built-in method
(\+)/1
Description
\+ Goal
Not-provable meta-predicate. True iff call(Goal) is false. This
built-in meta-predicate is declared as a private method and thus cannot
be used as a message to an object.
Warning
The argument is always compiled. As a consequence, when the argument
is a control construct (e.g. a conjunction), any meta-variables will
be wrapped with the equivalent to the call/1 control construct.
Note that these semantics differ from the ISO Prolog Core standard
specification for the (\+)/1 built-in predicate.
Modes and number of proofs
\+ +callable - zero_or_one
Errors
Goal is a variable:instantiation_errorGoal is neither a variable nor a callable term:type_error(callable, Goal)Examples
Not-provable goal in the context of the object or category containing the call:
\+ GoalNot-provable goal sent as a message to self:
\+ ::GoalNot-provable goal sent as a message to an explicit object:
\+ Object::Goal