| executes a goal only once.
once(?Goal)
once/1 works like call/1, but without backtracing.
Arguments
Goal goal
Examples
| once((member(X,[a,b,c]))). |
Succeeds only once with substitution X <- a. |
Standard
This predicate is part of the ISO-Prolog Standard.
See also
abort/0,
break/0,
call/1,
fcall/1,
catch/3,
','(conjunction)/2,
'!'(cut)/0,
';'(disjunction)/2,
fail/0,
true/0,
halt/0/1,
'->'(if-then)/2,
';'(if-then-else)/2,
'\+'(not provable)/1,
repeat/0,
throw/1.
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