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\+ +Goal
Succeeds if Goal cannot be satisfied. Uses negation as failure (synonym of
not/1 and fail_if/1).
- +Goal
- Goal.
Description
Used to fail if the goal Goal can be satisfied. Uses the standard
Prolog form of negation as failure.
May be used to check whether a call Goal succeeds without binding
variables, the call \+ \+ Goal can be used.
Note that:
!/0 does not cut through \+/1.
Fail Conditions
Fails if Goal succeeds.
Resatisfiable
No.
Exceptions
Examples
Success:
\+ fail.
\+ 1 == 2.
\+ X == 1.
\+ \+ X = 1.
% does not bind X
Fail:
\+ X = 1.
\+ true.
\+ 3 == 3.
See Also
fail_if / 1, not / 1, ~ / 1