cons :: c → d → d
f :: a → a
false :: b
filter :: (c → b) → d → d
filter2 :: b → (c → b) → c → d → d
g :: a → a
map :: (c → c) → d → d
nil :: d
true :: b
f(g(X)) → g(g(f(X)))
f(g(Y)) → g(g(g(Y)))
map(G, nil) → nil
map(H, cons(W, P)) → cons(H(W), map(H, P))
filter(F1, nil) → nil
filter(Z1, cons(U1, V1)) → filter2(Z1(U1), Z1, U1, V1)
filter2(true, I1, P1, X2) → cons(P1, filter(I1, X2))
filter2(false, Z2, U2, V2) → filter(Z2, V2)