Data.Functor.Identity

Copyright	(c) Andy Gill 2001 (c) Oregon Graduate Institute of Science and Technology 2001
License	BSD-style (see the file LICENSE)
Maintainer	ross@soi.city.ac.uk
Stability	stable
Portability	portable
Safe Haskell	Safe
Language	Haskell2010

Description

The identity functor and monad.

This trivial type constructor serves two purposes:

It can be used with functions parameterized by functor or monad classes.
It can be used as a base monad to which a series of monad transformers may be applied to construct a composite monad. Most monad transformer modules include the special case of applying the transformer to Identity. For example, State s is an abbreviation for StateT s Identity.

Since: base-4.8.0.0

newtype Identity a Source

Identity functor and monad. (a non-strict monad)

Examples

Expand

>>> fmap (+1) (Identity 0)
Identity 1

>>> Identity [1, 2, 3] <> Identity [4, 5, 6]
Identity [1,2,3,4,5,6]

>>> do
      x <- Identity 10
      y <- Identity (x + 5)
      pure (x + y)
Identity 25

Since: base-4.8.0.0

Constructors

Identity
Fields runIdentity :: a

Instances

Instances details

Foldable1 Identity Source

Since: base-4.18.0.0

Instance details

Defined in Data.Foldable1

Methods

fold1 :: Semigroup m => Identity m -> m Source

foldMap1 :: Semigroup m => (a -> m) -> Identity a -> m Source

foldMap1' :: Semigroup m => (a -> m) -> Identity a -> m Source

toNonEmpty :: Identity a -> NonEmpty a Source

maximum :: Ord a => Identity a -> a Source

minimum :: Ord a => Identity a -> a Source

head :: Identity a -> a Source

last :: Identity a -> a Source

foldrMap1 :: (a -> b) -> (a -> b -> b) -> Identity a -> b Source

foldlMap1' :: (a -> b) -> (b -> a -> b) -> Identity a -> b Source

foldlMap1 :: (a -> b) -> (b -> a -> b) -> Identity a -> b Source

foldrMap1' :: (a -> b) -> (a -> b -> b) -> Identity a -> b Source

Eq1 Identity Source

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftEq :: (a -> b -> Bool) -> Identity a -> Identity b -> Bool Source

Ord1 Identity Source

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftCompare :: (a -> b -> Ordering) -> Identity a -> Identity b -> Ordering Source

Read1 Identity Source

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (Identity a) Source

liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [Identity a] Source

liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec (Identity a) Source

liftReadListPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec [Identity a] Source

Show1 Identity Source

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftShowsPrec :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> Int -> Identity a -> ShowS Source

liftShowList :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> [Identity a] -> ShowS Source

