built-in method
once/1
¶
Description¶
once(Goal)
This predicate behaves as call(Goal)
but it is not re-executable.
This built-in meta-predicate is declared as a private method and thus
cannot be used as a message to an object.
This meta-predicate is opaque to cuts in its argument.
Modes and number of proofs¶
once(+callable) - zero_or_one
Errors¶
Goal
is a variable:instantiation_error
Goal
is neither a variable nor a callable term:type_error(callable, Goal)