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Language	Haskell98

Lens.Family2.State.Lazy

Contents

Compound 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

Documentation

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

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

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

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

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

use :: MonadState a m => FoldLike b a a' b b' -> m b #

use :: MonadState a m => Getter a a' b b' -> m b

Retrieve a field of the state

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

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

uses :: MonadState a m => FoldLike r a a' b b' -> (b -> r) -> m r #

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

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

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

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

uses l f = f <$> use l

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

Modify a field of the state.

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

Set a field of the state.

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

Set a field of the state.

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

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

Modify a field of the state while returning another value.

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

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

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

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

Compound Assignments

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

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

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

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

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

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

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

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

Types

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

Instances

Monad m => Functor (Zooming m c)
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)
Methods pure :: a -> Zooming m c a # (<>) :: Zooming m c (a -> b) -> Zooming m c a -> Zooming m c b # (>) :: 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 a a' b b' = (b -> f b') -> a -> f a' #

type LensLike' f a b = (b -> f b) -> a -> f a #

type FoldLike r a a' b b' = LensLike (Constant * r) a a' b b' #

data Constant k a b :: forall k. * -> k -> * #

Constant functor.

Instances

Eq2 (Constant *)
Methods liftEq2 :: (a -> b -> Bool) -> (c -> d -> Bool) -> Constant * a c -> Constant * b d -> Bool #
Ord2 (Constant *)
Methods liftCompare2 :: (a -> b -> Ordering) -> (c -> d -> Ordering) -> Constant * a c -> Constant * b d -> Ordering #
Read2 (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] #
Show2 (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 #
Bifunctor (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 #
Functor (Constant * a)
Methods fmap :: (a -> b) -> Constant * a a -> Constant * a b # (<$) :: a -> Constant * a b -> Constant * a a #
Monoid a => Applicative (Constant * a)
Methods pure :: a -> Constant * a a # (<>) :: Constant a (a -> b) -> Constant * a a -> Constant * a b # (>) :: Constant a a -> Constant * a b -> Constant * a b # (<) :: Constant a a -> Constant * a b -> Constant * a a #
Foldable (Constant * a)
Methods fold :: Monoid m => Constant * a m -> m # foldMap :: Monoid m => (a -> m) -> Constant * a a -> m # foldr :: (a -> b -> b) -> b -> Constant * a a -> b # foldr' :: (a -> b -> b) -> b -> Constant * a a -> b # foldl :: (b -> a -> b) -> b -> Constant * a a -> b # foldl' :: (b -> a -> b) -> b -> Constant * a a -> b # foldr1 :: (a -> a -> a) -> Constant * a a -> a # foldl1 :: (a -> a -> a) -> Constant * a a -> a # toList :: Constant * a a -> [a] # null :: Constant * a a -> Bool # length :: Constant * a a -> Int # elem :: Eq a => a -> Constant * a a -> Bool # maximum :: Ord a => Constant * a a -> a # minimum :: Ord a => Constant * a a -> a # sum :: Num a => Constant * a a -> a # product :: Num a => Constant * a a -> a #
Traversable (Constant * a)
Methods traverse :: Applicative f => (a -> f b) -> Constant * a a -> f (Constant * a b) # sequenceA :: Applicative f => Constant * a (f a) -> f (Constant * a a) # mapM :: Monad m => (a -> m b) -> Constant * a a -> m (Constant * a b) # sequence :: Monad m => Constant * a (m a) -> m (Constant * a a) #
Eq a => Eq1 (Constant * a)
Methods liftEq :: (a -> b -> Bool) -> Constant * a a -> Constant * a b -> Bool #
Ord a => Ord1 (Constant * a)
Methods liftCompare :: (a -> b -> Ordering) -> Constant * a a -> Constant * a b -> Ordering #
Read a => Read1 (Constant * a)
Methods liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (Constant * a a) # liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [Constant * a a] #
Show a => Show1 (Constant * a)
Methods liftShowsPrec :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> Int -> Constant * a a -> ShowS # liftShowList :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> [Constant * a a] -> ShowS #
Phantom (Constant * a)
Methods coerce :: Constant * a a -> Constant * a b
Eq a => Eq (Constant k a b)
Methods (==) :: Constant k a b -> Constant k a b -> Bool # (/=) :: Constant k a b -> Constant k a b -> Bool #
Ord a => Ord (Constant k a b)
Methods compare :: Constant k a b -> Constant k a b -> Ordering # (<) :: Constant k a b -> Constant k a b -> Bool # (<=) :: Constant k a b -> Constant k a b -> Bool # (>) :: Constant k a b -> Constant k a b -> Bool # (>=) :: Constant k a b -> Constant k a b -> Bool # max :: Constant k a b -> Constant k a b -> Constant k a b # min :: Constant k a b -> Constant k a b -> Constant k a b #
Read a => Read (Constant k a b)
Methods readsPrec :: Int -> ReadS (Constant k a b) # readList :: ReadS [Constant k a b] # readPrec :: ReadPrec (Constant k a b) # readListPrec :: ReadPrec [Constant k a b] #
Show a => Show (Constant k a b)
Methods showsPrec :: Int -> Constant k a b -> ShowS # show :: Constant k a b -> String # showList :: [Constant k a b] -> ShowS #
Monoid a => Monoid (Constant k a b)
Methods mempty :: Constant k a b # mappend :: Constant k a b -> Constant k a b -> Constant k a b # mconcat :: [Constant k a b] -> Constant k a b #

