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

Built-ins and Evaluable Functors (flowlog.c)

This document lists the built-in predicates and arithmetic evaluable functors implemented by Flowlog (flowlog.c).

Notes:

• “ISO” refers to ISO/IEC 13211-1. Flowlog aims for ISO behavior for the core language and most of these predicates.
• Some entries are Flowlog extensions (especially parallelism and introspection helpers).
• Flowlog is intentionally small: common library predicates (e.g. member/2) are not built in; define them in your program if you need them.
• Flowlog has multiple engines (flowlog_engine=wam, flowlog_engine=wamvm, and flowlog_engine=interp/tree). When the active engine cannot safely execute a query it may fall back; see IMPLEMENTATION.md.

Code references (section markers in flowlog.c):

• Builtin dispatch: SECTION 22 (interp), SECTION 23 (WAM-lite), SECTION 24 (WAMVM)
• Unification and term ops: SECTIONS 12/14/15
• Term ordering: SECTION 16
• Arithmetic evaluation: SUBSECTION 15.2
• Streams and term I/O: SECTION 08 and SUBSECTION 17.5
• Inference limits and exceptions: SECTION 19 (SUBSECTION 19.2)
• Packed strings for char lists: SECTION 11

Built-in predicates (SECTIONS 22/23/24)

Control and meta-call (SECTIONS 22/23/24)

• true/0
• fail/0
• false/0
• !/0
• repeat/0
• call/1..8
• once/1
• (\+)/1
• ','/2
• (';')/2
• (->)/2
• (:)/2
• catch/3
• throw/1
• call_with_inference_limit/3 (Flowlog extension)
• call_with_inference_limit_par/3 (Flowlog extension)

Inference limits (Flowlog extension, SUBSECTION 19.2 and SECTIONS 22/23/24)

Flowlog provides inference limiting as a lightweight way to classify (some) non-terminating computations without hanging the process (used by quad testing) (SUBSECTION 19.2).

• call_with_inference_limit(Goal, Limit, Result) executes Goal with a per-thread inference cap Limit (integer >= 0; 0 means unlimited).
  • For each solution of Goal, it succeeds and unifies Result = true.
  • If the cap is exceeded, it succeeds once with Result = inference_limit_exceeded and commits (no further solutions).
  • It introduces a local cut boundary (like call/1).
• call_with_inference_limit_par(Goal, Limit, Result) is like call_with_inference_limit/3, but keeps internal OR/AND-parallelism enabled.
  • When running inside a parallel query, Limit is shared across worker threads.

Unification, term identity, and ordering (SECTIONS 12/14/15/16)

• (=)/2
• (\\=)/2
• (==)/2
• (\\==)/2
• (=@=)/2
• (\\=@=)/2
• compare/3
• (@<)/2, (@=<)/2, (@>)/2, (@>=)/2

Term inspection and construction (SECTIONS 12/14/15)

• (=..)/2
• functor/3
• arg/3
• copy_term/2
• term_variables/2
• unify_with_occurs_check/2
• subsumes_term/2
• acyclic_term/1
• ground/1

Type tests (SECTIONS 12/14/15)

• var/1
• nonvar/1
• atom/1
• integer/1
• float/1
• number/1
• atomic/1
• compound/1
• callable/1

Arithmetic (SUBSECTION 15.2)

• is/2
• (<)/2, (=<)/2, (>)/2, (>=)/2
• (=:=)/2, (=\\=)/2
• evaluable_property/2

Atoms, characters, and conversion (SECTION 11 and SECTIONS 22/23/24)

• atom_chars/2
• atom_codes/2
• atom_concat/3
• atom_length/2
• number_chars/2
• number_codes/2
• char_code/2
• sub_atom/5
• sub_string/5
• char_conversion/2
• current_char_conversion/2

Lists and sorting (SECTIONS 11/12/14/15)

• length/2
• sort/2
• msort/2
• keysort/2
• findall/3
• bagof/3
• setof/3

Dynamic database (SECTION 13)

• dynamic/1 (as a predicate and as a load-time directive)
• current_predicate/1
• predicate_property/2
• asserta/1
• assertz/1
• assert/1
• retract/1
• retractall/1
• abolish/1
• clause/2
• numbervars/3

