(VAR X Y Z X1 X2)
(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
)