'\+'/1

succeeds if the goal fails and fails if the goal succeeds.

\+(+Goal)
\+ +Goal

'\+'/1 makes negation by failure. That means it succeeds if Goal fails and fails if Goal succeeds.

Arguments 

Goal                   goal

Examples

\+fail. Succeeds.
\+integer(4.76) Succeeds.
\+((X=either;X=or)),X=neither_nor Fails.

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, once/1, repeat/0, throw/1.

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