use crate::forms::{ModuleSource, Number, PredicateKey};
+use crate::machine::heap::*;
+use crate::machine::machine_indices::*;
+use crate::machine::machine_state::*;
+use crate::rug::Integer;
 
 use std::rc::Rc;
 
@@ -43,6 +43,21 @@ impl TypeError for Addr {
     }
 }
 
+impl TypeError for HeapCellValue {
+    fn type_error(self, _: usize, valid_type: ValidType) -> MachineError {
+        let stub = functor!(
+            "type_error",
+            [atom(valid_type.as_str()), value(self)]
+        );
+
+        MachineError {
+            stub,
+            location: None,
+            from: ErrorProvenance::Received
+        }
+    }
+}
+
 impl TypeError for MachineStub {
     fn type_error(self, h: usize, valid_type: ValidType) -> MachineError {
         let stub = functor!(
@@ -502,7 +517,7 @@ pub enum ValidType {
     InCharacter,
     Integer,
     List,
-    //    Number,
+    Number,
     Pair,
     //    PredicateIndicator,
     //    Variable
@@ -525,7 +540,7 @@ impl ValidType {
             ValidType::InCharacter => "in_character",
             ValidType::Integer => "integer",
             ValidType::List => "list",
-            //            ValidType::Number => "number",
+            ValidType::Number => "number",
             ValidType::Pair => "pair",
             //            ValidType::PredicateIndicator => "predicate_indicator",
             //            ValidType::Variable => "variable"
@@ -560,7 +575,7 @@ impl DomainErrorType {
 // from 7.12.2 f) of 13211-1:1995
 #[derive(Debug, Clone, Copy)]
 pub enum RepFlag {
-    //    Character,
+    Character,
     CharacterCode,
     InCharacterCode,
     MaxArity,
@@ -571,7 +586,7 @@ pub enum RepFlag {
 impl RepFlag {
     pub fn as_str(self) -> &'static str {
         match self {
-            //            RepFlag::Character => "character",
+            RepFlag::Character => "character",
             RepFlag::CharacterCode => "character_code",
             RepFlag::InCharacterCode => "in_character_code",
             RepFlag::MaxArity => "max_arity",
@@ -825,5 +840,4 @@ impl From<ParserError> for EvalSession {
     fn from(err: ParserError) -> Self {
         EvalSession::from(SessionError::ParserError(err))
     }
-
 }

src/machine/machine_indices.rs

@@ -1,21 +1,21 @@
-use prolog_parser::ast::*;
-use prolog_parser::tabled_rc::*;
+use crate::prolog_parser::ast::*;
+use crate::prolog_parser::tabled_rc::*;
 
-use crate::prolog::clause_types::*;
-use crate::prolog::fixtures::*;
-use crate::prolog::forms::*;
-use crate::prolog::machine::code_repo::CodeRepo;
-use crate::prolog::machine::Ball;
-use crate::prolog::machine::heap::*;
-use crate::prolog::machine::machine_state::*;
-use crate::prolog::machine::partial_string::*;
-use crate::prolog::machine::raw_block::RawBlockTraits;
-use crate::prolog::machine::streams::Stream;
-use crate::prolog::instructions::*;
-use crate::prolog::ordered_float::OrderedFloat;
-use crate::prolog::rug::{Integer, Rational};
+use crate::clause_types::*;
+use crate::fixtures::*;
+use crate::forms::*;
+use crate::machine::code_repo::CodeRepo;
+use crate::machine::Ball;
+use crate::machine::heap::*;
+use crate::machine::machine_state::*;
+use crate::machine::partial_string::*;
+use crate::machine::raw_block::RawBlockTraits;
+use crate::machine::streams::Stream;
+use crate::instructions::*;
+use crate::ordered_float::OrderedFloat;
+use crate::rug::{Integer, Rational};
 
-use indexmap::IndexMap;
+use crate::indexmap::IndexMap;
 
 use std::cell::RefCell;
 use std::cmp::Ordering;
@@ -118,7 +118,7 @@ impl PartialEq<Ref> for Addr {
     }
 }
 
-// for use in MachineState::bind.
+// for use crate::in MachineState::bind.
 impl PartialOrd<Ref> for Addr {
     fn partial_cmp(&self, r: &Ref) -> Option<Ordering> {
         match self {
@@ -272,19 +272,6 @@ impl Addr {
             &Addr::Float(f) => {
                 Some(Constant::Float(f))
             }
-            &Addr::PStrLocation(h, n) => {
-                let mut heap_pstr_iter =
-                    machine_st.heap_pstr_iter(Addr::PStrLocation(h, n));
-
-                let buf = heap_pstr_iter.to_string();
-                let end_addr = heap_pstr_iter.focus();
-
-                if end_addr == Addr::EmptyList {
-                    Some(Constant::String(Rc::new(buf)))
-                } else {
-                    None
-                }
-            }
             &Addr::Usize(n) => {
                 Some(Constant::Usize(n))
             }

src/machine/machine_state.rs

@@ -1,22 +1,22 @@
-use prolog_parser::ast::*;
-use prolog_parser::tabled_rc::*;
+use crate::prolog_parser::ast::*;
+use crate::prolog_parser::tabled_rc::*;
 
-use crate::prolog::clause_types::*;
-use crate::prolog::forms::*;
-use crate::prolog::heap_print::*;
-use crate::prolog::machine::attributed_variables::*;
-use crate::prolog::machine::copier::*;
-use crate::prolog::machine::heap::*;
-use crate::prolog::machine::machine_errors::*;
-use crate::prolog::machine::machine_indices::*;
-use crate::prolog::machine::modules::*;
-use crate::prolog::machine::stack::*;
-use crate::prolog::machine::streams::*;
-use crate::prolog::rug::Integer;
+use crate::clause_types::*;
+use crate::forms::*;
+use crate::heap_print::*;
+use crate::machine::attributed_variables::*;
+use crate::machine::copier::*;
+use crate::machine::heap::*;
+use crate::machine::machine_errors::*;
+use crate::machine::machine_indices::*;
+use crate::machine::modules::*;
+use crate::machine::stack::*;
+use crate::machine::streams::*;
+use crate::rug::Integer;
 
