== Signature ==
  0 :: Int
  1 :: Int
(+) :: Int -> Int -> Int
 id :: Int -> Int
abs :: Int -> Int

== Laws ==
  1. id x = x
  2. abs 0 = 0
  3. abs 1 = 1
  4. x + 0 = x
  5. 0 + x = x
  6. abs (abs x) = abs x
  7. x + y = y + x
  8. abs (1 + 1) = 1 + 1
  9. (x + y) + z = x + (y + z)
 10. abs x + abs x = abs (x + x)
 11. abs (x + abs x) = x + abs x
 12. abs (1 + abs x) = 1 + abs x
 13. abs (abs x + abs y) = abs x + abs y
 14. abs x + abs (x + x) = abs (x + (x + x))
 15. abs x + abs (x + 1) = abs (x + (x + 1))