{-# LANGUAGE DeriveGeneric #-}{-# LANGUAGE GeneralizedNewtypeDeriving #-}{-# LANGUAGE NoImplicitPrelude #-}{-# LANGUAGE PolyKinds #-}{-# LANGUAGE ScopedTypeVariables #-}{-# LANGUAGE Trustworthy #-}------------------------------------------------------------------------------- |-- Module : Data.Functor.Const-- Copyright : Conor McBride and Ross Paterson 2005-- License : BSD-style (see the LICENSE file in the distribution)---- Maintainer : libraries@haskell.org-- Stability : experimental-- Portability : portable-- The 'Const' functor.---- @since 4.9.0.0moduleData.Functor.Const(Const (..))whereimportData.Bits (Bits ,FiniteBits )importData.Foldable (Foldable (foldMap ))importForeign.Storable (Storable )importGHC.Arr (Ix )importGHC.Base importGHC.Enum (Bounded ,Enum )importGHC.Float (Floating ,RealFloat )importGHC.Generics (Generic ,Generic1 )importGHC.Num (Num )importGHC.Real (Fractional ,Integral ,Real ,RealFrac )importGHC.Read (Read (readsPrec ),readParen ,lex )importGHC.Show (Show (showsPrec ),showParen ,showString )-- | The 'Const' functor.newtypeConst a b =Const {Const a b -> a
getConst ::a }deriving(Bits -- ^ @since 4.9.0.0,Bounded -- ^ @since 4.9.0.0,Enum -- ^ @since 4.9.0.0,Eq-- ^ @since 4.9.0.0,FiniteBits -- ^ @since 4.9.0.0,Floating -- ^ @since 4.9.0.0,Fractional -- ^ @since 4.9.0.0,Generic -- ^ @since 4.9.0.0,Generic1 -- ^ @since 4.9.0.0,Integral -- ^ @since 4.9.0.0,Ix -- ^ @since 4.9.0.0,Semigroup -- ^ @since 4.9.0.0,Monoid -- ^ @since 4.9.0.0,Num -- ^ @since 4.9.0.0,Ord-- ^ @since 4.9.0.0,Real -- ^ @since 4.9.0.0,RealFrac -- ^ @since 4.9.0.0,RealFloat -- ^ @since 4.9.0.0,Storable -- ^ @since 4.9.0.0)-- | This instance would be equivalent to the derived instances of the-- 'Const' newtype if the 'getConst' field were removed---- @since 4.8.0.0instanceRead a =>Read (Const a b )wherereadsPrec :: Int -> ReadS (Const a b)
readsPrec d :: Int
d =Bool -> ReadS (Const a b) -> ReadS (Const a b)
forall a. Bool -> ReadS a -> ReadS a
readParen (Int
d Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
>10)(ReadS (Const a b) -> ReadS (Const a b))
-> ReadS (Const a b) -> ReadS (Const a b)
forall a b. (a -> b) -> a -> b
$ \r :: String
r ->[(a -> Const a b
forall k a (b :: k). a -> Const a b
Const a
x ,String
t )|("Const",s :: String
s )<-ReadS String
lex String
r ,(x :: a
x ,t :: String
t )<-Int -> ReadS a
forall a. Read a => Int -> ReadS a
readsPrec 11String
s ]-- | This instance would be equivalent to the derived instances of the-- 'Const' newtype if the 'getConst' field were removed---- @since 4.8.0.0instanceShow a =>Show (Const a b )whereshowsPrec :: Int -> Const a b -> ShowS
showsPrec d :: Int
d (Const x :: a
x )=Bool -> ShowS -> ShowS
showParen (Int
d Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
>10)(ShowS -> ShowS) -> ShowS -> ShowS
forall a b. (a -> b) -> a -> b
$ String -> ShowS
showString "Const "ShowS -> ShowS -> ShowS
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Int -> a -> ShowS
forall a. Show a => Int -> a -> ShowS
showsPrec 11a
x -- | @since 4.7.0.0instanceFoldable (Const m )wherefoldMap :: (a -> m) -> Const m a -> m
foldMap __=m
forall a. Monoid a => a
mempty -- | @since 2.01instanceFunctor (Const m )wherefmap :: (a -> b) -> Const m a -> Const m b
fmap _(Const v :: m
v )=m -> Const m b
forall k a (b :: k). a -> Const a b
Const m
v -- | @since 2.0.1instanceMonoid m =>Applicative (Const m )wherepure :: a -> Const m a
pure _=m -> Const m a
forall k a (b :: k). a -> Const a b
Const m
forall a. Monoid a => a
mempty liftA2 :: (a -> b -> c) -> Const m a -> Const m b -> Const m c
liftA2 _(Const x :: m
x )(Const y :: m
y )=m -> Const m c
forall k a (b :: k). a -> Const a b
Const (m
x m -> m -> m
forall a. Monoid a => a -> a -> a
`mappend` m
y )<*> :: Const m (a -> b) -> Const m a -> Const m b
(<*>) =(m -> m -> m) -> Const m (a -> b) -> Const m a -> Const m b
forall a b. Coercible a b => a -> b
coerce(m -> m -> m
forall a. Monoid a => a -> a -> a
mappend ::m ->m ->m )-- This is pretty much the same as-- Const f <*> Const v = Const (f `mappend` v)-- but guarantees that mappend for Const a b will have the same arity-- as the one for a; it won't create a closure to raise the arity-- to 2.