Safe Haskell	Safe
Language	Haskell98

Lens.Family.State.Lazy

Contents

Compound Assignments
Strict Assignments
Types
Re-exports

Description

Lenses allow you to use fields of the state of a state monad as if they were variables in an imperative language. use is used to retrieve the value of a variable, and .= and %= allow you to set and modify a variable. C-style compound assignments are also provided.

Synopsis

zoom :: Monad m => LensLike' (Zooming m c) s a -> StateT a m c -> StateT s m c
use :: Monad m => FoldLike a s t a b -> StateT s m a
uses :: Monad m => FoldLike r s t a b -> (a -> r) -> StateT s m r
(%=) :: Monad m => ASetter s s a b -> (a -> b) -> StateT s m ()
assign :: Monad m => ASetter s s a b -> b -> StateT s m ()
(.=) :: Monad m => ASetter s s a b -> b -> StateT s m ()
(%%=) :: Monad m => LensLike (Writer c) s s a b -> (a -> (c, b)) -> StateT s m c
(<~) :: Monad m => ASetter s s a b -> StateT s m b -> StateT s m ()
(+=) :: (Monad m, Num a) => ASetter' s a -> a -> StateT s m ()
(-=) :: (Monad m, Num a) => ASetter' s a -> a -> StateT s m ()
(*=) :: (Monad m, Num a) => ASetter' s a -> a -> StateT s m ()
(//=) :: (Monad m, Fractional a) => ASetter' s a -> a -> StateT s m ()
(&&=) :: Monad m => ASetter' s Bool -> Bool -> StateT s m ()
(||=) :: Monad m => ASetter' s Bool -> Bool -> StateT s m ()
(<>=) :: (Monad m, Monoid a) => ASetter' s a -> a -> StateT s m ()
(%!=) :: Monad m => ASetter s s a b -> (a -> b) -> StateT s m ()
(+!=) :: (Monad m, Num a) => ASetter' s a -> a -> StateT s m ()
(-!=) :: (Monad m, Num a) => ASetter' s a -> a -> StateT s m ()
(*!=) :: (Monad m, Num a) => ASetter' s a -> a -> StateT s m ()
(//!=) :: (Monad m, Fractional a) => ASetter' s a -> a -> StateT s m ()
(&&!=) :: Monad m => ASetter' s Bool -> Bool -> StateT s m ()
(||!=) :: Monad m => ASetter' s Bool -> Bool -> StateT s m ()
(<>!=) :: (Monad m, Monoid a) => ASetter' s a -> a -> StateT s m ()
data Zooming m c a
type LensLike f s t a b = (a -> f b) -> s -> f t
type LensLike' f s a = (a -> f a) -> s -> f s
type FoldLike r s t a b = LensLike (Constant r) s t a b
data Constant a (b :: k) :: forall k. Type -> k -> Type
type ASetter s t a b = LensLike Identity s t a b
type ASetter' s a = LensLike' Identity s a
data Identity a
data StateT s (m :: Type -> Type) a
type Writer w = WriterT w Identity

Documentation

zoom :: Monad m => LensLike' (Zooming m c) s a -> StateT a m c -> StateT s m c Source #

zoom :: Monad m => Lens' s a -> StateT a m c -> StateT s m c

Lift a stateful operation on a field to a stateful operation on the whole state. This is a good way to call a "subroutine" that only needs access to part of the state.

zoom :: (Monad m, Monoid c) => Traversal' s a -> StateT a m c -> StateT s m c

Run the "subroutine" on each element of the traversal in turn and mconcat all the results together.

zoom :: Monad m => Traversal' s a -> StateT a m () -> StateT s m ()

Run the "subroutine" on each element the traversal in turn.

use :: Monad m => FoldLike a s t a b -> StateT s m a Source #

use :: Monad m => Getter s t a b -> StateT s m a

Retrieve a field of the state

use :: (Monad m, Monoid a) => Fold s t a b -> StateT s m a

Retrieve a monoidal summary of all the referenced fields from the state

uses :: Monad m => FoldLike r s t a b -> (a -> r) -> StateT s m r Source #

uses :: (Monad m, Monoid r) => Fold s t a b -> (a -> r) -> StateT s m r

Retrieve all the referenced fields from the state and foldMap the results together with f :: a -> r.

uses :: Monad m => Getter s t a b -> (a -> r) -> StateT s m r

Retrieve a field of the state and pass it through the function f :: a -> r.

uses l f = f <$> use l

(%=) :: Monad m => ASetter s s a b -> (a -> b) -> StateT s m () infix 4 Source #

Modify a field of the state.

assign :: Monad m => ASetter s s a b -> b -> StateT s m () Source #

Set a field of the state.

