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fail

Backward Chaining Goal
Summary

The standard prolog predicate that always fails.

Signature

fail

Description

This goal always fails. It is sometimes used with cut.

Examples
(defrule nice :backward
  ((nice ?x)
   <--
   (rottweiler ?x)
   (cut)
   (fail))
  ((nice ?x) <--))

implements "everything is nice unless it is a rottweiler".

See also

cut


KnowledgeWorks and Prolog User Guide (Macintosh version) - 24 Mar 2017

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