== Signature ==
  0 :: Int
 id :: Int -> Int
(+) :: Int -> Int -> Int
  f :: Int -> Int -> Int
  g :: Int -> Int -> Int
  h :: Int -> Int -> Int

== Laws ==
  1. id x = x
  2. x + 0 = x
  3. 0 + x = x
  4. x + y = y + x
  5. f x x = f x y
  6. g x y = g y x
  7. g x x = g x y
  8. h y y = h x y
  9. (x + y) + z = x + (y + z)