occurs.pl -- Finding and counting sub-terms

This is a SWI-Prolog implementation of the corresponding Quintus library, based on the generalised arg/3 predicate of SWI-Prolog.

See also

- library(terms) provides similar predicates and is probably more wide-spread than this library.

 contains_term(+Sub, +Term) is semidet

Succeeds if Sub is contained in Term (=, deterministically)

 contains_var(+Sub, +Term) is det

Succeeds if Sub is contained in Term (==, deterministically)

 free_of_term(+Sub, +Term)

Succeeds of Sub does not unify to any subterm of Term

 free_of_var(+Sub, +Term)

Succeeds of Sub is not equal (==) to any subterm of Term

 occurrences_of_term(+SubTerm, +Term, ?Count)

Count the number of SubTerms in Term

 occurrences_of_var(+SubTerm, +Term, ?Count)

Count the number of SubTerms in Term

 sub_term(-Sub, +Term)

Generates (on backtracking) all subterms of Term.

 sub_var(-Sub, +Term)

Generates (on backtracking) all subterms (==) of Term.