-use downcast::Any;
+use crate::downcast::Any;
 
-use indexmap::{IndexMap, IndexSet};
+use crate::indexmap::{IndexMap, IndexSet};
 
 use std::cmp::Ordering;
 use std::convert::TryFrom;
@@ -636,11 +636,10 @@ impl MachineState {
         }
 
         let mut orig_stream = stream.clone();
-        let mut stream = self.open_parsing_stream(stream, "read_term", 3)?;
 
         loop {
             match self.read(
-                &mut stream,
+                stream.clone(),
                 indices.atom_tbl.clone(),
                 &indices.op_dir,
             ) {
@@ -1337,14 +1336,8 @@ pub(crate) trait CallPolicy: Any + fmt::Debug {
                 return_from_clause!(machine_st.last_call, machine_st)
             }
             &BuiltInClauseType::Read => {
-                let mut stream = machine_st.open_parsing_stream(
-                    current_input_stream.clone(),
-                    "read",
-                    1,
-                )?;
-
                 match machine_st.read(
-                    &mut stream,
+                    current_input_stream.clone(),
                     indices.atom_tbl.clone(),
                     &indices.op_dir,
                 ) {

src/machine/machine_state_impl.rs

@@ -1,24 +1,24 @@
-use prolog_parser::ast::*;
-use prolog_parser::tabled_rc::*;
+use crate::prolog_parser::ast::*;
+use crate::prolog_parser::tabled_rc::*;
 
-use crate::prolog::clause_types::*;
-use crate::prolog::forms::*;
-use crate::prolog::heap_iter::*;
-use crate::prolog::instructions::*;
-use crate::prolog::machine::INTERRUPT;
-use crate::prolog::machine::attributed_variables::*;
-use crate::prolog::machine::code_repo::CodeRepo;
-use crate::prolog::machine::copier::*;
-use crate::prolog::machine::heap::*;
-use crate::prolog::machine::machine_errors::*;
-use crate::prolog::machine::machine_indices::*;
-use crate::prolog::machine::machine_state::*;
-use crate::prolog::machine::stack::*;
-use crate::prolog::machine::streams::*;
-use crate::prolog::ordered_float::*;
-use crate::prolog::rug::Integer;
+use crate::clause_types::*;
+use crate::forms::*;
+use crate::heap_iter::*;
+use crate::instructions::*;
+use crate::machine::INTERRUPT;
+use crate::machine::attributed_variables::*;
+use crate::machine::code_repo::CodeRepo;
+use crate::machine::copier::*;
+use crate::machine::heap::*;
+use crate::machine::machine_errors::*;
+use crate::machine::machine_indices::*;
+use crate::machine::machine_state::*;
+use crate::machine::stack::*;
+use crate::machine::streams::*;
+use crate::ordered_float::*;
+use crate::rug::Integer;
 
-use indexmap::{IndexMap, IndexSet};
+use crate::indexmap::{IndexMap, IndexSet};
 
 use std::cmp::Ordering;
 use std::convert::TryFrom;
@@ -689,7 +689,7 @@ impl MachineState {
             &mut HeapPtr::PStrChar(h, ref mut n) |
             &mut HeapPtr::PStrLocation(h, ref mut n) => {
                 match &self.heap[h] {
-                    HeapCellValue::PartialString(ref pstr, _) => {
+                    &HeapCellValue::PartialString(ref pstr, _) => {
                         for c in pstr.range_from(*n ..).take(rhs) {
                             *n += c.len_utf8();
                         }
@@ -697,7 +697,6 @@ impl MachineState {
                         self.s = HeapPtr::PStrLocation(h, *n);
                     }
                     _ => {
-                        unreachable!()
                     }
                 }
             }
@@ -819,7 +818,7 @@ impl MachineState {
 
                         self.bind(addr.as_var().unwrap(), pstr_addr);
                     }
-                    Addr::Lis(l) if !self.flags.double_quotes.is_atom() => {
+                    Addr::Lis(l) => {
                         let h = self.heap.h();
 
                         let pstr_addr =
@@ -921,7 +920,7 @@ impl MachineState {
                     self.fail = true;
                 }
             }
-            Addr::Lis(l) if !self.flags.double_quotes.is_atom() => {
+            Addr::Lis(l) => {
                 let addr = self.heap.put_constant(c.clone());
                 self.unify(Addr::Lis(l), addr);
             }
@@ -953,7 +952,7 @@ impl MachineState {
 
     pub(super)
     fn execute_arith_instr(&mut self, instr: &ArithmeticInstruction) {
-        let stub = MachineError::functor_stub(clause_name!("(is)"), 2);
+        let stub = MachineError::functor_stub(clause_name!("is"), 2);
 
