0 :: a
ack :: a → a → a
cons :: c → d → d
false :: b
filter :: (c → b) → d → d
filter2 :: b → (c → b) → c → d → d
map :: (c → c) → d → d
nil :: d
succ :: a → a
true :: b
ack(0, X) → succ(X)
ack(succ(Y), U) → ack(Y, succ(0))
ack(succ(V), succ(W)) → ack(V, ack(succ(V), W))
map(J, nil) → nil
map(F1, cons(Y1, U1)) → cons(F1(Y1), map(F1, U1))
filter(H1, nil) → nil
filter(I1, cons(P1, X2)) → filter2(I1(P1), I1, P1, X2)
filter2(true, Z2, U2, V2) → cons(U2, filter(Z2, V2))
filter2(false, I2, P2, X3) → filter(I2, X3)