Haskell Typeclasses Example

Example.hs

data Coord = Coord Integer Integer

-- instance Eq Coord where
--   (==) (Coord x1 y1) (Coord x2 y2) = x1 == x2 && y1 == y2
instance Show Coord where
  show (Coord x y) = "(" ++ show x ++ "," ++ show y ++ ")"

-- instance Eq Coord where
--   (==) c1 c2 = x1 == x2 && y1 == y2
--     where
--       (Coord x1 y1) = c1
--       (Coord x2 y2) = c2
instance Eq Coord where
  c1 == c2 = x1 == x2 && y1 == y2
    where
      (Coord x1 y1) = c1
      (Coord x2 y2) = c2

addCoord :: Coord -> Coord -> Coord
-- addCoord c1 c2 = Coord (x1 + x2) (y1 + y2)
--   where
--     (Coord x1 y1) = c1
--     (Coord x2 y2) = c2
addCoord (Coord x1 y1) (Coord x2 y2) = Coord (x1 + x2) (y1 + y2)

negateCoord :: Coord -> Coord
negateCoord (Coord x y) = Coord (- x) (- y)

multCoord :: Coord -> Coord -> Coord
multCoord (Coord x1 y1) (Coord x2 y2) = Coord (x1 * x2) (y1 * y2)

absCoord :: Coord -> Coord
absCoord (Coord x y) = Coord (abs x) (abs y)

sigNumCoord :: Coord -> Coord
sigNumCoord (Coord x y) = Coord v v where v = signum x * signum y

instance Num Coord where
  (+) = addCoord
  negate = negateCoord
  (*) = multCoord
  abs = absCoord
  signum = sigNumCoord
  fromInteger n = Coord n n