NO Problem: 2nd(cons(X)) -> head(XS) sel(s(N),cons(X)) -> sel(N,XS) from(X) -> cons(X) head(cons(X)) -> X take(0(),XS) -> nil() take(s(N),cons(X)) -> cons(X) sel(0(),cons(X)) -> X Proof: Fresh Variable Processor: loop length: 1 terms: 2nd(cons(X)) context: head([]) substitution: XS -> 2nd(cons(X)) Qed