  ^ ^                 ^ ^
=(o.o)=  ~byakuren  =(o.o)=
  m m                 m m

ISO Conformance (`flowlog.c`)

Flowlog targets ISO/IEC 13211-1 behavior: if you write portable ISO Prolog, it should run the same here as in other ISO-focused systems.

This document describes the conformance strategy for Flowlog built from flowlog.c.

What “ISO compliant” means here

ISO/IEC 13211-1 defines the language and its built-in predicates. It does not define what an interactive REPL must look like.

Flowlog aims to match ISO semantics for:

Terms, unification, and control constructs
Arithmetic evaluation and ISO error conditions
Dynamic database predicates (asserta/1, assertz/1, retract/1, abolish/1, clause/2, current_predicate/1, …)
Streams and term I/O (open/3, close/1, read_term/3, write_term/3, set_input/1, set_output/1, …)
Prolog flags (current_prolog_flag/2, set_prolog_flag/2) and per-call I/O options

The predicate/flag checklist is tracked in:

ISO_CHECKLIST.md

Non-ISO behavior (top-level UI)

These are deliberate UX choices for the binary and are not part of the ISO language definition:

The REPL prints all solutions (there is no interactive ; prompt).
The REPL supports the common top-level consult shorthand ([file].) as a convenience for loading source files.
Parallelism flags are Flowlog extensions; they can change ordering when enabled (see PARALLELISM.md).

Suites

This directory includes:

A regression runner in tests/
An INRIA ISO suite runner in tests/

Notes:

The suite is downloaded into build/inria_suite/.
tests/setup_inria_suite.sh applies a couple of small, documented normalizations so the suite matches modern ISO-focused systems.
The conformance runner forces classic mode (--engine interp --parallel-profile off) so suite expectations about ordering/side-effects match ISO-focused interpreters.
You can also run the suite under --engine wam (or --engine wamvm) by setting FLOWLOG_ENGINE=wam (or FLOWLOG_ENGINE=wamvm); this is useful for verifying WAM engine coverage.
To ensure the wamvm engine does not fall back to wam, set FLOWLOG_WAMVM_REQUIRE_VM=1 (VM-only mode). Flowlog also provides make test-inria-wamvm-vmonly to lock this in.

Interpreting warnings

Some suite files temporarily set unknown=warning and intentionally call missing predicates to check the flag’s behavior. Flowlog prints a warning in that case; the suite still passes.

The runner tests/run_inria_suite.sh suppresses per-test stderr by default to keep output clean. To show warnings/errors for every file:

FLOWLOG_INRIA_SHOW_STDERR=1 make test-inria

What conformance does not guarantee

Passing the INRIA suite is a strong signal, but it is not a mathematical proof of full ISO compliance. If you find a behavioral mismatch with another ISO-focused system, please reduce it to a small repro program and add it to tests/.