Calling an undefined procedure error

    I'am trying to create a predicate p(X) :- X is 10 doing the following

    EC_ref  X;

    post_goal(term(EC_functor(":-",2), term(EC_functor("p",1),X), term(EC_functor("is",2), X, 10)));

    but when i run the program the error "Calling an undefined procedure error p(X) :- X is 10" in module eclipse occur.

    What's wrong?

    Thanks