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