lens-family-2.1.0: Lens Families

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LanguageHaskell98

Lens.Family2.State.Lazy

Contents

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

Documentation

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

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 :: MonadState s m => FoldLike a s t a b -> m a Source #

use :: MonadState s m => Getter s t a b -> m a

Retrieve a field of the state

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

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

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

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

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

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

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

uses l f = f <$> use l

(%=) :: MonadState s m => Setter s s a b -> (a -> b) -> m () infix 4 Source #

Modify a field of the state.

assign :: MonadState s m => Setter s s a b -> b -> m () Source #

Set a field of the state.

(.=) :: MonadState s m => Setter s s a b -> b -> m () infix 4 Source #

Set a field of the state.

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

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

Modify a field of the state while returning another value.

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

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

(<~) :: MonadState s m => Setter s s a b -> m b -> m () infixr 2 Source #

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

Compound Assignments

(+=) :: (MonadState s m, Num a) => Setter' s a -> a -> m () infixr 4 Source #

(-=) :: (MonadState s m, Num a) => Setter' s a -> a -> m () infixr 4 Source #

(*=) :: (MonadState s m, Num a) => Setter' s a -> a -> m () infixr 4 Source #

(//=) :: (MonadState s m, Fractional a) => Setter' s a -> a -> m () infixr 4 Source #

(&&=) :: MonadState s m => Setter' s Bool -> Bool -> m () infixr 4 Source #

(||=) :: MonadState s m => Setter' s Bool -> Bool -> m () infixr 4 Source #

(<>=) :: (MonadState s m, Monoid a) => Setter' s a -> a -> m () infixr 4 Source #

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

Strict Assignments

(%!=) :: MonadState s m => Setter s s a b -> (a -> b) -> m () infix 4 Source #

Strictly modify a field of the state.

(+!=) :: (MonadState s m, Num a) => Setter' s a -> a -> m () infixr 4 Source #

(-!=) :: (MonadState s m, Num a) => Setter' s a -> a -> m () infixr 4 Source #

(*!=) :: (MonadState s m, Num a) => Setter' s a -> a -> m () infixr 4 Source #

(//!=) :: (MonadState s m, Fractional a) => Setter' s a -> a -> m () infixr 4 Source #

(&&!=) :: MonadState s m => Setter' s Bool -> Bool -> m () infixr 4 Source #

(||!=) :: MonadState s m => Setter' s Bool -> Bool -> m () infixr 4 Source #

(<>!=) :: (MonadState s m, Monoid a) => Setter' s a -> a -> m () infixr 4 Source #

Types

data Zooming (m :: Type -> Type) c a #

Instances
Monad m => Functor (Zooming m c) 
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) 
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 :: Type -> Type) s t a b = (a -> f b) -> s -> f t #

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

type FoldLike r s t a b = LensLike (Constant r :: Type -> Type) s t a b #

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) 
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

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 Setter s t a b = forall f. Identical f => LensLike f s t a b Source #

type Setter' s a = forall f. Identical f => LensLike' f s a Source #

class (Traversable f, Applicative f) => Identical (f :: Type -> Type) #

Minimal complete definition

extract

Instances
Identical Identity 
Instance details

Defined in Lens.Family.Identical

Methods

extract :: Identity a -> a

Identical f => Identical (Backwards f) 
Instance details

Defined in Lens.Family.Identical

Methods

extract :: Backwards f a -> a

(Identical f, Identical g) => Identical (Compose f g) 
Instance details

Defined in Lens.Family.Identical

Methods

extract :: Compose f g a -> a

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
Monad m => MonadState s (StateT s m) 
Instance details

Defined in Control.Monad.State.Class

Methods

get :: StateT s m s #

put :: s -> StateT s m () #

state :: (s -> (a, s)) -> StateT s m a #

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 #

class Monad m => MonadState s (m :: Type -> Type) | m -> s #

Minimal definition is either both of get and put or just state

Minimal complete definition

state | get, put

Instances
MonadState s m => MonadState s (MaybeT m) 
Instance details

Defined in Control.Monad.State.Class

Methods

get :: MaybeT m s #

put :: s -> MaybeT m () #

state :: (s -> (a, s)) -> MaybeT m a #

MonadState s m => MonadState s (ListT m) 
Instance details

Defined in Control.Monad.State.Class

Methods

get :: ListT m s #

put :: s -> ListT m () #

state :: (s -> (a, s)) -> ListT m a #

(Monoid w, MonadState s m) => MonadState s (WriterT w m) 
Instance details

Defined in Control.Monad.State.Class

Methods

get :: WriterT w m s #

put :: s -> WriterT w m () #

state :: (s -> (a, s)) -> WriterT w m a #

(Monoid w, MonadState s m) => MonadState s (WriterT w m) 
Instance details

Defined in Control.Monad.State.Class

Methods

get :: WriterT w m s #

put :: s -> WriterT w m () #

state :: (s -> (a, s)) -> WriterT w m a #

Monad m => MonadState s (StateT s m) 
Instance details

Defined in Control.Monad.State.Class

Methods

get :: StateT s m s #

put :: s -> StateT s m () #

state :: (s -> (a, s)) -> StateT s m a #

Monad m => MonadState s (StateT s m) 
Instance details

Defined in Control.Monad.State.Class

Methods

get :: StateT s m s #

put :: s -> StateT s m () #

state :: (s -> (a, s)) -> StateT s m a #

MonadState s m => MonadState s (IdentityT m) 
Instance details

Defined in Control.Monad.State.Class

Methods

get :: IdentityT m s #

put :: s -> IdentityT m () #

state :: (s -> (a, s)) -> IdentityT m a #

MonadState s m => MonadState s (ExceptT e m)

Since: mtl-2.2

Instance details

Defined in Control.Monad.State.Class

Methods

get :: ExceptT e m s #

put :: s -> ExceptT e m () #

state :: (s -> (a, s)) -> ExceptT e m a #

(Error e, MonadState s m) => MonadState s (ErrorT e m) 
Instance details

Defined in Control.Monad.State.Class

Methods

get :: ErrorT e m s #

put :: s -> ErrorT e m () #

state :: (s -> (a, s)) -> ErrorT e m a #

MonadState s m => MonadState s (ReaderT r m) 
Instance details

Defined in Control.Monad.State.Class

Methods

get :: ReaderT r m s #

put :: s -> ReaderT r m () #

state :: (s -> (a, s)) -> ReaderT r m a #

MonadState s m => MonadState s (ContT r m) 
Instance details

Defined in Control.Monad.State.Class

Methods

get :: ContT r m s #

put :: s -> ContT r m () #

state :: (s -> (a, s)) -> ContT r m a #

(Monad m, Monoid w) => MonadState s (RWST r w s m) 
Instance details

Defined in Control.Monad.State.Class

Methods

get :: RWST r w s m s #

put :: s -> RWST r w s m () #

state :: (s -> (a, s)) -> RWST r w s m a #

(Monad m, Monoid w) => MonadState s (RWST r w s m) 
Instance details

Defined in Control.Monad.State.Class

Methods

get :: RWST r w s m s #

put :: s -> RWST r w s m () #

state :: (s -> (a, s)) -> RWST r w 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.