(.=) :: Monad m => ASetter s s a b -> b -> StateT s m () infix 4 Source #

Set a field of the state.

(%%=) :: Monad m => LensLike (Writer c) s s a b -> (a -> (c, b)) -> StateT s m c infix 4 Source #

(%%=) :: Monad m => Lens s s a b -> (a -> (c, b)) -> StateT s m c

Modify a field of the state while returning another value.

(%%=) :: (Monad m, Monoid c) => Traversal s s a b -> (a -> (c, b)) -> StateT s m c

Modify each field of the state and return the mconcat of the other values.

(<~) :: Monad m => ASetter s s a b -> StateT s m b -> StateT s m () infixr 2 Source #

Set a field of the state using the result of executing a stateful command.

Compound Assignments

(+=) :: (Monad m, Num a) => ASetter' s a -> a -> StateT s m () infixr 4 Source #

(-=) :: (Monad m, Num a) => ASetter' s a -> a -> StateT s m () infixr 4 Source #

(*=) :: (Monad m, Num a) => ASetter' s a -> a -> StateT s m () infixr 4 Source #

(//=) :: (Monad m, Fractional a) => ASetter' s a -> a -> StateT s m () infixr 4 Source #

(&&=) :: Monad m => ASetter' s Bool -> Bool -> StateT s m () infixr 4 Source #

(||=) :: Monad m => ASetter' s Bool -> Bool -> StateT s m () infixr 4 Source #

(<>=) :: (Monad m, Monoid a) => ASetter' s a -> a -> StateT s m () infixr 4 Source #

Monoidally append a value to all referenced fields of the state.

Strict Assignments

(%!=) :: Monad m => ASetter s s a b -> (a -> b) -> StateT s m () infix 4 Source #

Strictly modify a field of the state.

(+!=) :: (Monad m, Num a) => ASetter' s a -> a -> StateT s m () infixr 4 Source #

(-!=) :: (Monad m, Num a) => ASetter' s a -> a -> StateT s m () infixr 4 Source #

(*!=) :: (Monad m, Num a) => ASetter' s a -> a -> StateT s m () infixr 4 Source #

(//!=) :: (Monad m, Fractional a) => ASetter' s a -> a -> StateT s m () infixr 4 Source #

(&&!=) :: Monad m => ASetter' s Bool -> Bool -> StateT s m () infixr 4 Source #

(||!=) :: Monad m => ASetter' s Bool -> Bool -> StateT s m () infixr 4 Source #

(<>!=) :: (Monad m, Monoid a) => ASetter' s a -> a -> StateT s m () infixr 4 Source #

Types

data Zooming m c a Source #

Instances

Monad m => Functor (Zooming m c) Source #
Instance details Defined in Lens.Family.State.Zoom Methods fmap :: (a -> b) -> Zooming m c a -> Zooming m c b # (<$) :: a -> Zooming m c b -> Zooming m c a #
(Monoid c, Monad m) => Applicative (Zooming m c) Source #
Instance details Defined in Lens.Family.State.Zoom Methods pure :: a -> Zooming m c a # (<>) :: Zooming m c (a -> b) -> Zooming m c a -> Zooming m c b # liftA2 :: (a -> b -> c0) -> Zooming m c a -> Zooming m c b -> Zooming m c c0 # (>) :: Zooming m c a -> Zooming m c b -> Zooming m c b # (<*) :: Zooming m c a -> Zooming m c b -> Zooming m c a #

Re-exports

type LensLike f s t a b = (a -> f b) -> s -> f t Source #

type LensLike' f s a = (a -> f a) -> s -> f s Source #

type FoldLike r s t a b = LensLike (Constant r) s t a b Source #

data Constant a (b :: k) :: forall k. Type -> k -> Type #

Constant functor.