         match instr {
             &ArithmeticInstruction::Add(ref a1, ref a2, t) => {
@@ -1405,11 +1404,7 @@ impl MachineState {
                         v
                     }
                     Addr::PStrLocation(..) => {
-                        if !self.flags.double_quotes.is_atom() {
-                            l
-                        } else {
-                            c
-                        }
+                        l
                     }
                     Addr::Char(_) | Addr::Con(_) | Addr::CutPoint(_) |
                     Addr::EmptyList | Addr::Fixnum(_) | Addr::Float(_) | Addr::Usize(_) => {
@@ -1885,11 +1880,10 @@ impl MachineState {
                         unreachable!()
                     }
                 }
-                (Addr::PStrLocation(..), Addr::Lis(_))
-              | (Addr::Lis(_), Addr::PStrLocation(..))
-                    if !self.flags.double_quotes.is_atom() => {
-                        continue;
-                    }
+                (Addr::PStrLocation(..), Addr::Lis(_)) |
+                (Addr::Lis(_), Addr::PStrLocation(..)) => {
+                    continue;
+                }
                 (pstr1 @ Addr::PStrLocation(..), pstr2 @ Addr::PStrLocation(..)) => {
                     let mut i1 = self.heap_pstr_iter(pstr1);
                     let mut i2 = self.heap_pstr_iter(pstr2);
@@ -2249,7 +2243,7 @@ impl MachineState {
                         (
                             Addr::PStrLocation(..),
                             Addr::Lis(_),
-                        ) if !self.flags.double_quotes.is_atom() => {
+                        ) => {
                         }
                         (
                             Addr::Lis(_),
@@ -2278,7 +2272,7 @@ impl MachineState {
                         (
                             Addr::PStrLocation(..),
                             Addr::Str(s),
-                        ) if !self.flags.double_quotes.is_atom() => {
+                        ) => {
                             if let &HeapCellValue::NamedStr(a1, ref n1, _) = &self.heap[s] {
                                 if a1 != 2 || n1.as_str() != "." {
                                     return Some(a1.cmp(&2).then_with(|| n1.as_str().cmp(".")));
@@ -2290,7 +2284,7 @@ impl MachineState {
                         (
                             Addr::Str(s),
                             Addr::PStrLocation(..),
-                        ) if !self.flags.double_quotes.is_atom() => {
+                        ) => {
                             if let &HeapCellValue::NamedStr(a1, ref n1, _) = &self.heap[s] {
                                 if a1 != 2 || n1.as_str() != "." {
                                     return Some(2.cmp(&a1).then_with(|| ".".cmp(n1.as_str())));
@@ -2376,14 +2370,7 @@ impl MachineState {
                         }
                     }
                     _ => {
-                        match d {
-                            Addr::Char(_) if self.flags.double_quotes.is_codes() => {
-                                self.p += 1;
-                            }
-                            _ => {
-                                self.fail = true;
-                            }
-                        }
+                        self.fail = true;
                     }
                 }
             }
@@ -2474,22 +2461,29 @@ impl MachineState {
     fn try_functor_fabricate_struct(
         &mut self,
         name: ClauseName,
-        arity: isize,
+        arity: usize,
         spec: Option<SharedOpDesc>,
         op_dir: &OpDir,
         r: Ref,
     ) {
-        let spec = fetch_atom_op_spec(name.clone(), spec, op_dir);
+        let spec = spec.and_then(|spec| {
+            if spec.arity() != arity {
+                fetch_op_spec(name.clone(), arity, op_dir)
+            } else {
+                Some(spec)
+            }
+        });
 
         let f_a = if name.as_str() == "." && arity == 2 {
             Addr::Lis(self.heap.h())
         } else {
-            self.heap.to_unifiable(HeapCellValue::NamedStr(arity as usize, name, spec))
+            self.heap.to_unifiable(HeapCellValue::NamedStr(arity, name, spec))
         };
 
-        for _ in 0..arity {
-            let h = self.heap.h();
-            self.heap.push(HeapCellValue::Addr(Addr::HeapCell(h)));
+        let h = self.heap.h();
+
+        for i in 0 .. arity {
+            self.heap.push(HeapCellValue::Addr(Addr::HeapCell(h + i)));
         }
 
         self.bind(r, f_a);
@@ -2510,7 +2504,13 @@ impl MachineState {
             }
             Addr::Str(o) => match self.heap.clone(o) {
                 HeapCellValue::NamedStr(arity, name, spec) => {
-                    let spec = fetch_op_spec(name.clone(), arity, spec, &indices.op_dir);
+                    let spec = fetch_op_spec_from_existing(
+                        name.clone(),
+                        arity,
+                        spec,
+                        &indices.op_dir,
+                    );
+
                     self.try_functor_compound_case(name, arity, spec)
                 }
                 _ => {
@@ -2518,7 +2518,13 @@ impl MachineState {
                 }
             },
             Addr::Lis(_) | Addr::PStrLocation(..) => {
-                let spec = fetch_op_spec(clause_name!("."), 2, None, &indices.op_dir);
+                let spec = fetch_op_spec_from_existing(
+                    clause_name!("."),
+                    2,
+                    None,
+                    &indices.op_dir,
+                );
+
                 self.try_functor_compound_case(clause_name!("."), 2, spec)
             }
             Addr::AttrVar(..) | Addr::HeapCell(_) | Addr::StackCell(..) => {
@@ -2589,7 +2595,7 @@ impl MachineState {
                         if let HeapCellValue::Atom(name, spec) = self.heap.clone(h) {
                             self.try_functor_fabricate_struct(
                                 name,
-                                arity,
+                                arity as usize,
                                 spec,
                                 &indices.op_dir,
                                 a1.as_var().unwrap(),
@@ -2609,7 +2615,7 @@ impl MachineState {
                     Addr::Char(c) => {
                         self.try_functor_fabricate_struct(
                             clause_name!(c.to_string(), indices.atom_tbl),
-                            arity,
+                            arity as usize,
                             None,
                             &indices.op_dir,
                             a1.as_var().unwrap(),
@@ -2889,7 +2895,7 @@ impl MachineState {
                 | (
                     HeapCellValue::Addr(Addr::PStrLocation(..)),
                     HeapCellValue::Addr(Addr::Lis(_)),
-                ) if !self.flags.double_quotes.is_atom() => {
+                ) => {
                 }
                 (
                     HeapCellValue::NamedStr(ar1, n1, _),

src/machine/mod.rs

@@ -1,12 +1,12 @@
-use prolog_parser::ast::*;
-use prolog_parser::tabled_rc::*;
+use crate::prolog_parser::ast::*;
+use crate::prolog_parser::tabled_rc::*;
 
-use crate::prolog::clause_types::*;
-use crate::prolog::forms::*;
-use crate::prolog::heap_print::*;
-use crate::prolog::instructions::*;
-use crate::prolog::machine::heap::*;
-use crate::prolog::read::*;
+use crate::clause_types::*;
+use crate::forms::*;
+use crate::heap_print::*;
+use crate::instructions::*;
+use crate::machine::heap::*;
+use crate::read::*;
 
 mod attributed_variables;
 pub(super) mod code_repo;
@@ -32,17 +32,17 @@ mod arithmetic_ops;
 mod machine_state_impl;
 mod system_calls;
 