Operators and flags (SECTION 10 and SECTION 05.4)

• op/3 (as a predicate and as a load-time directive)
• current_op/3
• current_prolog_flag/2
• set_prolog_flag/2 (also supported as a load-time directive for a small whitelist)

Streams and term I/O (SECTION 08 and SUBSECTION 17.5)

• current_input/1, current_output/1, current_error/1
• set_input/1, set_output/1, set_error/1
• open/3, open/4
• close/1, close/2
• stream_property/2
• set_stream/2
• set_stream_position/2
• at_end_of_stream/0, at_end_of_stream/1
• get_code/1, get_code/2
• get_char/1, get_char/2
• get_byte/1, get_byte/2
• peek_code/1, peek_code/2
• peek_char/1, peek_char/2
• peek_byte/1, peek_byte/2
• unget_code/1, unget_code/2
• unget_char/1, unget_char/2
• unget_byte/1, unget_byte/2
• put_code/1, put_code/2
• put_char/1, put_char/2
• put_byte/1, put_byte/2
• tab/1, tab/2
• nl/0, nl/1
• flush_output/0, flush_output/1
• read/1, read/2
• read_term/2, read_term/3
• file_to_chars/2 (NUL bytes are returned as integer 0 list elements)
• file_to_bytes/2, file_to_byte/2 (list of integers 0..255)
• write/1, write/2
• writeq/1, writeq/2
• write_canonical/1, write_canonical/2
• write_term/2, write_term/3

Debugging / inspection helpers (SECTIONS 22/23/24 and SECTION 06)

• listing/0, listing/1
• trace/0, notrace/0
• itrace/0, noitrace/0 (Flowlog extension)
• debug/0, nodebug/0
• current_rule/1
• countall/2

Parallelism helpers (Flowlog extensions, SECTIONS 21/22/23/24)

Parallelism is configured via Prolog flags (see PARALLELISM.md), but Flowlog also exposes introspection helpers:

• flowlog_and_safe/2
• flowlog_and_safe_goal/2

Compatibility / stub predicates (SECTION 06 and SECTIONS 22/23/24)

Flowlog keeps a few predicates for compatibility with other builds. In this build they return fixed values:

• flowlog_cpuproc_id/1
• flowlog_n_cpuproc/1
• flowlog_in_cpuproc/1
• flowlog_taskjob_id/1
• flowlog_n_taskjob/1
• flowlog_last_tc_cp_mask/1
• flowlog_last_tc_cp_count/1
• flowlog_last_tc_worker_count/1
• flowlog_last_tc_start_ok/1
• flowlog_last_tc_start_error_code/1
• flowlog_last_tc_start_error_text/1
• flowlog_db_epochs/2

Internal / reserved predicates (SECTIONS 22/23/24 and SUBSECTION 19.2)

These predicates are not ISO Prolog. They are used internally (tests/benchmarks) and may change:

• $flowlog_sleep_ms/1 (deterministic sleep in milliseconds; integer >= 0)
• $flowlog_inference_limit/1 (set per-thread inference cap; integer >= 0)
• $flowlog_inference_limit_shared/1 (set shared inference cap across OR/AND-par threads; integer >= 0)

Evaluable functors (arithmetic expressions, SUBSECTION 15.2)

These functors are accepted by is/2 and numeric comparisons:

Constants (SUBSECTION 15.2)

• pi/0
• e/0
• epsilon/0

Unary (SUBSECTION 15.2)

• (+)/1
• (-)/1
• abs/1
• sign/1
• floor/1
• ceiling/1
• truncate/1
• round/1
• float_integer_part/1
• float_fractional_part/1
• float/1
• (\\)/1 (bitwise not)
• sin/1, cos/1, tan/1
• asin/1, acos/1, atan/1
• sqrt/1, log/1, exp/1

Binary (SUBSECTION 15.2)

• (+)/2
• (-)/2
• (*)/2
• (/)/2
• (//)/2 (truncating integer division)
• rem/2
• div/2 (floor division)
• mod/2
• min/2, max/2
• (/\\)/2 (bitwise and)
• (\\/)/2 (bitwise or)
• xor/2
• (<<)/2, (>>)/2
• (**)/2
• (^)/2
• atan2/2