Applicative Identity Source

Since: base-4.8.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Identity

Methods

pure :: a -> Identity a Source

(<*>) :: Identity (a -> b) -> Identity a -> Identity b Source

liftA2 :: (a -> b -> c) -> Identity a -> Identity b -> Identity c Source

(*>) :: Identity a -> Identity b -> Identity b Source

(<*) :: Identity a -> Identity b -> Identity a Source

Functor Identity Source

Since: base-4.8.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Identity

Methods

fmap :: (a -> b) -> Identity a -> Identity b Source

(<$) :: a -> Identity b -> Identity a Source

Monad Identity Source

Since: base-4.8.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Identity

Methods

(>>=) :: Identity a -> (a -> Identity b) -> Identity b Source

(>>) :: Identity a -> Identity b -> Identity b Source

return :: a -> Identity a Source

MonadFix Identity Source

Since: base-4.8.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Identity

Methods

mfix :: (a -> Identity a) -> Identity a Source

MonadZip Identity Source

Since: ghc-internal-4.8.0.0

Instance details

Defined in GHC.Internal.Control.Monad.Zip

Methods

mzip :: Identity a -> Identity b -> Identity (a, b) Source

mzipWith :: (a -> b -> c) -> Identity a -> Identity b -> Identity c Source

munzip :: Identity (a, b) -> (Identity a, Identity b) Source

Foldable Identity Source

Since: base-4.8.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Identity

Methods

fold :: Monoid m => Identity m -> m Source

foldMap :: Monoid m => (a -> m) -> Identity a -> m Source

foldMap' :: Monoid m => (a -> m) -> Identity a -> m Source

foldr :: (a -> b -> b) -> b -> Identity a -> b Source

foldr' :: (a -> b -> b) -> b -> Identity a -> b Source

foldl :: (b -> a -> b) -> b -> Identity a -> b Source

foldl' :: (b -> a -> b) -> b -> Identity a -> b Source

foldr1 :: (a -> a -> a) -> Identity a -> a Source

foldl1 :: (a -> a -> a) -> Identity a -> a Source

toList :: Identity a -> [a] Source

null :: Identity a -> Bool Source

length :: Identity a -> Int Source

elem :: Eq a => a -> Identity a -> Bool Source

maximum :: Ord a => Identity a -> a Source

minimum :: Ord a => Identity a -> a Source

sum :: Num a => Identity a -> a Source

product :: Num a => Identity a -> a Source

Traversable Identity Source

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Data.Traversable

Methods

traverse :: Applicative f => (a -> f b) -> Identity a -> f (Identity b) Source

sequenceA :: Applicative f => Identity (f a) -> f (Identity a) Source

mapM :: Monad m => (a -> m b) -> Identity a -> m (Identity b) Source

sequence :: Monad m => Identity (m a) -> m (Identity a) Source

Generic1 Identity Source

Instance details

Defined in GHC.Internal.Data.Functor.Identity

Associated Types

type Rep1 Identity	Since: base-4.8.0.0
Instance details Defined in GHC.Internal.Data.Functor.Identity type Rep1 Identity = D1 ('MetaData "Identity" "GHC.Internal.Data.Functor.Identity" "ghc-internal" 'True) (C1 ('MetaCons "Identity" 'PrefixI 'True) (S1 ('MetaSel ('Just "runIdentity") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) Par1))

Methods

from1 :: Identity a -> Rep1 Identity a Source

to1 :: Rep1 Identity a -> Identity a Source

Monoid a => Monoid (Identity a) Source

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Identity

Methods

mempty :: Identity a Source

mappend :: Identity a -> Identity a -> Identity a Source

mconcat :: [Identity a] -> Identity a Source

Semigroup a => Semigroup (Identity a) Source

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Identity

Methods

(<>) :: Identity a -> Identity a -> Identity a Source

sconcat :: NonEmpty (Identity a) -> Identity a Source

stimes :: Integral b => b -> Identity a -> Identity a Source

Bits a => Bits (Identity a) Source

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Identity

Methods

(.&.) :: Identity a -> Identity a -> Identity a Source

(.|.) :: Identity a -> Identity a -> Identity a Source

xor :: Identity a -> Identity a -> Identity a Source

complement :: Identity a -> Identity a Source

shift :: Identity a -> Int -> Identity a Source

rotate :: Identity a -> Int -> Identity a Source

zeroBits :: Identity a Source

bit :: Int -> Identity a Source

setBit :: Identity a -> Int -> Identity a Source

clearBit :: Identity a -> Int -> Identity a Source

complementBit :: Identity a -> Int -> Identity a Source

testBit :: Identity a -> Int -> Bool Source

bitSizeMaybe :: Identity a -> Maybe Int Source

bitSize :: Identity a -> Int Source

isSigned :: Identity a -> Bool Source

shiftL :: Identity a -> Int -> Identity a Source

unsafeShiftL :: Identity a -> Int -> Identity a Source

shiftR :: Identity a -> Int -> Identity a Source

unsafeShiftR :: Identity a -> Int -> Identity a Source

rotateL :: Identity a -> Int -> Identity a Source

rotateR :: Identity a -> Int -> Identity a Source

popCount :: Identity a -> Int Source

FiniteBits a => FiniteBits (Identity a) Source

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Identity

Methods

finiteBitSize :: Identity a -> Int Source

countLeadingZeros :: Identity a -> Int Source

countTrailingZeros :: Identity a -> Int Source

Eq a => Eq (Identity a) Source

Since: base-4.8.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Identity

Methods

(==) :: Identity a -> Identity a -> Bool Source

(/=) :: Identity a -> Identity a -> Bool Source

Ord a => Ord (Identity a) Source

Since: base-4.8.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Identity

Methods

compare :: Identity a -> Identity a -> Ordering Source

(<) :: Identity a -> Identity a -> Bool Source

(<=) :: Identity a -> Identity a -> Bool Source

(>) :: Identity a -> Identity a -> Bool Source

(>=) :: Identity a -> Identity a -> Bool Source

max :: Identity a -> Identity a -> Identity a Source

min :: Identity a -> Identity a -> Identity a Source

Data a => Data (Identity a) Source

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Data.Data

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Identity a -> c (Identity a) Source

