ref: 6dd50f970be88637fd2799ae8e2868c01002898e
dir: /stdlib.pl/
:- module(system, []). % Logic and control predicates \+ Goal :- call(Goal), !, fail. \+ Goal. once(Goal) :- call(Goal), !. repeat :- true ; repeat. % Control structures. true. If -> Then :- If, !, Then. If -> Then ; _ :- If, !, Then. _ -> _ ; Else :- !, Else. If ; _ :- If. _ ; Else :- Else. A , B :- A , B. % Term unification A = A. A \= B :- \+ A = B. % Comparison of terms using the standard order A == B :- compare(=, A, B). A \== B :- \+ A == B. A @< B :- compare(<, A, B). A @=< B :- A == B. A @=< B :- A @< B. A @> B :- compare(>, A, B). A @>= B :- A == B. A @>= B :- A @> B. % Input output open(SourceSink, Mode, Stream) :- open(SourceSink, Mode, Stream, []). close(StreamOrAlias) :- close(StreamOrAlias, []). % Standard exceptions instantiation_error :- throw(error(instantiation_error, _)). type_error(ValidType, Culprit) :- throw(error(type_error(ValidType, Culprit), _)). domain_error(ValidDomain, Culprit) :- throw(error(domain_error(ValidDomain, Culprit), _)). existence_error(ObjectType, Culprit) :- throw(error(existence_error(ObjectType, Culprit), _)). permission_error(Operation, PermissionType, Culprit) :- throw(error(permission_error(Operation, PermissionType, Culprit), _)). representation_error(Flag) :- throw(error(representation_error(Flag), _)). evaluation_error(Error) :- throw(error(evaluation_error(Error), _)). resource_error(Resource) :- throw(error(resource_error(Resource), _)). syntax_error(Error) :- throw(error(syntax_error(Error), _)). % Input and output read_term(Term, Options) :- current_input(S), read_term(S, Term, Options). read(Term) :- current_input(S), read_term(S, Term, []). write_term(Term, Options) :- current_output(S), write_term(S, Term, Options). write(Term) :- current_output(S), write_term(S, Term, [numbervars(true)]). writeq(Term) :- current_output(S), write_term(S, Term, [quoted(true), numbervars(true)]). writeq(S, Term) :- write_term(S, Term, [quoted(true), numbervars(true)]). write_canonical(Term) :- current_output(S), write_term(S, Term, [quoted(true), ignore_ops(true)]). write_canonical(S, Term) :- write_term(S, Term, [quoted(true), ignore_ops(true)]). % Arithmetic comparisons defined in terms of >=. This is not the most effective way, % but it is fine for now. E1 =:= E2 :- E1 >= E2, E2 >= E1. E1 =\= E2 :- \+ E1 =:= E2. E1 < E2 :- E2 >= E1, E1 =\= E2. E1 =< E2 :- E2 >= E1. E1 > E2 :- E2 < E1. % Clause retrieval and information clause(Head, Body) :- clause(Head, Body, Clauses), member(clause(Head, Body), Clauses). % Basic list predicates member(X, [X|_]). member(X, [_|Tail]) :- member(X, Tail).