eyeprolog

ISO/IEC 13211-1 implementation-defined and implementation-specific profile

This is the clause-by-clause ISO 5.4 decision index for EyeProlog. The normative baseline used for this table is ISO/IEC 13211-1:1995 together with Technical Corrigenda 1:2007, 2:2012, and 3:2017. The current WG17/STC pages at complang.tuwien.ac.at are useful review input, but draft proposals are not silently treated as normative changes to that licensed baseline.

The Art of EyeProlog remains the single implementation reference. This file is an audit index: it identifies each explicitly implementation-defined decision in Part 1, states the EyeProlog choice, and points to the implementation boundary that realizes it. Repeated references to the same decision are folded into one row. Requirements that the standard calls implementation dependent are listed separately because ISO 5.4 does not require their documentation in the same way.

Status values are:

Explicit implementation-defined decisions

Clause Decision completed by ISO 5.4 documentation EyeProlog choice Status / implementation evidence
5.5.11 Reserved atoms and the effect of instantiating a variable to one EyeProlog reserves no Prolog atom under 5.5.11. Atoms with implementation-looking names remain ordinary terms unless a particular predicate interprets them. defined — term representation and built-ins in src/term.js, src/iso.js.
6.5 Processor character set (PCS) EyeProlog’s PCS is the Unicode scalar repertoire U+0000..U+10FFFF excluding surrogates. This implementation-defined processor choice is shared by normal and --iso-strict modes; strict conformance does not narrow it. defined — src/iso-character.js, parser/character-I/O validation, and strict-core/WG17 coverage.
6.5 Classification of additional/extended PCS characters Printable ASCII uses the lexical classes specified by Part 1. C0 controls and DEL are extended layout characters. Non-ASCII Unicode letters extend alphanumeric name syntax; Unicode white-space is layout; remaining non-ASCII symbols/punctuation are extended graphic characters. defined — src/parser.js, src/syntax-scan.js, src/iso-character.js.
6.6 Collating-sequence integers Each PCS character’s collating-sequence integer is its Unicode scalar value. Atom/functor comparison is lexicographic by those scalar integers, satisfying the required monotonic ASCII capital-letter, small-letter, and contiguous decimal-digit constraints while remaining well-defined for supplementary characters. defined — src/iso-character.js, src/term.js (compareTerms), src/iso.js character-code predicates.
6.6 Collating values of control escapes and extended characters Control escapes, octal/hexadecimal escapes, character-code constants, and extended Unicode characters all use the denoted Unicode scalar value as collating integer. defined — src/iso-character.js, parser escape handling, char_code/2, atom_codes/2, and WG17 escape cases.
7.1.2.2 Mapping between a character code and bytes Text file streams decode and encode UTF-8. Binary streams expose bytes 0..255 directly. defined — src/io.js.
7.1.4.1 Set C of characters represented by one-char atoms In both profiles C is the Unicode scalar repertoire U+0000..U+10FFFF excluding surrogates. defined — src/iso-character.js, src/iso.js character-code validation.
7.4.2.4 Whether op/3 directives affect other Prolog texts or execution An op/3 directive changes parsing of subsequent text loaded into the same Program; the resulting operator table is also used by execution-time term I/O. Separately created Program objects are independent. defined — src/parser.js, src/program.js, src/iso.js.
7.4.2.5 Whether directive-created Convc affects other text/execution Yes. A char_conversion/2 directive updates preparation-time conversion for later unquoted source characters and the recorded mapping initializes execution-time term input. Quoted characters are not converted; char_conversion=off disables following preparation-time conversion. defined — src/parser.js, src/program.js, src/solver.js; strict-core regression coverage.
7.4.2.6 Order of initialization/1 goals Initialization goals run once per prepared Program, in source/inclusion order, before requested goals; each must obtain a first solution. Reusing the same prepared program in another solver does not execute its initialization goals again. defined — Program.initializations, preparation state, Solver.runInitializations().
7.4.2.7 Ground term designating a Prolog text for include/1 A source designation is an atom interpreted as a file path; relative paths resolve from the including file’s directory (or the current working directory for unanchored input). defined — src/program.js (readIncludedSource).
7.4.2.8 Ground term designating a Prolog text for ensure_loaded/1 Same atom/file-path designation as include/1. defined — src/program.js.
7.4.2.8 Position at which an ensured text is included The first ensure_loaded/1 expands the text in place at the directive; later requests for the same resolved path are ignored. defined — src/program.js (ensured set and in-place builder loading).
7.4.2.9 Whether set_prolog_flag/2 directives affect other texts/execution Parser-relevant double_quotes changes following source text in the same parse; recorded flag directives initialize the solver used for execution. Separately created programs/solvers are independent. defined — src/parser.js, src/program.js, src/solver.js.
