ref: a4229eb282ca32bc14103a33092e94382c3c7ca0
dir: /lib/Data/Functor/Sum.hs/
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE Safe #-}
{-# LANGUAGE StandaloneDeriving #-}
-----------------------------------------------------------------------------
-- |
-- Module : Data.Functor.Sum
-- Copyright : (c) Ross Paterson 2014
-- License : BSD-style (see the file LICENSE)
--
-- Maintainer : libraries@haskell.org
-- Stability : stable
-- Portability : portable
--
-- Sums, lifted to functors.
--
-- @since 4.9.0.0
-----------------------------------------------------------------------------
module Data.Functor.Sum (
Sum(..),
) where
import Control.Applicative ((<|>))
--import Data.Data (Data)
import Data.Foldable
import Data.Functor.Classes
import Data.Traversable
--import GHC.Generics (Generic, Generic1)
-- | Lifted sum of functors.
--
-- ==== __Examples__
--
-- >>> fmap (+1) (InL (Just 1)) :: Sum Maybe [] Int
-- InL (Just 2)
--
-- >>> fmap (+1) (InR [1, 2, 3]) :: Sum Maybe [] Int
-- InR [2,3,4]
data Sum f g a = InL (f a) | InR (g a)
{-
deriving ( Data -- ^ @since 4.9.0.0
, Generic -- ^ @since 4.9.0.0
, Generic1 -- ^ @since 4.9.0.0
)
-- | @since 4.18.0.0
deriving instance (Eq (f a), Eq (g a)) => Eq (Sum f g a)
-- | @since 4.18.0.0
deriving instance (Ord (f a), Ord (g a)) => Ord (Sum f g a)
-- | @since 4.18.0.0
deriving instance (Read (f a), Read (g a)) => Read (Sum f g a)
-- | @since 4.18.0.0
deriving instance (Show (f a), Show (g a)) => Show (Sum f g a)
-}
-- | @since 4.9.0.0
instance (Eq1 f, Eq1 g) => Eq1 (Sum f g) where
liftEq eq (InL x1) (InL x2) = liftEq eq x1 x2
liftEq _ (InL _) (InR _) = False
liftEq _ (InR _) (InL _) = False
liftEq eq (InR y1) (InR y2) = liftEq eq y1 y2
-- | @since 4.9.0.0
instance (Ord1 f, Ord1 g) => Ord1 (Sum f g) where
liftCompare comp (InL x1) (InL x2) = liftCompare comp x1 x2
liftCompare _ (InL _) (InR _) = LT
liftCompare _ (InR _) (InL _) = GT
liftCompare comp (InR y1) (InR y2) = liftCompare comp y1 y2
-- | @since 4.9.0.0
instance (Read1 f, Read1 g) => Read1 (Sum f g) where
liftReadPrec rp rl = readData $
readUnaryWith (liftReadPrec rp rl) "InL" InL <|>
readUnaryWith (liftReadPrec rp rl) "InR" InR
liftReadListPrec = liftReadListPrecDefault
liftReadList = liftReadListDefault
-- | @since 4.9.0.0
instance (Show1 f, Show1 g) => Show1 (Sum f g) where
liftShowsPrec sp sl d (InL x) =
showsUnaryWith (liftShowsPrec sp sl) "InL" d x
liftShowsPrec sp sl d (InR y) =
showsUnaryWith (liftShowsPrec sp sl) "InR" d y
-- | @since 4.9.0.0
instance (Functor f, Functor g) => Functor (Sum f g) where
fmap f (InL x) = InL (fmap f x)
fmap f (InR y) = InR (fmap f y)
a <$ (InL x) = InL (a <$ x)
a <$ (InR y) = InR (a <$ y)
-- | @since 4.9.0.0
instance (Foldable f, Foldable g) => Foldable (Sum f g) where
foldMap f (InL x) = foldMap f x
foldMap f (InR y) = foldMap f y
-- | @since 4.9.0.0
instance (Traversable f, Traversable g) => Traversable (Sum f g) where
traverse f (InL x) = InL <$> traverse f x
traverse f (InR y) = InR <$> traverse f y