(VAR X X1 X2 Y Z )
(RULES 
        primes -> sieve(from(s(s(0))))
        from(X) -> cons(X, n__from(s(X)))
        head(cons(X, Y)) -> X
        tail(cons(X, Y)) -> activate(Y)
        if(true, X, Y) -> activate(X)
        if(false, X, Y) -> activate(Y)
        filter(s(s(X)), cons(Y, Z)) -> if(divides(s(s(X)), Y), n__filter(s(s(X)), activate(Z)), n__cons(Y, n__filter(X, sieve(Y))))
        sieve(cons(X, Y)) -> cons(X, n__filter(X, sieve(activate(Y))))
        from(X) -> n__from(X)
        filter(X1, X2) -> n__filter(X1, X2)
        cons(X1, X2) -> n__cons(X1, X2)
        activate(n__from(X)) -> from(X)
        activate(n__filter(X1, X2)) -> filter(X1, X2)
        activate(n__cons(X1, X2)) -> cons(X1, X2)
        activate(X) -> X
        
)