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not +Goal

Succeeds if Goal cannot be satisfied (uses negation as failure).
Goal
Atom or compound term.

Description

Used to fail if Goal succeeds. Uses the standard Prolog form of negation as failure.

To check whether a call Goal succeeds without binding variables, the call not not Goal can be used. Note that !/0 does not cut through not/1.

Modes and Determinism

Modules

This predicate is sensitive to its module context (tool predicate, see @/2).

Fail Conditions

Fails if Goal succeeds

Examples

Success:
      not fail .
      not 1 == 2 .
      not X==1 .
      not not X = 1.
          % does not bind X
Fail:
      not(X=1).
      not(true).
      not(3 == 3).

See Also

\+ / 1, ~ / 1, -> / 2