Instances

Bitraversable (Constant :: Type -> Type -> Type)
Instance details Defined in Data.Functor.Constant Methods bitraverse :: Applicative f => (a -> f c) -> (b -> f d) -> Constant a b -> f (Constant c d) #
Bifoldable (Constant :: Type -> Type -> Type)
Instance details Defined in Data.Functor.Constant Methods bifold :: Monoid m => Constant m m -> m # bifoldMap :: Monoid m => (a -> m) -> (b -> m) -> Constant a b -> m # bifoldr :: (a -> c -> c) -> (b -> c -> c) -> c -> Constant a b -> c # bifoldl :: (c -> a -> c) -> (c -> b -> c) -> c -> Constant a b -> c #
Bifunctor (Constant :: Type -> Type -> Type)
Instance details Defined in Data.Functor.Constant Methods bimap :: (a -> b) -> (c -> d) -> Constant a c -> Constant b d # first :: (a -> b) -> Constant a c -> Constant b c # second :: (b -> c) -> Constant a b -> Constant a c #
Eq2 (Constant :: Type -> Type -> Type)
Instance details Defined in Data.Functor.Constant Methods liftEq2 :: (a -> b -> Bool) -> (c -> d -> Bool) -> Constant a c -> Constant b d -> Bool #
Ord2 (Constant :: Type -> Type -> Type)
Instance details Defined in Data.Functor.Constant Methods liftCompare2 :: (a -> b -> Ordering) -> (c -> d -> Ordering) -> Constant a c -> Constant b d -> Ordering #
Read2 (Constant :: Type -> Type -> Type)
Instance details Defined in Data.Functor.Constant Methods liftReadsPrec2 :: (Int -> ReadS a) -> ReadS [a] -> (Int -> ReadS b) -> ReadS [b] -> Int -> ReadS (Constant a b) # liftReadList2 :: (Int -> ReadS a) -> ReadS [a] -> (Int -> ReadS b) -> ReadS [b] -> ReadS [Constant a b] # liftReadPrec2 :: ReadPrec a -> ReadPrec [a] -> ReadPrec b -> ReadPrec [b] -> ReadPrec (Constant a b) # liftReadListPrec2 :: ReadPrec a -> ReadPrec [a] -> ReadPrec b -> ReadPrec [b] -> ReadPrec [Constant a b] #
Show2 (Constant :: Type -> Type -> Type)
Instance details Defined in Data.Functor.Constant Methods liftShowsPrec2 :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> (Int -> b -> ShowS) -> ([b] -> ShowS) -> Int -> Constant a b -> ShowS # liftShowList2 :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> (Int -> b -> ShowS) -> ([b] -> ShowS) -> [Constant a b] -> ShowS #
Functor (Constant a :: Type -> Type)
Instance details Defined in Data.Functor.Constant Methods fmap :: (a0 -> b) -> Constant a a0 -> Constant a b # (<$) :: a0 -> Constant a b -> Constant a a0 #
Monoid a => Applicative (Constant a :: Type -> Type)
Instance details Defined in Data.Functor.Constant Methods pure :: a0 -> Constant a a0 # (<>) :: Constant a (a0 -> b) -> Constant a a0 -> Constant a b # liftA2 :: (a0 -> b -> c) -> Constant a a0 -> Constant a b -> Constant a c # (>) :: Constant a a0 -> Constant a b -> Constant a b # (<*) :: Constant a a0 -> Constant a b -> Constant a a0 #
Foldable (Constant a :: Type -> Type)
Instance details Defined in Data.Functor.Constant Methods fold :: Monoid m => Constant a m -> m # foldMap :: Monoid m => (a0 -> m) -> Constant a a0 -> m # foldr :: (a0 -> b -> b) -> b -> Constant a a0 -> b # foldr' :: (a0 -> b -> b) -> b -> Constant a a0 -> b # foldl :: (b -> a0 -> b) -> b -> Constant a a0 -> b # foldl' :: (b -> a0 -> b) -> b -> Constant a a0 -> b # foldr1 :: (a0 -> a0 -> a0) -> Constant a a0 -> a0 # foldl1 :: (a0 -> a0 -> a0) -> Constant a a0 -> a0 # toList :: Constant a a0 -> [a0] # null :: Constant a a0 -> Bool # length :: Constant a a0 -> Int # elem :: Eq a0 => a0 -> Constant a a0 -> Bool # maximum :: Ord a0 => Constant a a0 -> a0 # minimum :: Ord a0 => Constant a a0 -> a0 # sum :: Num a0 => Constant a a0 -> a0 # product :: Num a0 => Constant a a0 -> a0 #
