Predicates of ISO-Prolog

• asserta(+Clause) Asserts Clause as the first clause in its predicate.

• assertz(+Clause) Asserts Clause as the last clause in its predicate.

• assert(+Clause) The same as assertz(Clause)

• retract(?Clause) Removes from the predicate a clause that unifies Clause. Upon backtracking, removes the next unifiable clause.

• abolish(+Functor/+Arity) Completely removes the dynamic predicate identified by Functor/Arity from the program area.

• clause(?Head,?Body) It is true if Head and Body unify with the head and the body of a dynamically asserted (or consulted) clause. The body of a fact is true. Gives multiple solutions upon backtracking.

• current_predicate(?Functor/?Arity) It is true if Functor/Arity identifies a defined predicate, whether static or dynamic, in the program area. Gives multiple solutions upon backtracking.