-use crate::prolog::machine::attributed_variables::*;
-use crate::prolog::machine::code_repo::*;
-use crate::prolog::machine::compile::*;
-use crate::prolog::machine::machine_errors::*;
-use crate::prolog::machine::machine_indices::*;
-use crate::prolog::machine::machine_state::*;
-use crate::prolog::machine::modules::*;
-use crate::prolog::machine::streams::*;
-use crate::prolog::machine::toplevel::*;
+use crate::machine::attributed_variables::*;
+use crate::machine::code_repo::*;
+use crate::machine::compile::*;
+use crate::machine::machine_errors::*;
+use crate::machine::machine_indices::*;
+use crate::machine::machine_state::*;
+use crate::machine::modules::*;
+use crate::machine::streams::*;
+use crate::machine::toplevel::*;
 
-use indexmap::IndexMap;
+use crate::indexmap::IndexMap;
 
 use std::collections::VecDeque;
 use std::convert::TryFrom;
@@ -212,17 +212,6 @@ impl SubModuleUser for IndexStore {
     }
 }
 
-#[inline]
-fn current_dir() -> std::path::PathBuf {
-    let mut path_buf = std::path::PathBuf::from(PROJECT_DIR);
-
-    // file!() always produces a path relative to PROJECT_DIR.
-    path_buf = path_buf.join(std::path::PathBuf::from(file!()));
-
-    path_buf.pop();
-    path_buf
-}
-
 include!(concat!(env!("OUT_DIR"), "/libraries.rs"));
 
 static TOPLEVEL: &str = include_str!("../toplevel.pl");
@@ -230,12 +219,7 @@ static TOPLEVEL: &str = include_str!("../toplevel.pl");
 impl Machine {
     fn compile_special_forms(&mut self)
     {
-        let current_dir = current_dir();
-
-        let verify_attrs_src = ListingSource::from_file_and_path(
-            clause_name!("attributed_variables.pl"),
-            current_dir.clone(),
-        );
+        let verify_attrs_src = ListingSource::User;
 
         match compile_special_form(
             self,
@@ -250,10 +234,7 @@ impl Machine {
                 panic!("Machine::compile_special_forms() failed at VERIFY_ATTRS"),
         }
 
-        let project_attrs_src = ListingSource::from_file_and_path(
-            clause_name!("project_attributes.pl"),
-            current_dir,
-        );
+        let project_attrs_src = ListingSource::User;
 
         match compile_special_form(
             self,
@@ -273,13 +254,7 @@ impl Machine {
     {
         self.toplevel_idx = self.code_repo.code.len();
 
-        let mut current_dir = current_dir();
-        current_dir.pop();
-
-        let top_lvl_src = ListingSource::from_file_and_path(
-            clause_name!("toplevel.pl"),
-            current_dir,
-        );
+        let top_lvl_src = ListingSource::User;
 
         compile_user_module(
             self,
@@ -371,6 +346,8 @@ impl Machine {
 
     pub fn new(current_input_stream: Stream, current_output_stream: Stream) -> Self
     {
+        use crate::ref_thread_local::RefThreadLocal;
+
         let mut wam = Machine {
             machine_st: MachineState::new(),
             inner_heap: Heap::new(),
@@ -383,78 +360,59 @@ impl Machine {
         };
 
         let atom_tbl = wam.indices.atom_tbl.clone();
-        let mut lib_path = current_dir();
-
-        lib_path.pop();
-        lib_path.push("lib");
 
         wam.indices.add_term_and_goal_expansion_indices();
 
         compile_listing(
             &mut wam,
-            Stream::from(BUILTINS),
+            Stream::from(LIBRARIES.borrow()["builtins"]),
             default_index_store!(atom_tbl.clone()),
             true,
-            ListingSource::from_file_and_path(
-                clause_name!("builtins.pl"),
-                lib_path.clone(),
-            ),
+            ListingSource::User,
         );
 
         wam.compile_special_forms();
 
-        compile_user_module(&mut wam,
-                            Stream::from(ERROR),
-                            true,
-                            ListingSource::from_file_and_path(
-                                clause_name!("error"),
-                                lib_path.clone(),
-                            )
+        compile_user_module(
+            &mut wam,
+            Stream::from(LIBRARIES.borrow()["error"]),
+            true,
+            ListingSource::User,
         );
 
-        compile_user_module(&mut wam,
-                            Stream::from(PAIRS),
-                            true,
-                            ListingSource::from_file_and_path(
-                                clause_name!("pairs"),
-                                lib_path.clone(),
-                            )
+        compile_user_module(
+            &mut wam,
+            Stream::from(LIBRARIES.borrow()["pairs"]),
+            true,
+            ListingSource::User,
         );
 
-        compile_user_module(&mut wam,
-                            Stream::from(LISTS),
-                            true,
-                            ListingSource::from_file_and_path(
-                                clause_name!("lists"),
-                                lib_path.clone(),
-                            ),
+        compile_user_module(
+            &mut wam,
+            Stream::from(LIBRARIES.borrow()["lists"]),
+            true,
+            ListingSource::User,
         );
 
-        compile_user_module(&mut wam,
-                            Stream::from(ISO_EXT),
-                            true,
-                            ListingSource::from_file_and_path(
-                                clause_name!("iso_ext"),
-                                lib_path.clone(),
-                            )
+        compile_user_module(
+            &mut wam,
+            Stream::from(LIBRARIES.borrow()["iso_ext"]),
+            true,
+            ListingSource::User,
         );
 
-        compile_user_module(&mut wam,
-                            Stream::from(SI),
-                            true,
-                            ListingSource::from_file_and_path(
-                                clause_name!("si"),
-                                lib_path.clone(),
-                            )
+        compile_user_module(
+            &mut wam,
+            Stream::from(LIBRARIES.borrow()["si"]),
+            true,
+            ListingSource::User,
         );
 