Traversable (Constant a :: Type -> Type)
Instance details Defined in Data.Functor.Constant Methods traverse :: Applicative f => (a0 -> f b) -> Constant a a0 -> f (Constant a b) # sequenceA :: Applicative f => Constant a (f a0) -> f (Constant a a0) # mapM :: Monad m => (a0 -> m b) -> Constant a a0 -> m (Constant a b) # sequence :: Monad m => Constant a (m a0) -> m (Constant a a0) #
Contravariant (Constant a :: Type -> Type)
Instance details Defined in Data.Functor.Constant Methods contramap :: (a0 -> b) -> Constant a b -> Constant a a0 # (>$) :: b -> Constant a b -> Constant a a0 #
Eq a => Eq1 (Constant a :: Type -> Type)
Instance details Defined in Data.Functor.Constant Methods liftEq :: (a0 -> b -> Bool) -> Constant a a0 -> Constant a b -> Bool #
Ord a => Ord1 (Constant a :: Type -> Type)
Instance details Defined in Data.Functor.Constant Methods liftCompare :: (a0 -> b -> Ordering) -> Constant a a0 -> Constant a b -> Ordering #
Read a => Read1 (Constant a :: Type -> Type)
Instance details Defined in Data.Functor.Constant Methods liftReadsPrec :: (Int -> ReadS a0) -> ReadS [a0] -> Int -> ReadS (Constant a a0) # liftReadList :: (Int -> ReadS a0) -> ReadS [a0] -> ReadS [Constant a a0] # liftReadPrec :: ReadPrec a0 -> ReadPrec [a0] -> ReadPrec (Constant a a0) # liftReadListPrec :: ReadPrec a0 -> ReadPrec [a0] -> ReadPrec [Constant a a0] #
Show a => Show1 (Constant a :: Type -> Type)
Instance details Defined in Data.Functor.Constant Methods liftShowsPrec :: (Int -> a0 -> ShowS) -> ([a0] -> ShowS) -> Int -> Constant a a0 -> ShowS # liftShowList :: (Int -> a0 -> ShowS) -> ([a0] -> ShowS) -> [Constant a a0] -> ShowS #
Phantom (Constant a :: Type -> Type) Source #
Instance details Defined in Lens.Family.Phantom Methods coerce :: Constant a a0 -> Constant a b
Eq a => Eq (Constant a b)
Instance details Defined in Data.Functor.Constant Methods (==) :: Constant a b -> Constant a b -> Bool # (/=) :: Constant a b -> Constant a b -> Bool #
Ord a => Ord (Constant a b)
Instance details Defined in Data.Functor.Constant Methods compare :: Constant a b -> Constant a b -> Ordering # (<) :: Constant a b -> Constant a b -> Bool # (<=) :: Constant a b -> Constant a b -> Bool # (>) :: Constant a b -> Constant a b -> Bool # (>=) :: Constant a b -> Constant a b -> Bool # max :: Constant a b -> Constant a b -> Constant a b # min :: Constant a b -> Constant a b -> Constant a b #
Read a => Read (Constant a b)
Instance details Defined in Data.Functor.Constant Methods readsPrec :: Int -> ReadS (Constant a b) # readList :: ReadS [Constant a b] # readPrec :: ReadPrec (Constant a b) # readListPrec :: ReadPrec [Constant a b] #
Show a => Show (Constant a b)
Instance details Defined in Data.Functor.Constant Methods showsPrec :: Int -> Constant a b -> ShowS # show :: Constant a b -> String # showList :: [Constant a b] -> ShowS #
Semigroup a => Semigroup (Constant a b)
Instance details Defined in Data.Functor.Constant Methods (<>) :: Constant a b -> Constant a b -> Constant a b # sconcat :: NonEmpty (Constant a b) -> Constant a b # stimes :: Integral b0 => b0 -> Constant a b -> Constant a b #
Monoid a => Monoid (Constant a b)
Instance details Defined in Data.Functor.Constant Methods mempty :: Constant a b # mappend :: Constant a b -> Constant a b -> Constant a b # mconcat :: [Constant a b] -> Constant a b #