7.5.1 Means by which the processor is asked to prepare Prolog text Text is prepared through the CLI/REPL, the JavaScript Program.parse/run API, source files/URLs, and include/1/ensure_loaded/1. defined — Chapter 40 and src/cli.js, src/index.js, src/program.js.
7.5.1 Effects of directive-driven reordering, addition, or removal of clauses during preparation Includes are expanded in place; declarations annotate the affected procedure; clauses otherwise retain source order. No directive silently reorders ordinary clauses. defined — streaming builder in src/program.js.
7.7.1 External form of a negative answer The interactive top level prints false.. Non-interactive run()/CLI corpus execution emits no answer line for a failed goal. defined — Chapter 40, src/repl.js, src/execute.js.
7.7.1 External form of a positive answer The REPL prints true. for a solution without visible bindings or Name = Term bindings; the file/API runner emits each resolved ground goal as a Prolog term followed by .. defined — Chapter 40, src/repl.js, src/execute.js.
7.7.3 Method by which a user delivers a goal REPL queries, CLI --goal, %% goal: host comments, and the JavaScript goal option are supported host interfaces. defined — Chapter 40.
7.10.1 Additional source/sink possibilities Node runtimes support local files plus the predefined standard streams; embedding supplies user_input text and a user_output callback. URL loading is a source-loading facility, not an ISO stream opened by open/4. defined — src/io.js, src/cli.js, src/index.js.
7.10.1 Ground term designating a source/sink to open/4 An atom is interpreted as a local file-system path. defined — src/iso.js, src/io.js.
7.10.2.6 Record-based/non-record-based text stream support EyeProlog exposes non-record-based text streams. defined — src/io.js.
7.10.2.6 Alteration of spaces at line ends None. EyeProlog preserves text-stream characters; it does not trim or pad line endings. defined — src/io.js.
7.10.2.6 Whether the last line is followed by newline / close adds one Closing a text output stream writes exactly the accumulated content and does not synthesize a final newline. defined — StreamManager.close().
7.10.2.6 Effect of outputting control characters The Unicode character is appended unchanged to a text stream (subject to the host sink’s ordinary string handling). defined — StreamManager.writeUnit().
7.10.2.7 Number of zero bytes that may be appended on binary re-input Zero. Binary file output is written and read byte-for-byte. defined — src/io.js.
7.10.2.8 Whether a source/sink can be arbitrarily repositioned File streams are repositionable only when opened with reposition(true); standard streams are not repositionable. defined — src/io.js, set_stream_position/2 in src/iso.js.
7.10.2.9 Terms denoting end/past-end stream positions when repositionable Stream positions are non-negative integer offsets; position(N) is also accepted by set_stream_position/2. End/past-end state is separately exposed by end_of_stream/1. defined — streamProperties() and setStreamPositionBuiltin() in src/iso.js.
7.10.2.11 Default eof_action Newly opened file streams default to error. The predefined standard streams use reset. defined — src/io.js.
7.10.2.13 eof_action(Action) property when the stream uses its default action Reports the same selected action: error for ordinary opened files and reset for the predefined standard streams. defined — streamProperties() in src/iso.js, defaults in src/io.js.
7.10.2.11 Whether reposition(false) streams may nevertheless be repositioned No. set_stream_position/2 raises a permission error unless the stream was created with reposition(true). defined — src/iso.js.
7.11.1.1 Default bounded flag false: EyeProlog’s Prolog integer model uses arbitrary-precision BigInt, subject to host resources. The standard values remain true and false; because this flag is fixed, selecting either value through set_prolog_flag/2 reaches the standard non-changeable-flag rule rather than narrowing the value domain to the current choice. defined — defaultPrologFlags() in src/solver.js; strict flag tests.
7.11.1.2 Default max_integer when bounded=true Not applicable because EyeProlog selects bounded=false; consequently current_prolog_flag(max_integer, _) fails. not applicable — src/solver.js, current_prolog_flag/2; strict-core regression coverage.
7.11.1.3 Default min_integer when bounded=true Not applicable because EyeProlog selects bounded=false; consequently current_prolog_flag(min_integer, _) fails. not applicable — src/solver.js, current_prolog_flag/2; strict-core regression coverage.
7.11.1.4 Default integer_rounding_function flag toward_zero; // uses truncation toward zero. The standard flag values are down and toward_zero, but the selected flag is non-changeable; an attempt to select the other valid value is therefore a permission error. div is provided separately with downward/floor division semantics. defined — src/solver.js, src/iso-arithmetic.js; strict flag tests.
9.1.3.1 Integer division rounding function rndI Truncation toward zero, matching the integer_rounding_function=toward_zero flag. defined — BigInt division for // in src/iso-arithmetic.js.
