explain.pl -- Describe Prolog Terms

The library(explain) describes prolog-terms. The most useful functionality is its cross-referencing function.

?- explain(subset(_,_)).
"subset(_, _)" is a compound term
        Referenced from 2-th clause of lists:subset/2
        Referenced from 46-th clause of prolog_xref:imported/3
        Referenced from 68-th clause of prolog_xref:imported/3
lists:subset/2 is a predicate defined in
        /staff/jan/lib/pl-5.6.17/library/lists.pl:307
        Referenced from 2-th clause of lists:subset/2
        Possibly referenced from 2-th clause of lists:subset/2

Note that the help-tool for XPCE provides a nice graphical cross-referencer.

 explain(@Term) is det

Give an explanation on Term. The argument may be any Prolog data object. If the argument is an atom, a term of the form Name/Arity or a term of the form Module:Name/Arity, explain/1 describes the predicate as well as possible references to it. See also gxref/0.

 explain(@Term, -Explanation) is nondet

True when Explanation is an explanation of Term.

 known_predicate(:Head)[private]

Succeeds if we know anything about this predicate. Undefined predicates are considered `known' for this purpose, so we can provide referenced messages on them.

 explain_predicate(:Head, -Explanation) is det[private]