type ASetter s t a b = LensLike Identity s t a b Source #

type ASetter' s a = LensLike' Identity s a Source #

data Identity a #

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

Since: base-4.8.0.0

Instances

Monad Identity	Since: base-4.8.0.0
Instance details Defined in Data.Functor.Identity Methods (>>=) :: Identity a -> (a -> Identity b) -> Identity b # (>>) :: Identity a -> Identity b -> Identity b # return :: a -> Identity a # fail :: String -> Identity a #
Functor Identity	Since: base-4.8.0.0
Instance details Defined in Data.Functor.Identity Methods fmap :: (a -> b) -> Identity a -> Identity b # (<$) :: a -> Identity b -> Identity a #
MonadFix Identity	Since: base-4.8.0.0
Instance details Defined in Data.Functor.Identity Methods mfix :: (a -> Identity a) -> Identity a #
Applicative Identity	Since: base-4.8.0.0
Instance details Defined in Data.Functor.Identity Methods pure :: a -> Identity a # (<>) :: Identity (a -> b) -> Identity a -> Identity b # liftA2 :: (a -> b -> c) -> Identity a -> Identity b -> Identity c # (>) :: Identity a -> Identity b -> Identity b # (<*) :: Identity a -> Identity b -> Identity a #
Foldable Identity	Since: base-4.8.0.0
Instance details Defined in Data.Functor.Identity Methods fold :: Monoid m => Identity m -> m # foldMap :: Monoid m => (a -> m) -> Identity a -> m # foldr :: (a -> b -> b) -> b -> Identity a -> b # foldr' :: (a -> b -> b) -> b -> Identity a -> b # foldl :: (b -> a -> b) -> b -> Identity a -> b # foldl' :: (b -> a -> b) -> b -> Identity a -> b # foldr1 :: (a -> a -> a) -> Identity a -> a # foldl1 :: (a -> a -> a) -> Identity a -> a # toList :: Identity a -> [a] # null :: Identity a -> Bool # length :: Identity a -> Int # elem :: Eq a => a -> Identity a -> Bool # maximum :: Ord a => Identity a -> a # minimum :: Ord a => Identity a -> a # sum :: Num a => Identity a -> a # product :: Num a => Identity a -> a #
Traversable Identity	Since: base-4.9.0.0
Instance details Defined in Data.Traversable Methods traverse :: Applicative f => (a -> f b) -> Identity a -> f (Identity b) # sequenceA :: Applicative f => Identity (f a) -> f (Identity a) # mapM :: Monad m => (a -> m b) -> Identity a -> m (Identity b) # sequence :: Monad m => Identity (m a) -> m (Identity a) #
Eq1 Identity	Since: base-4.9.0.0
Instance details Defined in Data.Functor.Classes Methods liftEq :: (a -> b -> Bool) -> Identity a -> Identity b -> Bool #
Ord1 Identity	Since: base-4.9.0.0
Instance details Defined in Data.Functor.Classes Methods liftCompare :: (a -> b -> Ordering) -> Identity a -> Identity b -> Ordering #
Read1 Identity	Since: base-4.9.0.0
Instance details Defined in Data.Functor.Classes Methods liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (Identity a) # liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [Identity a] # liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec (Identity a) # liftReadListPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec [Identity a] #
Show1 Identity	Since: base-4.9.0.0
Instance details Defined in Data.Functor.Classes Methods liftShowsPrec :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> Int -> Identity a -> ShowS # liftShowList :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> [Identity a] -> ShowS #
Identical Identity Source #
Instance details Defined in Lens.Family.Identical Methods extract :: Identity a -> a
Bounded a => Bounded (Identity a)	Since: base-4.9.0.0
Instance details Defined in Data.Functor.Identity Methods minBound :: Identity a # maxBound :: Identity a #
Enum a => Enum (Identity a)	Since: base-4.9.0.0
Instance details Defined in Data.Functor.Identity Methods succ :: Identity a -> Identity a # pred :: Identity a -> Identity a # toEnum :: Int -> Identity a # fromEnum :: Identity a -> Int # enumFrom :: Identity a -> [Identity a] # enumFromThen :: Identity a -> Identity a -> [Identity a] # enumFromTo :: Identity a -> Identity a -> [Identity a] # enumFromThenTo :: Identity a -> Identity a -> Identity a -> [Identity a] #
Eq a => Eq (Identity a)	Since: base-4.8.0.0