7.11.2.1 Whether preparation-time Convc affects execution-time Convc Yes: mappings created while Prolog text is prepared are retained and initialize the solver’s execution-time conversion map. defined — src/parser.js, src/program.js, src/solver.js.
7.11.2.2 Effect when debug=on The flag is accepted and stored; it does not change goal semantics or enable a debugger. defined — src/solver.js; no semantic branch depends on debug.
7.11.2.3 Default max_arity unbounded: EyeProlog imposes no fixed semantic ceiling on compound-term arity. Practical host allocation exhaustion is a resource condition. This flag is distinct from any potential implementation-specific procedure-arity limit; EyeProlog currently declares no separate finite procedure limit. defined — src/iso-limits.js, src/solver.js, src/parser.js, src/iso.js; strict regression coverage.
7.11.2.5 Default double_quotes chars. defined — src/solver.js, parser flag state.
7.12.1 Second argument of error/2 The default context term is the atom eyeprolog. A few implementation-specific diagnostics may deliberately supply a more specific context term. defined — formalErrorTerm() in src/iso.js.
7.12.2(f) Implementation-defined representation limits Character and character-code operations are limited to Unicode scalar values; surrogates and values above U+10FFFF are representation errors. Arity/integer values are modeled as unbounded but may hit host/resource limits. Float input overflow uses the implementation-specific max_float/min_float representation names documented by the STC-oriented tests. defined — parser/ISO numeric and character guards.
8.17.1 Implementation-defined flag value ranges Strict mode exposes only Part 1 core flags and their standard value sets. Normal mode additionally exposes EyeProlog’s occurs_check flag. With bounded=false, max_integer and min_integer have no current or selectable value and their current_prolog_flag/2 queries fail. Valid alternative values of fixed standard flags are distinguished from invalid values so set_prolog_flag/2 reports permission versus domain errors as prescribed. defined — strict registry/flag filtering in src/solver.js; strict flag tests.
8.17.3 Other effects of halt/0 Terminates EyeProlog execution and returns host/process status 0; it produces no Prolog solution. defined — HaltSignal, haltBuiltin(), CLI/runner handling.
8.17.4 Meaning/effects of halt(Status) Integer Status is converted to the host process/runner halt code; it produces no Prolog solution. defined — haltBuiltin(), src/execute.js, src/cli.js.
9.1.4.1 Floating-point rounding function rndF Floating values and operations use ECMAScript Number (IEEE-754 binary64) and the host’s specified binary64 arithmetic/conversions. defined — src/iso-arithmetic.js, src/number-value.js.
9.1.4.2 Floating-point result function for operations whose result is governed only by resultF EyeProlog chooses round(x) rather than the optional exceptional value underflow. ECMAScript binary64 arithmetic therefore preserves a representable subnormal result and rounds a still-smaller generic arithmetic result to 0.0, consistently with float-token, number_chars/2, and number_codes/2 input. The published Part 1 **/2 and Corrigendum 2 ^/2 tables still contain separate unconditional underflow rows, which strict mode retains; post-N289 STC #75 proposes making those two power rows conditional on this resultF choice and is tracked separately as draft work. exp/1 has its own published exceptional condition and is not the subject of STC #75. defined — arithmetic evaluation in src/iso-arithmetic.js and parser/number conversion; strict exceptional-value regressions.
9.1.4.3 Approximate-addition function ECMAScript binary64 addition is used; subtraction is implemented through the corresponding host operation and all finite results remain binary64 values. defined — arithmetic evaluation in src/iso-arithmetic.js.
9.4 Representation of negative integers for bitwise operations BigInt’s unbounded signed binary semantics are used, equivalent to an infinite two’s-complement sign extension for bitwise operations. defined — src/iso-arithmetic.js BigInt bitwise operators and strict Clause 9.4 boundary regressions.
9.4.1 Right shift of negative integers and unusual shift counts >> is arithmetic/sign-propagating. A negative count reverses direction according to JavaScript BigInt shift semantics; there is no finite integer bit-size ceiling in the Prolog model. defined — a >> b in src/iso-arithmetic.js; strict regressions pin negative operands/counts.
9.4.2 Left shift of negative integers and unusual shift counts << uses BigInt signed shift semantics; a negative count reverses direction. Resource exhaustion remains possible for very large results. defined — a << b in src/iso-arithmetic.js; strict regressions pin negative counts and resource exhaustion.
9.4.3 Bitwise AND with negative operands BigInt infinite-two’s-complement semantics. defined — a & b.
9.4.4 Bitwise OR with negative operands BigInt infinite-two’s-complement semantics. defined — a \| b.
9.4.5 Bitwise complement BigInt complement, i.e. ~N = -N-1. defined — ~a.
Cor.2 9.4.6 xor/2 with negative operands BigInt infinite-two’s-complement semantics. defined — a ^ b.