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

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

class Applicative f => Identical f #

Minimal complete definition

extract

Instances

Identical Identity
Methods extract :: Identity a -> a
Identical f => Identical (Backwards * f)
Methods extract :: Backwards * f a -> a
(Identical f, Identical g) => Identical (Compose * * f g)
Methods extract :: Compose * * f g a -> a

data StateT s m 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)
Methods get :: StateT s m s # put :: s -> StateT s m () # state :: (s -> (a, s)) -> StateT s m a #
MonadTrans (StateT s)
Methods lift :: Monad m => m a -> StateT s m a #
Monad m => Monad (StateT s m)
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)
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)
Methods mfix :: (a -> StateT s m a) -> StateT s m a #
MonadFail m => MonadFail (StateT s m)
Methods fail :: String -> StateT s m a #
(Functor m, Monad m) => Applicative (StateT s m)
Methods pure :: a -> StateT s m a # (<>) :: StateT s m (a -> b) -> StateT s m a -> StateT s m b # (>) :: StateT s m a -> StateT s m b -> StateT s m b # (<*) :: StateT s m a -> StateT s m b -> StateT s m a #
MonadIO m => MonadIO (StateT s m)
Methods liftIO :: IO a -> StateT s m a #
(Functor m, MonadPlus m) => Alternative (StateT s m)
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)
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 | 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)
Methods get :: MaybeT m s # put :: s -> MaybeT m () # state :: (s -> (a, s)) -> MaybeT m a #
MonadState s m => MonadState s (ListT m)
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)
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)
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)
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)
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)
Methods get :: IdentityT * m s # put :: s -> IdentityT * m () # state :: (s -> (a, s)) -> IdentityT * m a #
MonadState s m => MonadState s (ExceptT e m)
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)
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)
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)
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)
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)
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.

class Monoid a #

The class of monoids (types with an associative binary operation that has an identity). Instances should satisfy the following laws:

```
mappend mempty x = x
```
```
mappend x mempty = x
```

mappend x (mappend y z) = mappend (mappend x y) z

```
mconcat = foldr mappend mempty
```

The method names refer to the monoid of lists under concatenation, but there are many other instances.

Some types can be viewed as a monoid in more than one way, e.g. both addition and multiplication on numbers. In such cases we often define newtypes and make those instances of Monoid, e.g. Sum and Product.

