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

Data.Functor.Identity

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

Synopsis

newtype Identity a = Identity {
- runIdentity :: a
}

Documentation

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)))