Builtin predicates - Overview

Arithmetic and string operations

is/2, (=:=)/2, (=!=)/2, (<)/2, (<=)/2, (>)/2, (>=)/2, atom_name/2, fperror/1, isnan/1, isinf/1, randomize/0, randomize/1

Classes and objects

class, new, new_class/4, new_object/3

Clause handling

abolish/1, abolish/2, abolish_database/1, asserta/1, asserta/2, assertz/1, assertz/2, clause/2, clause/3, new_database/1, retract/1, retract/2

Directives

(:-)/1, (?-)/1, consult/1, dynamic/1, import/1, initialization/1, load_library/1

Logic and control

(&&)/2, (||)/2, (=>)/2, (<=>)/2, call/1, call/2, catch/3, (,)/2, (!)/0, commit/0, do, (!)/1, (\+)/1, fail/0, false/0, for, halt/0, halt/1, (->)/2, if, in/2, once/1, repeat/0, switch, throw/1, true/0, try, while

Sorting

keysort/2, keysortd/2, msort/2, msortd/2, rkeysort/2, rkeysortd/2, sort/2, sortd/2

Term comparison

(==)/2, (!==)/2, (@<)/2, (@<=)/2, (@>)/2, (@>=)/2

Term creation and decomposition

(.)/2, (=..)/2, arg/3, copy_term/2, functor/3

Term unification

(=)/2, (!=)/2, unifiable/2, unifiable_one_way/2, unify_one_way/2 unify_with_occurs_check/2

Type testing

atom/1, atomic/1, class/1, class/2, compound/1, database/1, float/1, integer/1, nonvar/1, number/1, object/1, object/2, predicate/1, predicate/2, string/1, var/1

Variable assignment

(:=)/2, (::=)/2, (:==)/2, (::==)/2

Compatibility

Many of the builtin predicates share names and behavior with ISO Standard Prolog predicates. Plang is not a strict subset or superset of Standard Prolog and does not pretend to be. It contains additional term types for member variables, strings, and objects. It also has a completely new clause syntax based on C-style procedural programming languages. However, Plang does try to be compatible with the standard when there is no good reason to diverge. The documentation for the builtin predicates indicate where they attempt compatibility with Standard Prolog.

The following book is an excellent reference work on Standard Prolog, and the inspiration for Plang's documentation style: P. Debransart, A. Ed-Dbali, L. Cervoni, "Prolog: The Standard; Reference Manual", Springer-Verlag, 1996, ISBN 3-540-59304-7.

Where Standard Prolog lacks a particular feature, but SWI-Prolog has that feature, we sometimes attempt compatibility with that version of Prolog instead.