Minimal complete definition

mempty, mappend

Instances

Monoid Ordering
Methods mempty :: Ordering # mappend :: Ordering -> Ordering -> Ordering # mconcat :: [Ordering] -> Ordering #
Monoid ()
Methods mempty :: () # mappend :: () -> () -> () # mconcat :: [()] -> () #
Monoid All
Methods mempty :: All # mappend :: All -> All -> All # mconcat :: [All] -> All #
Monoid Any
Methods mempty :: Any # mappend :: Any -> Any -> Any # mconcat :: [Any] -> Any #
Monoid IntSet
Methods mempty :: IntSet # mappend :: IntSet -> IntSet -> IntSet # mconcat :: [IntSet] -> IntSet #
Monoid [a]
Methods mempty :: [a] # mappend :: [a] -> [a] -> [a] # mconcat :: [[a]] -> [a] #
Monoid a => Monoid (Maybe a)	Lift a semigroup into `Maybe` forming a `Monoid` according to http://en.wikipedia.org/wiki/Monoid: "Any semigroup `S` may be turned into a monoid simply by adjoining an element `e` not in `S` and defining `ee = e` and `es = s = s*e` for all `s ∈ S`." Since there is no "Semigroup" typeclass providing just `mappend`, we use `Monoid` instead.
Methods mempty :: Maybe a # mappend :: Maybe a -> Maybe a -> Maybe a # mconcat :: [Maybe a] -> Maybe a #
Monoid a => Monoid (IO a)
Methods mempty :: IO a # mappend :: IO a -> IO a -> IO a # mconcat :: [IO a] -> IO a #
Ord a => Monoid (Max a)
Methods mempty :: Max a # mappend :: Max a -> Max a -> Max a # mconcat :: [Max a] -> Max a #
Ord a => Monoid (Min a)
Methods mempty :: Min a # mappend :: Min a -> Min a -> Min a # mconcat :: [Min a] -> Min a #
Monoid a => Monoid (Identity a)
Methods mempty :: Identity a # mappend :: Identity a -> Identity a -> Identity a # mconcat :: [Identity a] -> Identity a #
Monoid a => Monoid (Dual a)
Methods mempty :: Dual a # mappend :: Dual a -> Dual a -> Dual a # mconcat :: [Dual a] -> Dual a #
Monoid (Endo a)
Methods mempty :: Endo a # mappend :: Endo a -> Endo a -> Endo a # mconcat :: [Endo a] -> Endo a #
Num a => Monoid (Sum a)
Methods mempty :: Sum a # mappend :: Sum a -> Sum a -> Sum a # mconcat :: [Sum a] -> Sum a #
Num a => Monoid (Product a)
Methods mempty :: Product a # mappend :: Product a -> Product a -> Product a # mconcat :: [Product a] -> Product a #
Monoid (First a)
Methods mempty :: First a # mappend :: First a -> First a -> First a # mconcat :: [First a] -> First a #
Monoid (Last a)
Methods mempty :: Last a # mappend :: Last a -> Last a -> Last a # mconcat :: [Last a] -> Last a #
Monoid (IntMap a)
Methods mempty :: IntMap a # mappend :: IntMap a -> IntMap a -> IntMap a # mconcat :: [IntMap a] -> IntMap a #
Ord a => Monoid (Set a)
Methods mempty :: Set a # mappend :: Set a -> Set a -> Set a # mconcat :: [Set a] -> Set a #
Monoid b => Monoid (a -> b)
Methods mempty :: a -> b # mappend :: (a -> b) -> (a -> b) -> a -> b # mconcat :: [a -> b] -> a -> b #
(Monoid a, Monoid b) => Monoid (a, b)
Methods mempty :: (a, b) # mappend :: (a, b) -> (a, b) -> (a, b) # mconcat :: [(a, b)] -> (a, b) #
Monoid (Proxy k s)
Methods mempty :: Proxy k s # mappend :: Proxy k s -> Proxy k s -> Proxy k s # mconcat :: [Proxy k s] -> Proxy k s #
Ord k => Monoid (Map k v)
Methods mempty :: Map k v # mappend :: Map k v -> Map k v -> Map k v # mconcat :: [Map k v] -> Map k v #
(Monoid a, Monoid b, Monoid c) => Monoid (a, b, c)
Methods mempty :: (a, b, c) # mappend :: (a, b, c) -> (a, b, c) -> (a, b, c) # mconcat :: [(a, b, c)] -> (a, b, c) #
Alternative f => Monoid (Alt * f a)
Methods mempty :: Alt * f a # mappend :: Alt * f a -> Alt * f a -> Alt * f a # mconcat :: [Alt * f a] -> Alt * f a #
Monoid a => Monoid (Constant k a b)
Methods mempty :: Constant k a b # mappend :: Constant k a b -> Constant k a b -> Constant k a b # mconcat :: [Constant k a b] -> Constant k a b #
(Monoid a, Monoid b, Monoid c, Monoid d) => Monoid (a, b, c, d)
Methods mempty :: (a, b, c, d) # mappend :: (a, b, c, d) -> (a, b, c, d) -> (a, b, c, d) # mconcat :: [(a, b, c, d)] -> (a, b, c, d) #
(Monoid a, Monoid b, Monoid c, Monoid d, Monoid e) => Monoid (a, b, c, d, e)
Methods mempty :: (a, b, c, d, e) # mappend :: (a, b, c, d, e) -> (a, b, c, d, e) -> (a, b, c, d, e) # mconcat :: [(a, b, c, d, e)] -> (a, b, c, d, e) #