Floating underflow policy

Clause 9.1.4.2 permits the processor to choose round(x) or the exceptional value underflow for a tiny non-zero result when an operation is governed by the generic floating result function. EyeProlog chooses round(x). Because its floating-point profile is ECMAScript IEEE-754 binary64, representable subnormal values remain non-zero and still-smaller generic results round to 0.0. Float-token and number_chars/2 input use the same finite-double rounding policy.

That generic implementation-defined choice is distinct from the currently published evaluable-functor error clauses. In the licensed Part 1 + Corrigenda baseline, exp/1, Part 1 **/2, and Corrigendum 2 ^/2 have explicit underflow conditions, so strict mode raises evaluation_error(underflow) when those published conditions are met. The 2026-08-23 post-N289 draft adds STC #75, proposing that the two power underflow rows apply only when the processor selects underflow in 9.1.4.2. EyeProlog records that proposal but does not silently replace the published strict baseline with it. The regression suite pins both the published power behavior and the generic round-to-zero choice; stc/float_underflow_input covers the separate input-conversion policy.

Implementation-specific features required to be documented by 5.4

Part 1 clause 5.5 permits extensions only as implementation-specific features. Corrigendum 3 additionally makes extra option names explicit implementation- specific features. EyeProlog’s normal profile provides the following extension families; --iso-strict is intended to remove their Part 1 interpretation.