-        compile_user_module(&mut wam,
-                            Stream::from(CHARSIO),
-                            true,
-                            ListingSource::from_file_and_path(
-                                clause_name!("si"),
-                                lib_path.clone(),
-                            )
+        compile_user_module(
+            &mut wam,
+            Stream::from(LIBRARIES.borrow()["charsio"]),
+            true,
+            ListingSource::User,
         );
 
         if wam.compile_top_level().is_err() {
@@ -681,8 +639,15 @@ impl Machine {
                     name.clone(),
                 HeapCellValue::Addr(Addr::Char(c)) =>
                     clause_name!(c.to_string(), self.indices.atom_tbl),
-	            _ =>
-                    unreachable!(),
+                HeapCellValue::Addr(addr @ Addr::PStrLocation(..)) => {
+                    let mut heap_pstr_iter =
+                        self.machine_st.heap_pstr_iter(*addr);
+                    clause_name!(
+                        heap_pstr_iter.to_string(),
+                        self.indices.atom_tbl
+                    )
+                }
+                _ => unreachable!(),
             }
 	    };
 

src/machine/modules.rs

@@ -1,10 +1,10 @@
-use prolog_parser::ast::*;
-use prolog_parser::tabled_rc::*;
+use crate::prolog_parser::ast::*;
+use crate::prolog_parser::tabled_rc::*;
 
-use crate::prolog::forms::*;
-use crate::prolog::machine::code_repo::*;
-use crate::prolog::machine::machine_errors::*;
-use crate::prolog::machine::machine_indices::*;
+use crate::forms::*;
+use crate::machine::code_repo::*;
+use crate::machine::machine_errors::*;
+use crate::machine::machine_indices::*;
 
 use std::collections::VecDeque;
 use std::mem;

src/machine/stack.rs

@@ -1,8 +1,8 @@
-use crate::prolog::machine::machine_indices::*;
-use crate::prolog::machine::raw_block::*;
-
 use core::marker::PhantomData;
 
+use crate::machine::machine_indices::*;
+use crate::machine::raw_block::*;
+
 use std::mem;
 use std::ops::{Index, IndexMut};
 use std::ptr;

src/machine/streams.rs

@@ -1,22 +1,26 @@
 use crate::prolog_parser::ast::*;
 
-use crate::prolog::read::PrologStream;
-use crate::prolog::read::readline::*;
-use crate::prolog::machine::machine_errors::*;
-use crate::prolog::machine::machine_indices::*;
-use crate::prolog::machine::machine_state::*;
+use crate::read::PrologStream;
+use crate::read::readline::*;
+use crate::machine::machine_errors::*;
+use crate::machine::machine_indices::*;
+use crate::machine::machine_state::*;
 
-use std::cmp::Ordering;
+use std::cmp::{min, Ordering};
 use std::cell::RefCell;
 use std::error::Error;
 use std::fmt;
 use std::fs::File;
+use std::io;
 use std::io::{stdout, Cursor, ErrorKind, Read, Seek, SeekFrom, Write};
 use std::hash::{Hash, Hasher};
+use std::mem;
 use std::net::{Shutdown, TcpStream};
 use std::ops::DerefMut;
 use std::rc::Rc;
 
+use crate::native_tls::TlsStream;
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub enum StreamType {
     Binary,
@@ -90,17 +94,81 @@ impl EOFAction {
     }
 }
 
+fn parser_top_to_bytes(mut buf: Vec<io::Result<char>>) -> io::Result<Vec<u8>> {
+    let mut str_buf = String::new();
+
+    while let Some(c) = buf.pop() {
+        str_buf.push(c?);
+    }
+
+    unsafe {
+        let array = str_buf.as_bytes_mut();
+        array.reverse();
+        Ok(Vec::from(array))
+    }
+}
+
 /* all these streams are closed automatically when the instance is
  * dropped. */
 pub enum StreamInstance {
     Bytes(Cursor<Vec<u8>>),
-    DynReadSource(Box<dyn Read>),
     InputFile(ClauseName, File),
     OutputFile(ClauseName, File, bool), // File, append.
     Null,
+    PausedPrologStream(Vec<u8>, Box<StreamInstance>),
     ReadlineStream(ReadlineStream),
+    StaticStr(Cursor<&'static str>),
     Stdout,
     TcpStream(ClauseName, TcpStream),
+    TlsStream(ClauseName, TlsStream<TcpStream>)
+}
+
+impl StreamInstance {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        match self {
+            StreamInstance::PausedPrologStream(ref mut put_back, ref mut stream) => {
+                let mut index = 0;
+
+                while index < min(buf.len(), put_back.len()) {
+                    let b = put_back.pop().unwrap();
+                    buf[index] = b;
+                    index += 1;
+                }
+
+                if index == buf.len() {
+                    Ok(buf.len())
+                } else {
+                    stream.read(&mut buf[index ..])
+                }
+            }
+            StreamInstance::InputFile(_, ref mut file) => {
+                file.read(buf)
+            }
+            StreamInstance::TcpStream(_, ref mut tcp_stream) => {
+                tcp_stream.read(buf)
+            }
+            StreamInstance::TlsStream(_, ref mut tls_stream) => {
+                tls_stream.read(buf)
+            }
+            StreamInstance::ReadlineStream(ref mut rl_stream) => {
+                rl_stream.read(buf)
+            }
+            StreamInstance::StaticStr(ref mut src) => {
+                src.read(buf)
+            }
+            StreamInstance::Bytes(ref mut cursor) => {
+                cursor.read(buf)
+            }
+            StreamInstance::OutputFile(..) |
+            StreamInstance::Stdout |
+            StreamInstance::Null => {
+                Err(std::io::Error::new(
+                    ErrorKind::PermissionDenied,
+                    StreamError::ReadFromOutputStream,
+                ))
+            }
+        }
+    }
 }
 
