[eclipse 10]: anti_unify(a, b, X). X = _65 yes. [eclipse 11]: anti_unify(a, a, X). X = a yes. [eclipse 9]: anti_unify(foo(a,b,c), foo(b,b,b), X). X = foo(_115, b, _98) yes. [eclipse 8]: anti_unify(foo(a,a,a), foo(b,b,b), X). X = foo(_98, _98, _98) yes.