Control.Lens.Zoom

Documentation

type family Magnified (m :: * -> *) :: * -> * -> *

This type family is used by Magnify to describe the common effect type.

Instances

type Magnified (IdentityT m)

Defined in Control.Lens.Zoom

type Magnified (IdentityT m) = Magnified m

type Magnified (ReaderT b m)

Defined in Control.Lens.Zoom

type Magnified (ReaderT b m) = Effect m

type Magnified ((->) b :: Type -> Type)

Defined in Control.Lens.Zoom

type Magnified ((->) b :: Type -> Type) = Const :: Type -> Type -> Type

type Magnified (RWST a w s m)

Defined in Control.Lens.Zoom

type Magnified (RWST a w s m) = EffectRWS w s m

type Magnified (RWST a w s m)

Defined in Control.Lens.Zoom

type Magnified (RWST a w s m) = EffectRWS w s m

class (Magnified m ~ Magnified n, MonadReader b m, MonadReader a n) => Magnify m n b a | m -> b, n -> a, m a -> n, n b -> m where

This class allows us to use magnify part of the environment, changing the environment supplied by many different Monad transformers. Unlike zoom this can change the environment of a deeply nested Monad transformer.

Also, unlike zoom, this can be used with any valid Getter, but cannot be used with a Traversal or Fold.

Methods

magnify :: ((Functor (Magnified m c), Contravariant (Magnified m c)) => LensLike' (Magnified m c) a b) -> m c -> n c infixr 2

Run a monadic action in a larger environment than it was defined in, using a Getter.

This acts like local, but can in many cases change the type of the environment as well.

This is commonly used to lift actions in a simpler Reader Monad into a Monad with a larger environment type.

This can be used to edit pretty much any Monad transformer stack with an environment in it:

>>> (1,2) & magnify _2 (+1)
3

>>> flip Reader.runReader (1,2) $ magnify _1 Reader.ask
1

>>> flip Reader.runReader (1,2,[10..20]) $ magnify (_3._tail) Reader.ask
[11,12,13,14,15,16,17,18,19,20]

The type can be read as

  magnify :: LensLike' (Magnified m c) a b -> m c -> n c

but the higher-rank constraints make it easier to apply magnify to a Getter in highly-polymorphic code.

magnify :: Getter s a -> (a -> r) -> s -> r
magnify :: Monoid r => Fold s a   -> (a -> r) -> s -> r

magnify :: Monoid w                 => Getter s t -> RWS t w st c -> RWS s w st c
magnify :: (Monoid w, Monoid c) => Fold s a   -> RWS a w st c -> RWS s w st c
...

Instances

Magnify m n b a => Magnify (IdentityT m) (IdentityT n) b a

Defined in Control.Lens.Zoom

Methods

magnify :: ((Functor (Magnified (IdentityT m) c), Contravariant (Magnified (IdentityT m) c)) => LensLike' (Magnified (IdentityT m) c) a b) -> IdentityT m c -> IdentityT n c

Monad m => Magnify (ReaderT b m) (ReaderT a m) b a

Defined in Control.Lens.Zoom

Methods

magnify :: ((Functor (Magnified (ReaderT b m) c), Contravariant (Magnified (ReaderT b m) c)) => LensLike' (Magnified (ReaderT b m) c) a b) -> ReaderT b m c -> ReaderT a m c

Magnify ((->) b :: Type -> Type) ((->) a :: Type -> Type) b a

magnify = views

Defined in Control.Lens.Zoom

Methods

magnify :: ((Functor (Magnified ((->) b) c), Contravariant (Magnified ((->) b) c)) => LensLike' (Magnified ((->) b) c) a b) -> (b -> c) -> a -> c

(Monad m, Monoid w) => Magnify (RWST b w s m) (RWST a w s m) b a

Defined in Control.Lens.Zoom

Methods

magnify :: ((Functor (Magnified (RWST b w s m) c), Contravariant (Magnified (RWST b w s m) c)) => LensLike' (Magnified (RWST b w s m) c) a b) -> RWST b w s m c -> RWST a w s m c

(Monad m, Monoid w) => Magnify (RWST b w s m) (RWST a w s m) b a

Defined in Control.Lens.Zoom

Methods

magnify :: ((Functor (Magnified (RWST b w s m) c), Contravariant (Magnified (RWST b w s m) c)) => LensLike' (Magnified (RWST b w s m) c) a b) -> RWST b w s m c -> RWST a w s m c

class (MonadState s m, MonadState t n) => Zoom m n s t | m -> s, n -> t, m t -> n, n s -> m where

This class allows us to use zoom in, changing the State supplied by many different Monad transformers, potentially quite deep in a Monad transformer stack.

