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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.
| document: http://www.ifcomputer.co.jp/MINERVA/Manual/Reference/Predicates/logic_and_control/once/print_en.html published 2008/12/1 update 2001/2/7 (c) 1996-2006 IF Computer Japan | ||||||||
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