module Data.Bifunctor (Bifunctor(..)) where
import Control.Applicative
class Bifunctor p where
bimap :: (a -> b) -> (c -> d) -> p a c -> p b d
bimap f g = first f . second g
first :: (a -> b) -> p a c -> p b c
first f = bimap f id
second :: (b -> c) -> p a b -> p a c
second = bimap id
instance Bifunctor (,) where
bimap f g (a, b) = (f a, g b)
instance Bifunctor ((,,) x) where
bimap f g (x, a, b) = (x, f a, g b)
instance Bifunctor ((,,,) x y) where
bimap f g (x, y, a, b) = (x, y, f a, g b)
instance Bifunctor ((,,,,) x y z) where
bimap f g (x, y, z, a, b) = (x, y, z, f a, g b)
instance Bifunctor Either where
bimap f _ (Left a) = Left (f a)
bimap _ g (Right b) = Right (g b)
instance Bifunctor Const where
bimap f _ (Const a) = Const (f a)