 impl Drop for StreamInstance {
@@ -109,6 +177,9 @@ impl Drop for StreamInstance {
             StreamInstance::TcpStream(_, ref mut tcp_stream) => {
                 discard_result!(tcp_stream.shutdown(Shutdown::Both));
             }
+            StreamInstance::TlsStream(_, ref mut tls_stream) => {
+                discard_result!(tls_stream.shutdown());
+            }
             _ => {
             }
         }
@@ -120,17 +191,24 @@ impl fmt::Debug for StreamInstance {
         match self {
             &StreamInstance::Bytes(ref bytes) =>
                 write!(fmt, "Bytes({:?})", bytes),
-            &StreamInstance::DynReadSource(_) =>
-                write!(fmt, "DynReadSource(_)"),  // Hacky solution.
-            &StreamInstance::InputFile(_, ref file) => write!(fmt, "InputFile({:?})", file),
-            &StreamInstance::OutputFile(_, ref file, _) => write!(fmt, "OutputFile({:?})", file),
-            &StreamInstance::Null => write!(fmt, "Null"),
+            &StreamInstance::StaticStr(_) =>
+                write!(fmt, "StaticStr(_)"),  // Hacky solution.
+            &StreamInstance::InputFile(_, ref file) =>
+                write!(fmt, "InputFile({:?})", file),
+            &StreamInstance::OutputFile(_, ref file, _) =>
+                write!(fmt, "OutputFile({:?})", file),
+            &StreamInstance::Null =>
+                write!(fmt, "Null"),
+            &StreamInstance::PausedPrologStream(ref put_back, ref stream) =>
+                write!(fmt, "PausedPrologStream({:?}, {:?})", put_back, stream),
             &StreamInstance::ReadlineStream(ref readline_stream) =>
                 write!(fmt, "ReadlineStream({:?})", readline_stream),
-            // &StreamInstance::Stdin => write!(fmt, "Stdin"),
-            &StreamInstance::Stdout => write!(fmt, "Stdout"),
+            &StreamInstance::Stdout =>
+                write!(fmt, "Stdout"),
             &StreamInstance::TcpStream(_, ref tcp_stream) =>
                 write!(fmt, "TcpStream({:?})", tcp_stream),
+            &StreamInstance::TlsStream(_, ref tls_stream) =>
+                write!(fmt, "TlsStream({:?})", tls_stream),
         }
     }
 }
@@ -274,7 +352,7 @@ impl From<ReadlineStream> for Stream {
 
 impl From<&'static str> for Stream {
     fn from(src: &'static str) -> Stream {
-        Stream::from_inst(StreamInstance::DynReadSource(Box::new(src.as_bytes())))
+        Stream::from_inst(StreamInstance::StaticStr(Cursor::new(src)))
     }
 }
 
@@ -405,12 +483,14 @@ impl Stream {
     fn mode(&self) -> &'static str {
         match self.stream_inst.0.borrow().1 {
             StreamInstance::Bytes(_) |
+            StreamInstance::PausedPrologStream(..) |
             StreamInstance::ReadlineStream(_) |
-            StreamInstance::DynReadSource(_) |
+            StreamInstance::StaticStr(_) |
             StreamInstance::InputFile(..) => {
                 "read"
             }
-            StreamInstance::TcpStream(..) => {
+            StreamInstance::TcpStream(..) |
+            StreamInstance::TlsStream(..) => {
                 "read_append"
             }
             StreamInstance::OutputFile(_, _, true) => {
@@ -449,6 +529,12 @@ impl Stream {
         Stream::from_inst(StreamInstance::TcpStream(address, tcp_stream))
     }
 
+    #[inline]
+    pub(crate)
+    fn from_tls_stream(address: ClauseName, tls_stream: TlsStream<TcpStream>) -> Self {
+        Stream::from_inst(StreamInstance::TlsStream(address, tls_stream))
+    }
+
     #[inline]
     pub(crate)
     fn from_file_as_output(name: ClauseName, file: File, in_append_mode: bool) -> Self {
@@ -478,7 +564,6 @@ impl Stream {
     pub(crate)
     fn is_stdin(&self) -> bool {
         match self.stream_inst.0.borrow().1 {
-            //StreamInstance::Stdin |
             StreamInstance::ReadlineStream(_) => {
                 true
             }
@@ -508,11 +593,12 @@ impl Stream {
     pub(crate)
     fn is_input_stream(&self) -> bool {
         match self.stream_inst.0.borrow().1 {
-            // StreamInstance::Stdin |
             StreamInstance::TcpStream(..) |
+            StreamInstance::TlsStream(..) |
             StreamInstance::Bytes(_) |
+            StreamInstance::PausedPrologStream(..) |
             StreamInstance::ReadlineStream(_) |
-            StreamInstance::DynReadSource(_) |
+            StreamInstance::StaticStr(_) |
             StreamInstance::InputFile(..) => {
                 true
             }
@@ -528,6 +614,7 @@ impl Stream {
         match self.stream_inst.0.borrow().1 {
             StreamInstance::Stdout
           | StreamInstance::TcpStream(..)
+          | StreamInstance::TlsStream(..)
           | StreamInstance::Bytes(_)
           | StreamInstance::OutputFile(..) => {
                 true
@@ -538,27 +625,49 @@ impl Stream {
         }
     }
 
+    fn unpause_stream(&mut self) {
+        let stream_inst =
+            match self.stream_inst.0.borrow_mut().1 {
+                StreamInstance::PausedPrologStream(ref put_back, ref mut stream_inst)
+                    if put_back.is_empty() => {
+                        mem::replace(&mut **stream_inst, StreamInstance::Null)
+                    }
+                _ => {
+                    return;
+                }
+            };
+
+        self.stream_inst.0.borrow_mut().1 = stream_inst;
+    }
+
     // returns true on success.
     #[inline]
     pub(super)
     fn reset(&mut self) -> bool {
         self.stream_inst.0.borrow_mut().0 = false;
 
-        match self.stream_inst.0.borrow_mut().1 {
-            StreamInstance::Bytes(ref mut cursor) => {
-                cursor.set_position(0);
-                true
-            }
-            StreamInstance::InputFile(_, ref mut file) => {
-                file.seek(SeekFrom::Start(0)).unwrap();
-                true
-            }
-            StreamInstance::ReadlineStream(_) => {
-                true
-            }
-            _ => {
-                false
+        loop {
+            match self.stream_inst.0.borrow_mut().1 {
+                StreamInstance::Bytes(ref mut cursor) => {
+                    cursor.set_position(0);
+                    return true;
+                }
+                StreamInstance::InputFile(_, ref mut file) => {
+                    file.seek(SeekFrom::Start(0)).unwrap();
+                    return true;
+                }
+                StreamInstance::PausedPrologStream(ref mut put_back, _) => {
+                    put_back.clear();
+                }
+                StreamInstance::ReadlineStream(_) => {
+                    return true;
+                }
+                _ => {
+                    return false;
+                }
             }
+
+            self.unpause_stream();
         }
     }
 
