All Manuals > KnowledgeWorks and Prolog User Guide > 7 Reference Guide

NextPrevUpTopContentsIndex

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 (Unix version) - 26 Feb 2015

NextPrevUpTopContentsIndex