The argument has to be a goal. If the goal succeed, return "no". If it failed, return "yes".
Example:
a.
?- a. yes.
?- \+ a. no.
?- \+ \+ a. yes.
nota: Similar to predicate not\1
The argument has to be a goal. If the goal succeed, return "no". If it failed, return "yes".
Example:
a.
?- a. yes.
?- \+ a. no.
?- \+ \+ a. yes.
nota: Similar to predicate not\1