NO Problem: nats() -> adx(zeros()) zeros() -> cons(0(),zeros()) incr(cons(X,Y)) -> cons(s(X),incr(Y)) adx(cons(X,Y)) -> incr(cons(X,adx(Y))) hd(cons(X,Y)) -> X tl(cons(X,Y)) -> Y Proof: Containment Processor: loop length: 1 terms: zeros() context: cons(0(),[]) substitution: Qed