Part 1 extension hook EyeProlog normal-profile feature Strict-core disposition
5.5.1 Syntax Part 2 modules, Part 3 grammar-rule expansion, and embedded quad syntax Module directives are rejected; grammar rules remain ordinary -->/2 terms rather than being expanded; quad syntax is rejected. Unicode PCS membership/classification is implementation defined and therefore shared with normal mode rather than treated as an extension.
5.5.2 Predefined operators Part 3 | and EyeProlog’s labelable infix (?-)/2; CLP(Z) operators when that library is imported Only the Part 1 operator table is predefined; a conforming op/3 may still add permitted operators.
5.5.3 Character-conversion mapping No non-identity initial Convc extension Identity initial mapping.
5.5.4 Types The normal JavaScript API exposes an implementation-specific string term stringTerm(Text). It is disjoint from the five Part 1 term types; normal term order places it after atoms and before compound terms, and normal atomic/1 treats it as atomic. It has no Prolog source token syntax (double-quoted source still follows double_quotes), is non-callable for term-to-clause conversion, is not evaluable as an arithmetic expression, and writes as a double-quoted host string. Strict mode rejects a programmatic string term at program/goal entry with representation_error(term), so the additional type cannot enter the Part 1 execution domain. defined — src/term.js, src/program.js, src/solver.js; strict API-boundary regression.
5.5.5 Directives module/2, use_module/1-2, meta_predicate/1 and normal-profile library behavior Rejected as implementation-specific Part 1 directives.
5.5.6 Side effects Normal mode adds statistics/0-2, cleanup/library state, and optional proof/statistics host instrumentation. The strict registry excludes Prolog-visible statistics/cleanup/library adapters; ordinary Part 1 I/O/database/flag/operator side effects remain. Host proof/statistics collection observes execution through the embedding API rather than adding a strict Prolog goal effect. covered — strict registry/execution regression.
5.5.7 Control constructs tnot/1 and normal-profile execution optimizations tnot/1 is absent; automatic tabling/recursion guards are disabled.
5.5.8 Flags occurs_check Absent in strict mode.
5.5.9 Built-in predicates EyeProlog libraries, CLP(Z), statistics, Part 3 phrase/2-3, and interop autoloaded predicates Strict registry contains only the Part 1 + Corrigenda core registry.
5.5.10 Evaluable functors Normal mode additionally accepts the EyeProlog evaluable atom e; the remaining arithmetic functors accepted by strict mode are the Part 1 + Corrigenda set. Strict mode rejects e/0 as non-evaluable and retains the Corrigendum arithmetic additions. covered — strict extension-boundary regression plus src/iso-arithmetic.js.
5.5.11 Reserved atoms None None.
Cor.3 5.5.12 Options Extra library/host options may exist outside core option lists Normal mode additionally accepts the EyeProlog write_term/2-3 options double_quotes(true|false) and spacing(true|false). spacing(false) emits only lexically required separators; spacing(true) adds conventional layout around operators. Strict core excludes these implementation-specific extensions and accepts only the Part 1 plus Corrigendum 3 write-option surface; unknown extension options raise domain_error(write_option,...).

Normal mode provides documented module and DCG compatibility profiles whose features overlap standardized Part 2 and Part 3 facilities. They are extensions relative to the Part 1 strict-core boundary and are tested separately; this ledger does not assert complete Part 2 or Part 3 conformance.

Important implementation-dependent behavior (not the 5.4 mandatory table)

For portability work, EyeProlog also documents these choices even though the 1995 text labels them implementation dependent, not implementation defined:

These rows are intentionally separate so that the ISO 5.4 checklist does not blur the standard’s distinction between implementation defined (documented), implementation dependent (need not be documented), and implementation specific (an extension that must be documented for a conforming processor).

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