(VAR X X1 X2 Y )
(RULES 
        from(X) -> cons(X, n__from(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)
        nil -> n__nil
        cons(X1, X2) -> n__cons(X1, X2)
        activate(n__from(X)) -> from(X)
        activate(n__nil) -> nil
        activate(n__cons(X1, X2)) -> cons(X1, X2)
        activate(X) -> X
        
)