(VAR X Y X1 X2) (RULES from(X) -> cons(X,n__from(n__s(X))) length(n__nil) -> 0 length(n__cons(X,Y)) -> s(length1(activate(Y))) length1(X) -> length(activate(X)) from(X) -> n__from(X) s(X) -> n__s(X) nil -> n__nil cons(X1,X2) -> n__cons(X1,X2) activate(n__from(X)) -> from(activate(X)) activate(n__s(X)) -> s(activate(X)) activate(n__nil) -> nil activate(n__cons(X1,X2)) -> cons(activate(X1),X2) activate(X) -> X )