Instance details Defined in Data.Functor.Identity Methods (==) :: Identity a -> Identity a -> Bool # (/=) :: Identity a -> Identity a -> Bool #
Floating a => Floating (Identity a)	Since: base-4.9.0.0
Instance details Defined in Data.Functor.Identity Methods pi :: Identity a # exp :: Identity a -> Identity a # log :: Identity a -> Identity a # sqrt :: Identity a -> Identity a # (**) :: Identity a -> Identity a -> Identity a # logBase :: Identity a -> Identity a -> Identity a # sin :: Identity a -> Identity a # cos :: Identity a -> Identity a # tan :: Identity a -> Identity a # asin :: Identity a -> Identity a # acos :: Identity a -> Identity a # atan :: Identity a -> Identity a # sinh :: Identity a -> Identity a # cosh :: Identity a -> Identity a # tanh :: Identity a -> Identity a # asinh :: Identity a -> Identity a # acosh :: Identity a -> Identity a # atanh :: Identity a -> Identity a # log1p :: Identity a -> Identity a # expm1 :: Identity a -> Identity a # log1pexp :: Identity a -> Identity a # log1mexp :: Identity a -> Identity a #
Fractional a => Fractional (Identity a)	Since: base-4.9.0.0
Instance details Defined in Data.Functor.Identity Methods (/) :: Identity a -> Identity a -> Identity a # recip :: Identity a -> Identity a # fromRational :: Rational -> Identity a #
Integral a => Integral (Identity a)	Since: base-4.9.0.0
Instance details Defined in Data.Functor.Identity Methods quot :: Identity a -> Identity a -> Identity a # rem :: Identity a -> Identity a -> Identity a # div :: Identity a -> Identity a -> Identity a # mod :: Identity a -> Identity a -> Identity a # quotRem :: Identity a -> Identity a -> (Identity a, Identity a) # divMod :: Identity a -> Identity a -> (Identity a, Identity a) # toInteger :: Identity a -> Integer #
Num a => Num (Identity a)	Since: base-4.9.0.0
Instance details Defined in Data.Functor.Identity Methods (+) :: Identity a -> Identity a -> Identity a # (-) :: Identity a -> Identity a -> Identity a # (*) :: Identity a -> Identity a -> Identity a # negate :: Identity a -> Identity a # abs :: Identity a -> Identity a # signum :: Identity a -> Identity a # fromInteger :: Integer -> Identity a #
Ord a => Ord (Identity a)	Since: base-4.8.0.0
Instance details Defined in Data.Functor.Identity Methods compare :: Identity a -> Identity a -> Ordering # (<) :: Identity a -> Identity a -> Bool # (<=) :: Identity a -> Identity a -> Bool # (>) :: Identity a -> Identity a -> Bool # (>=) :: Identity a -> Identity a -> Bool # max :: Identity a -> Identity a -> Identity a # min :: Identity a -> Identity a -> Identity a #
Read a => Read (Identity a)	This instance would be equivalent to the derived instances of the `Identity` newtype if the `runIdentity` field were removed Since: base-4.8.0.0
Instance details Defined in Data.Functor.Identity Methods readsPrec :: Int -> ReadS (Identity a) # readList :: ReadS [Identity a] # readPrec :: ReadPrec (Identity a) # readListPrec :: ReadPrec [Identity a] #
Real a => Real (Identity a)	Since: base-4.9.0.0
Instance details Defined in Data.Functor.Identity Methods toRational :: Identity a -> Rational #
RealFloat a => RealFloat (Identity a)	Since: base-4.9.0.0
Instance details Defined in Data.Functor.Identity Methods floatRadix :: Identity a -> Integer # floatDigits :: Identity a -> Int # floatRange :: Identity a -> (Int, Int) # decodeFloat :: Identity a -> (Integer, Int) # encodeFloat :: Integer -> Int -> Identity a # exponent :: Identity a -> Int # significand :: Identity a -> Identity a # scaleFloat :: Int -> Identity a -> Identity a # isNaN :: Identity a -> Bool # isInfinite :: Identity a -> Bool # isDenormalized :: Identity a -> Bool # isNegativeZero :: Identity a -> Bool # isIEEE :: Identity a -> Bool # atan2 :: Identity a -> Identity a -> Identity a #
RealFrac a => RealFrac (Identity a)	Since: base-4.9.0.0
Instance details Defined in Data.Functor.Identity Methods properFraction :: Integral b => Identity a -> (b, Identity a) # truncate :: Integral b => Identity a -> b # round :: Integral b => Identity a -> b # ceiling :: Integral b => Identity a -> b # floor :: Integral b => Identity a -> b #
