(STRATEGY
    INNERMOST)

(VAR
    M N X Y)
(DATATYPES
    A = µX.< cons(X, X), 0, s(X) >)
(SIGNATURES
    filter :: [A x A x A] -> A
    sieve :: [A] -> A
    nats :: [A] -> A
    zprimes :: [] -> A)
(RULES
    filter(cons(X,Y),0(),M) ->
      cons(0(),filter(Y,M,M))
    filter(cons(X,Y),s(N),M) ->
      cons(X,filter(Y,N,M))
    sieve(cons(0(),Y)) -> cons(0()
                              ,sieve(Y))
    sieve(cons(s(N),Y)) -> cons(s(N)
                               ,sieve(filter(Y,N,N)))
    nats(N) -> cons(N,nats(s(N)))
    zprimes() ->
      sieve(nats(s(s(0())))))