KnowledgeWorks and Prolog User Guide > A Common Prolog > A.13 Adding Built-in Predicates

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A.13.1 The defdetpred form

The syntax of this form is

(defdetpred < name > < num args > < body >)

which defines a simple predicate that just runs lisp code and doesn't have to unify any variables. Arguments are referenced with: (special-arg <argnum> ) . The body succeeds by default, but if a failure case arises, use: (detpred-fail <name> <num args> ) .

For example

(defdetpred my-integer 1
  (unless (integerp (special-arg 0))
  (detpred-fail my-integer 1)))
KnowledgeWorks and Prolog User Guide (Macintosh version) - 22 Dec 2009

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