{-# LANGUAGE DeriveDataTypeable #-} {-# LANGUAGE DeriveGeneric #-} {-# LANGUAGE PolyKinds #-} {-# LANGUAGE Safe #-} ----------------------------------------------------------------------------- -- | -- Module : Data.Functor.Product -- Copyright : (c) Ross Paterson 2010 -- License : BSD-style (see the file LICENSE) -- -- Maintainer : libraries@haskell.org -- Stability : experimental -- Portability : portable -- -- Products, lifted to functors. -- -- @since 4.9.0.0 ----------------------------------------------------------------------------- module Data.Functor.Product ( Product(..), ) where import Control.Applicative import Control.Monad (MonadPlus(..)) import Control.Monad.Fix (MonadFix(..)) import Control.Monad.Zip (MonadZip(mzipWith)) import Data.Data (Data) import Data.Functor.Classes import GHC.Generics (Generic, Generic1) import Text.Read (Read(..), readListDefault, readListPrecDefault) -- | Lifted product of functors. data Product f g a = Pair (f a) (g a) deriving ( Data -- ^ @since 4.9.0.0 , Generic -- ^ @since 4.9.0.0 , Generic1 -- ^ @since 4.9.0.0 ) -- | @since 4.9.0.0 instance (Eq1 f, Eq1 g) => Eq1 (Product f g) where liftEq eq (Pair x1 y1) (Pair x2 y2) = liftEq eq x1 x2 && liftEq eq y1 y2 -- | @since 4.9.0.0 instance (Ord1 f, Ord1 g) => Ord1 (Product f g) where liftCompare comp (Pair x1 y1) (Pair x2 y2) = liftCompare comp x1 x2 `mappend` liftCompare comp y1 y2 -- | @since 4.9.0.0 instance (Read1 f, Read1 g) => Read1 (Product f g) where liftReadPrec rp rl = readData $ readBinaryWith (liftReadPrec rp rl) (liftReadPrec rp rl) "Pair" Pair liftReadListPrec = liftReadListPrecDefault liftReadList = liftReadListDefault -- | @since 4.9.0.0 instance (Show1 f, Show1 g) => Show1 (Product f g) where liftShowsPrec sp sl d (Pair x y) = showsBinaryWith (liftShowsPrec sp sl) (liftShowsPrec sp sl) "Pair" d x y -- | @since 4.9.0.0 instance (Eq1 f, Eq1 g, Eq a) => Eq (Product f g a) where (==) = eq1 -- | @since 4.9.0.0 instance (Ord1 f, Ord1 g, Ord a) => Ord (Product f g a) where compare = compare1 -- | @since 4.9.0.0 instance (Read1 f, Read1 g, Read a) => Read (Product f g a) where readPrec = readPrec1 readListPrec = readListPrecDefault readList = readListDefault -- | @since 4.9.0.0 instance (Show1 f, Show1 g, Show a) => Show (Product f g a) where showsPrec = showsPrec1 -- | @since 4.9.0.0 instance (Functor f, Functor g) => Functor (Product f g) where fmap f (Pair x y) = Pair (fmap f x) (fmap f y) a <$ (Pair x y) = Pair (a <$ x) (a <$ y) -- | @since 4.9.0.0 instance (Foldable f, Foldable g) => Foldable (Product f g) where foldMap f (Pair x y) = foldMap f x `mappend` foldMap f y -- | @since 4.9.0.0 instance (Traversable f, Traversable g) => Traversable (Product f g) where traverse f (Pair x y) = liftA2 Pair (traverse f x) (traverse f y) -- | @since 4.9.0.0 instance (Applicative f, Applicative g) => Applicative (Product f g) where pure x = Pair (pure x) (pure x) Pair f g <*> Pair x y = Pair (f <*> x) (g <*> y) liftA2 f (Pair a b) (Pair x y) = Pair (liftA2 f a x) (liftA2 f b y) -- | @since 4.9.0.0 instance (Alternative f, Alternative g) => Alternative (Product f g) where empty = Pair empty empty Pair x1 y1 <|> Pair x2 y2 = Pair (x1 <|> x2) (y1 <|> y2) -- | @since 4.9.0.0 instance (Monad f, Monad g) => Monad (Product f g) where Pair m n >>= f = Pair (m >>= fstP . f) (n >>= sndP . f) where fstP (Pair a _) = a sndP (Pair _ b) = b -- | @since 4.9.0.0 instance (MonadPlus f, MonadPlus g) => MonadPlus (Product f g) where mzero = Pair mzero mzero Pair x1 y1 `mplus` Pair x2 y2 = Pair (x1 `mplus` x2) (y1 `mplus` y2) -- | @since 4.9.0.0 instance (MonadFix f, MonadFix g) => MonadFix (Product f g) where mfix f = Pair (mfix (fstP . f)) (mfix (sndP . f)) where fstP (Pair a _) = a sndP (Pair _ b) = b -- | @since 4.9.0.0 instance (MonadZip f, MonadZip g) => MonadZip (Product f g) where mzipWith f (Pair x1 y1) (Pair x2 y2) = Pair (mzipWith f x1 x2) (mzipWith f y1 y2) -- | @since 4.16.0.0 instance (Semigroup (f a), Semigroup (g a)) => Semigroup (Product f g a) where Pair x1 y1 <> Pair x2 y2 = Pair (x1 <> x2) (y1 <> y2) -- | @since 4.16.0.0 instance (Monoid (f a), Monoid (g a)) => Monoid (Product f g a) where mempty = Pair mempty mempty