Show a => Show (Identity a)	This instance would be equivalent to the derived instances of the `Identity` newtype if the `runIdentity` field were removed Since: base-4.8.0.0
Instance details Defined in Data.Functor.Identity Methods showsPrec :: Int -> Identity a -> ShowS # show :: Identity a -> String # showList :: [Identity a] -> ShowS #
Ix a => Ix (Identity a)	Since: base-4.9.0.0
Instance details Defined in Data.Functor.Identity Methods range :: (Identity a, Identity a) -> [Identity a] # index :: (Identity a, Identity a) -> Identity a -> Int # unsafeIndex :: (Identity a, Identity a) -> Identity a -> Int inRange :: (Identity a, Identity a) -> Identity a -> Bool # rangeSize :: (Identity a, Identity a) -> Int # unsafeRangeSize :: (Identity a, Identity a) -> Int
Generic (Identity a)
Instance details Defined in Data.Functor.Identity Associated Types type Rep (Identity a) :: Type -> Type # Methods from :: Identity a -> Rep (Identity a) x # to :: Rep (Identity a) x -> Identity a #
Semigroup a => Semigroup (Identity a)	Since: base-4.9.0.0
Instance details Defined in Data.Functor.Identity Methods (<>) :: Identity a -> Identity a -> Identity a # sconcat :: NonEmpty (Identity a) -> Identity a # stimes :: Integral b => b -> Identity a -> Identity a #
Monoid a => Monoid (Identity a)	Since: base-4.9.0.0
Instance details Defined in Data.Functor.Identity Methods mempty :: Identity a # mappend :: Identity a -> Identity a -> Identity a # mconcat :: [Identity a] -> Identity a #
Storable a => Storable (Identity a)	Since: base-4.9.0.0
Instance details Defined in Data.Functor.Identity Methods sizeOf :: Identity a -> Int # alignment :: Identity a -> Int # peekElemOff :: Ptr (Identity a) -> Int -> IO (Identity a) # pokeElemOff :: Ptr (Identity a) -> Int -> Identity a -> IO () # peekByteOff :: Ptr b -> Int -> IO (Identity a) # pokeByteOff :: Ptr b -> Int -> Identity a -> IO () # peek :: Ptr (Identity a) -> IO (Identity a) # poke :: Ptr (Identity a) -> Identity a -> IO () #
Bits a => Bits (Identity a)	Since: base-4.9.0.0
Instance details Defined in Data.Functor.Identity Methods (.&.) :: Identity a -> Identity a -> Identity a # (.\|.) :: Identity a -> Identity a -> Identity a # xor :: Identity a -> Identity a -> Identity a # complement :: Identity a -> Identity a # shift :: Identity a -> Int -> Identity a # rotate :: Identity a -> Int -> Identity a # zeroBits :: Identity a # bit :: Int -> Identity a # setBit :: Identity a -> Int -> Identity a # clearBit :: Identity a -> Int -> Identity a # complementBit :: Identity a -> Int -> Identity a # testBit :: Identity a -> Int -> Bool # bitSizeMaybe :: Identity a -> Maybe Int # bitSize :: Identity a -> Int # isSigned :: Identity a -> Bool # shiftL :: Identity a -> Int -> Identity a # unsafeShiftL :: Identity a -> Int -> Identity a # shiftR :: Identity a -> Int -> Identity a # unsafeShiftR :: Identity a -> Int -> Identity a # rotateL :: Identity a -> Int -> Identity a # rotateR :: Identity a -> Int -> Identity a # popCount :: Identity a -> Int #
FiniteBits a => FiniteBits (Identity a)	Since: base-4.9.0.0
Instance details Defined in Data.Functor.Identity Methods finiteBitSize :: Identity a -> Int # countLeadingZeros :: Identity a -> Int # countTrailingZeros :: Identity a -> Int #
Generic1 Identity
Instance details Defined in Data.Functor.Identity Associated Types type Rep1 Identity :: k -> Type # Methods from1 :: Identity a -> Rep1 Identity a # to1 :: Rep1 Identity a -> Identity a #
type Rep (Identity a)	Since: base-4.8.0.0
Instance details Defined in Data.Functor.Identity type Rep (Identity a) = D1 (MetaData "Identity" "Data.Functor.Identity" "base" True) (C1 (MetaCons "Identity" PrefixI True) (S1 (MetaSel (Just "runIdentity") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 a)))
type Rep1 Identity	Since: base-4.8.0.0
Instance details Defined in Data.Functor.Identity type Rep1 Identity = D1 (MetaData "Identity" "Data.Functor.Identity" "base" True) (C1 (MetaCons "Identity" PrefixI True) (S1 (MetaSel (Just "runIdentity") NoSourceUnpackedness NoSourceStrictness DecidedLazy) Par1))