@@ -619,7 +728,7 @@ impl Stream {
     #[inline]
     pub(crate)
     fn peek_char(&mut self) -> std::io::Result<char> {
-        use unicode_reader::CodePoints;
+        use crate::unicode_reader::CodePoints;
 
         match self.stream_inst.0.borrow_mut().1 {
             StreamInstance::InputFile(_, ref mut file) => {
@@ -670,6 +779,34 @@ impl Stream {
             }
         }
     }
+
+    #[inline]
+    pub(crate)
+    fn pause_stream(&mut self, buf: Vec<io::Result<char>>) -> io::Result<()> {
+        match self.stream_inst.0.borrow_mut().1 {
+            StreamInstance::PausedPrologStream(ref mut inner_buf, _) => {
+                inner_buf.extend(parser_top_to_bytes(buf)?.into_iter());
+                return Ok(());
+            }
+            _ => {
+            }
+        }
+
+        if !buf.is_empty() {
+            let stream_inst = mem::replace(
+                &mut self.stream_inst.0.borrow_mut().1,
+                StreamInstance::Null,
+            );
+
+            self.stream_inst.0.borrow_mut().1 =
+                StreamInstance::PausedPrologStream(
+                    parser_top_to_bytes(buf)?,
+                    Box::new(stream_inst),
+                );
+        }
+
+        Ok(())
+    }
 }
 
 impl MachineState {
@@ -866,7 +1003,7 @@ impl MachineState {
         stub_name: &'static str,
         stub_arity: usize,
     ) -> Result<PrologStream, MachineStub> {
-        match parsing_stream(stream.clone()) {
+        match parsing_stream(stream) {
             Ok(parsing_stream) => {
                 Ok(parsing_stream)
             }
@@ -1028,35 +1165,11 @@ impl MachineState {
 }
 
 impl Read for Stream {
+    #[inline]
     fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
-        match self.stream_inst.0.borrow_mut().1 {
-            StreamInstance::InputFile(_, ref mut file) => {
-                file.read(buf)
-            }
-            StreamInstance::TcpStream(_, ref mut tcp_stream) => {
-                tcp_stream.read(buf)
-            }
-            StreamInstance::ReadlineStream(ref mut rl_stream) => {
-                rl_stream.read(buf)
-            }
-            StreamInstance::DynReadSource(ref mut src) => {
-                src.read(buf)
-            }
-            StreamInstance::Bytes(ref mut cursor) => {
-                cursor.read(buf)
-            }
-/*
-            StreamInstance::Stdin => {
-                stdin().read(buf)
-            }
-*/
-            StreamInstance::OutputFile(..) | StreamInstance::Stdout | StreamInstance::Null => {
-                Err(std::io::Error::new(
-                    ErrorKind::PermissionDenied,
-                    StreamError::ReadFromOutputStream,
-                ))
-            }
-        }
+        let bytes_read = self.stream_inst.0.borrow_mut().1.read(buf)?;
+        self.unpause_stream();
+        Ok(bytes_read)
     }
 }
 
@@ -1069,14 +1182,20 @@ impl Write for Stream {
             StreamInstance::TcpStream(_, ref mut tcp_stream) => {
                 tcp_stream.write(buf)
             }
+            StreamInstance::TlsStream(_, ref mut tls_stream) => {
+                tls_stream.write(buf)
+            }
             StreamInstance::Bytes(ref mut cursor) => {
                 cursor.write(buf)
             }
             StreamInstance::Stdout => {
                 stdout().write(buf)
             }
-            StreamInstance::DynReadSource(_) | StreamInstance::ReadlineStream(_) |
-            StreamInstance::InputFile(..) | StreamInstance::Null => {
+            StreamInstance::PausedPrologStream(..) |
+            StreamInstance::StaticStr(_) |
+            StreamInstance::ReadlineStream(_) |
+            StreamInstance::InputFile(..) |
+            StreamInstance::Null => {
                 Err(std::io::Error::new(
                     ErrorKind::PermissionDenied,
                     StreamError::WriteToInputStream,
@@ -1093,14 +1212,20 @@ impl Write for Stream {
             StreamInstance::TcpStream(_, ref mut tcp_stream) => {
                 tcp_stream.flush()
             }
+            StreamInstance::TlsStream(_, ref mut tls_stream) => {
+                tls_stream.flush()
+            }
             StreamInstance::Bytes(ref mut cursor) => {
                 cursor.flush()
             }
             StreamInstance::Stdout => {
                 stdout().flush()
             }
-            StreamInstance::DynReadSource(_) | StreamInstance::ReadlineStream(_) |
-            StreamInstance::InputFile(..) | StreamInstance::Null => {
+            StreamInstance::PausedPrologStream(..) |
+            StreamInstance::StaticStr(_) |
+            StreamInstance::ReadlineStream(_) |
+            StreamInstance::InputFile(..) |
+            StreamInstance::Null => {
                 Err(std::io::Error::new(
                     ErrorKind::PermissionDenied,
                     StreamError::FlushToInputStream,

src/machine/term_expansion.rs

@@ -1,10 +1,10 @@
-use prolog_parser::ast::*;
-use prolog_parser::parser::*;
+use crate::prolog_parser::ast::*;
+use crate::prolog_parser::parser::*;
 
-use crate::prolog::machine::machine_indices::HeapCellValue;
-use crate::prolog::machine::*;
-use crate::prolog::rug::ops::Pow;
-use crate::prolog::rug::Integer;
+use crate::machine::machine_indices::HeapCellValue;
+use crate::machine::*;
+use crate::rug::ops::Pow;
+use crate::rug::Integer;
 
 use std::cell::Cell;
 use std::collections::VecDeque;
@@ -165,7 +165,7 @@ impl<'a> TermStream<'a> {
 
     #[inline]
     pub fn eof(&mut self) -> Result<bool, ParserError> {
-	self.parser.devour_whitespace()?; // eliminate dangling comments before checking for EOF.
+	    self.parser.devour_whitespace()?; // eliminate dangling comments before checking for EOF.
         Ok(self.stack.is_empty() && self.parser.eof()?)
     }
 

src/machine/toplevel.rs

@@ -1,14 +1,14 @@
-use prolog_parser::ast::*;
-use prolog_parser::tabled_rc::*;
+use crate::prolog_parser::ast::*;
+use crate::prolog_parser::tabled_rc::*;
 
