% Family relationships in Prova
% Demonstrating Prova's logic programming capabilities

parent(tom, bob).
parent(tom, liz).
parent(bob, ann).
parent(bob, pat).
parent(liz, jim).

ancestor(X, Y) :- parent(X, Y).
ancestor(X, Y) :- parent(X, Z), ancestor(Z, Y).

:- ancestor(tom, X), println(X), fail.
:- println(done).