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Identity a) Source

toConstr :: Identity a -> Constr Source

dataTypeOf :: Identity a -> DataType Source

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Identity a)) Source

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Identity a)) Source

gmapT :: (forall b. Data b => b -> b) -> Identity a -> Identity a Source

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Identity a -> r Source

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Identity a -> r Source

gmapQ :: (forall d. Data d => d -> u) -> Identity a -> [u] Source

gmapQi :: Int -> (forall d. Data d => d -> u) -> Identity a -> u Source

gmapM :: Monad m => (forall d. Data d => d -> m d) -> Identity a -> m (Identity a) Source

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Identity a -> m (Identity a) Source

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Identity a -> m (Identity a) Source

IsString a => IsString (Identity a) Source

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Data.String

Methods

fromString :: String -> Identity a Source

Bounded a => Bounded (Identity a) Source

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Identity

Methods

minBound :: Identity a Source

maxBound :: Identity a Source

Enum a => Enum (Identity a) Source

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Identity

Methods

succ :: Identity a -> Identity a Source

pred :: Identity a -> Identity a Source

toEnum :: Int -> Identity a Source

fromEnum :: Identity a -> Int Source

enumFrom :: Identity a -> [Identity a] Source

enumFromThen :: Identity a -> Identity a -> [Identity a] Source

enumFromTo :: Identity a -> Identity a -> [Identity a] Source

enumFromThenTo :: Identity a -> Identity a -> Identity a -> [Identity a] Source

Floating a => Floating (Identity a) Source

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Identity

Methods

pi :: Identity a Source

exp :: Identity a -> Identity a Source

log :: Identity a -> Identity a Source

sqrt :: Identity a -> Identity a Source

(**) :: Identity a -> Identity a -> Identity a Source

logBase :: Identity a -> Identity a -> Identity a Source

sin :: Identity a -> Identity a Source

cos :: Identity a -> Identity a Source

tan :: Identity a -> Identity a Source

asin :: Identity a -> Identity a Source

acos :: Identity a -> Identity a Source

atan :: Identity a -> Identity a Source

sinh :: Identity a -> Identity a Source

cosh :: Identity a -> Identity a Source

tanh :: Identity a -> Identity a Source

asinh :: Identity a -> Identity a Source

acosh :: Identity a -> Identity a Source

atanh :: Identity a -> Identity a Source

log1p :: Identity a -> Identity a Source

expm1 :: Identity a -> Identity a Source

log1pexp :: Identity a -> Identity a Source

log1mexp :: Identity a -> Identity a Source

RealFloat a => RealFloat (Identity a) Source

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Identity

Methods

floatRadix :: Identity a -> Integer Source

floatDigits :: Identity a -> Int Source

floatRange :: Identity a -> (Int, Int) Source

decodeFloat :: Identity a -> (Integer, Int) Source

encodeFloat :: Integer -> Int -> Identity a Source

exponent :: Identity a -> Int Source

significand :: Identity a -> Identity a Source

scaleFloat :: Int -> Identity a -> Identity a Source

isNaN :: Identity a -> Bool Source

isInfinite :: Identity a -> Bool Source

isDenormalized :: Identity a -> Bool Source

isNegativeZero :: Identity a -> Bool Source

isIEEE :: Identity a -> Bool Source

atan2 :: Identity a -> Identity a -> Identity a Source

Storable a => Storable (Identity a) Source

Since: base-4.9.0.0

Instance details

Defined in GHC.Internal.Data.Functor.Identity

Methods

sizeOf :: Identity a -> Int Source

alignment :: Identity a -> Int Source

peekElemOff :: Ptr (Identity a) -> Int -> IO (Identity a) Source

pokeElemOff :: Ptr (Identity a) -> Int -> Identity a -> IO () Source

peekByteOff :: Ptr b -> Int -> IO (Identity a) Source

pokeByteOff :: Ptr b -> Int -> Identity a -> IO () Source

peek :: Ptr (Identity a) -> IO (Identity a) Source

poke :: Ptr (Identity a) -> Identity a -> IO () Source

Generic (Identity a) Source

Instance details

Defined in GHC.Internal.Data.Functor.Identity

Associated Types

type Rep (Identity a)	Since: base-4.8.0.0
Instance details Defined in GHC.Internal.Data.Functor.Identity type Rep (Identity a) = D1 ('MetaData "Identity" "GHC.Internal.Data.Functor.Identity" "ghc-internal" 'True) (C1 ('MetaCons "Identity" 'PrefixI 'True) (S1 ('MetaSel ('Just "runIdentity") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a)))