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:- 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)]).
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