-use crate::prolog::forms::*;
-use crate::prolog::iterators::*;
-use crate::prolog::machine::machine_errors::*;
-use crate::prolog::machine::machine_indices::*;
-use crate::prolog::machine::term_expansion::*;
-use crate::prolog::machine::*;
+use crate::forms::*;
+use crate::iterators::*;
+use crate::machine::machine_errors::*;
+use crate::machine::machine_indices::*;
+use crate::machine::term_expansion::*;
+use crate::machine::*;
 
-use indexmap::{IndexMap, IndexSet};
+use crate::indexmap::{IndexMap, IndexSet};
 
 use std::borrow::BorrowMut;
 use std::cell::Cell;
@@ -340,16 +340,37 @@ fn setup_module_decl(
     }
 }
 
-fn setup_use_module_decl(mut terms: Vec<Box<Term>>) -> Result<ModuleSource, ParserError> {
+fn read_library_path(
+    term: Term,
+    atom_tbl: TabledData<Atom>,
+) -> Option<ClauseName> {
+    match term {
+        Term::Constant(_, Constant::Atom(atom, _)) => {
+            Some(atom.defrock_brackets())
+        }
+        _ => {
+            let mut atoms = vec![];
+
+            for term in unfold_by_str(term, "/") {
+                match term {
+                    Term::Constant(_, Constant::Atom(atom, _)) => {
+                        atoms.push(atom.as_str().to_owned());
+                    }
+                    _ => return None,
+                }
+            }
+
+            Some(clause_name!(atoms.join("/"), atom_tbl))
+        }
+    }
+}
+
+fn setup_use_module_decl(mut terms: Vec<Box<Term>>, atom_tbl: TabledData<Atom>) -> Result<ModuleSource, ParserError> {
     match *terms.pop().unwrap() {
         Term::Clause(_, ref name, ref mut terms, None)
             if name.as_str() == "library" && terms.len() == 1 =>
         {
-            terms
-                .pop()
-                .unwrap()
-                .to_constant()
-                .and_then(|c| c.to_atom())
+            read_library_path(*terms.pop().unwrap(), atom_tbl)
                 .map(|c| ModuleSource::Library(c))
                 .ok_or(ParserError::InvalidUseModuleDecl)
         }
@@ -396,11 +417,7 @@ fn setup_qualified_import(
         Term::Clause(_, ref name, ref mut terms, None)
             if name.as_str() == "library" && terms.len() == 1 =>
         {
-            terms
-                .pop()
-                .unwrap()
-                .to_constant()
-                .and_then(|c| c.to_atom())
+            read_library_path(*terms.pop().unwrap(), atom_tbl.clone())
                 .map(|c| ModuleSource::Library(c))
                 .ok_or(ParserError::InvalidUseModuleDecl)
         }
@@ -685,7 +702,7 @@ fn setup_declaration<'a, 'b, 'c>(
                     }
                 }
 		        ("use_module", 1) => {
-		            Ok(Declaration::UseModule(setup_use_module_decl(terms)?))
+		            Ok(Declaration::UseModule(setup_use_module_decl(terms, indices.atom_tbl())?))
                 }
 		        ("use_module", 2) => {
 		            let (name, exports) = setup_qualified_import(terms, indices.atom_tbl())?;

src/macros.rs

@@ -121,6 +121,9 @@ macro_rules! functor_term {
     (atom($e:expr), $arity:expr, $aux_lens:expr, $addendum: ident) => (
         HeapCellValue::Atom(clause_name!($e), None)
     );
+    (value($e:expr), $arity:expr, $aux_lens:expr, $addendum: ident) => (
+        $e
+    );
     (string($h:expr, $e:expr), $arity:expr, $aux_lens:expr, $addendum: ident) => ({
         let len: usize = $aux_lens.iter().sum();
         let h = len + $arity + 1 + $addendum.h() + $h;

src/main.rs

@@ -1,3 +1,6 @@
+extern crate blake2;
+extern crate chrono;
+extern crate cpu_time;
 extern crate crossterm;
 extern crate divrem;
 #[macro_use]
@@ -8,19 +11,45 @@ extern crate indexmap;
 #[macro_use]
 extern crate lazy_static;
 extern crate libc;
+extern crate native_tls;
 extern crate nix;
+extern crate openssl;
+extern crate ordered_float;
 #[macro_use]
 extern crate prolog_parser;
 #[macro_use]
 extern crate ref_thread_local;
+extern crate ring;
+extern crate ripemd160;
+extern crate rug;
+extern crate rustyline;
+extern crate sha3;
+extern crate unicode_reader;
 
-use nix::sys::signal;
+use crate::nix::sys::signal;
 
-mod prolog;
+#[macro_use]
+mod macros;
+mod allocator;
+mod arithmetic;
+mod codegen;
+mod clause_types;
+mod debray_allocator;
+mod fixtures;
+mod forms;
+mod heap_iter;
+mod heap_print;
+mod indexing;
+mod instructions;
+mod iterators;
+mod machine;
+mod read;
+mod targets;
+mod write;
 
-use crate::prolog::machine::*;
-use crate::prolog::machine::streams::*;
-use crate::prolog::read::*;
+use machine::*;
+use machine::streams::*;
+use read::*;
 
 use std::sync::atomic::Ordering;
 

src/mod.rs

@@ -5,7 +5,6 @@ extern crate prolog_parser;
 extern crate rug;
 #[cfg(feature = "num-rug-adapter")]
 extern crate num_rug_adapter as rug;
-extern crate rustyline;
 
 #[macro_use]
 mod macros;

src/prolog/examples/utf8.pl

@@ -1,15 +0,0 @@
-:- 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].
-
-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).

src/prolog/lib/pio.pl

@@ -1,24 +0,0 @@
-:- module(pio, [phrase_from_file/2,
-                phrase_from_file/3]).
-
-:- use_module(library(dcgs)).
-:- use_module(library(error)).
-:- 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
-        ),
-        '$file_to_chars'(File, Chars, Type),
-        phrase(NT, Chars)
-    ).