data StateT s (m :: Type -> Type) a #

A state transformer monad parameterized by:

s - The state.
m - The inner monad.

The return function leaves the state unchanged, while >>= uses the final state of the first computation as the initial state of the second.

Instances

MonadTrans (StateT s)
Instance details Defined in Control.Monad.Trans.State.Lazy Methods lift :: Monad m => m a -> StateT s m a #
Monad m => Monad (StateT s m)
Instance details Defined in Control.Monad.Trans.State.Lazy Methods (>>=) :: StateT s m a -> (a -> StateT s m b) -> StateT s m b # (>>) :: StateT s m a -> StateT s m b -> StateT s m b # return :: a -> StateT s m a # fail :: String -> StateT s m a #
Functor m => Functor (StateT s m)
Instance details Defined in Control.Monad.Trans.State.Lazy Methods fmap :: (a -> b) -> StateT s m a -> StateT s m b # (<$) :: a -> StateT s m b -> StateT s m a #
MonadFix m => MonadFix (StateT s m)
Instance details Defined in Control.Monad.Trans.State.Lazy Methods mfix :: (a -> StateT s m a) -> StateT s m a #
MonadFail m => MonadFail (StateT s m)
Instance details Defined in Control.Monad.Trans.State.Lazy Methods fail :: String -> StateT s m a #
(Functor m, Monad m) => Applicative (StateT s m)
Instance details Defined in Control.Monad.Trans.State.Lazy Methods pure :: a -> StateT s m a # (<>) :: StateT s m (a -> b) -> StateT s m a -> StateT s m b # liftA2 :: (a -> b -> c) -> StateT s m a -> StateT s m b -> StateT s m c # (>) :: StateT s m a -> StateT s m b -> StateT s m b # (<*) :: StateT s m a -> StateT s m b -> StateT s m a #
Contravariant m => Contravariant (StateT s m)
Instance details Defined in Control.Monad.Trans.State.Lazy Methods contramap :: (a -> b) -> StateT s m b -> StateT s m a # (>$) :: b -> StateT s m b -> StateT s m a #
MonadIO m => MonadIO (StateT s m)
Instance details Defined in Control.Monad.Trans.State.Lazy Methods liftIO :: IO a -> StateT s m a #
(Functor m, MonadPlus m) => Alternative (StateT s m)
Instance details Defined in Control.Monad.Trans.State.Lazy Methods empty :: StateT s m a # (<\|>) :: StateT s m a -> StateT s m a -> StateT s m a # some :: StateT s m a -> StateT s m [a] # many :: StateT s m a -> StateT s m [a] #
MonadPlus m => MonadPlus (StateT s m)
Instance details Defined in Control.Monad.Trans.State.Lazy Methods mzero :: StateT s m a # mplus :: StateT s m a -> StateT s m a -> StateT s m a #

type Writer w = WriterT w Identity #

A writer monad parameterized by the type w of output to accumulate.

The return function produces the output mempty, while >>= combines the outputs of the subcomputations using mappend.