Methods

zoom :: LensLike' (Zoomed m c) t s -> m c -> n c infixr 2

Run a monadic action in a larger State than it was defined in, using a Lens' or Traversal'.

This is commonly used to lift actions in a simpler State Monad into a State Monad with a larger State type.

When applied to a Traversal' over multiple values, the actions for each target are executed sequentially and the results are aggregated.

This can be used to edit pretty much any Monad transformer stack with a State in it!

>>> flip State.evalState (a,b) $ zoom _1 $ use id
a

>>> flip State.execState (a,b) $ zoom _1 $ id .= c
(c,b)

>>> flip State.execState [(a,b),(c,d)] $ zoom traverse $ _2 %= f
[(a,f b),(c,f d)]

>>> flip State.runState [(a,b),(c,d)] $ zoom traverse $ _2 <%= f
(f b <> f d <> mempty,[(a,f b),(c,f d)])

>>> flip State.evalState (a,b) $ zoom both (use id)
a <> b

zoom :: Monad m             => Lens' s t      -> StateT t m a -> StateT s m a
zoom :: (Monad m, Monoid c) => Traversal' s t -> StateT t m c -> StateT s m c
zoom :: (Monad m, Monoid w)             => Lens' s t      -> RWST r w t m c -> RWST r w s m c
zoom :: (Monad m, Monoid w, Monoid c) => Traversal' s t -> RWST r w t m c -> RWST r w s m c
zoom :: (Monad m, Monoid w, Error e)  => Lens' s t      -> ErrorT e (RWST r w t m) c -> ErrorT e (RWST r w s m) c
zoom :: (Monad m, Monoid w, Monoid c, Error e) => Traversal' s t -> ErrorT e (RWST r w t m) c -> ErrorT e (RWST r w s m) c
...

Instances

Zoom m n s t => Zoom (MaybeT m) (MaybeT n) s t

Defined in Control.Lens.Zoom

Methods

zoom :: LensLike' (Zoomed (MaybeT m) c) t s -> MaybeT m c -> MaybeT n c

Zoom m n s t => Zoom (ListT m) (ListT n) s t

Defined in Control.Lens.Zoom

Methods

zoom :: LensLike' (Zoomed (ListT m) c) t s -> ListT m c -> ListT n c

Zoom m n s t => Zoom (IdentityT m) (IdentityT n) s t

Defined in Control.Lens.Zoom

Methods

zoom :: LensLike' (Zoomed (IdentityT m) c) t s -> IdentityT m c -> IdentityT n c

Zoom m n s t => Zoom (ExceptT e m) (ExceptT e n) s t

Defined in Control.Lens.Zoom

Methods

zoom :: LensLike' (Zoomed (ExceptT e m) c) t s -> ExceptT e m c -> ExceptT e n c

(Functor f, Zoom m n s t) => Zoom (FreeT f m) (FreeT f n) s t

Defined in Control.Lens.Zoom

Methods

zoom :: LensLike' (Zoomed (FreeT f m) c) t s -> FreeT f m c -> FreeT f n c

(Error e, Zoom m n s t) => Zoom (ErrorT e m) (ErrorT e n) s t

Defined in Control.Lens.Zoom

Methods

zoom :: LensLike' (Zoomed (ErrorT e m) c) t s -> ErrorT e m c -> ErrorT e n c

Zoom m n s t => Zoom (ReaderT e m) (ReaderT e n) s t

Defined in Control.Lens.Zoom

Methods

zoom :: LensLike' (Zoomed (ReaderT e m) c) t s -> ReaderT e m c -> ReaderT e n c

Monad z => Zoom (StateT s z) (StateT t z) s t

Defined in Control.Lens.Zoom

Methods

zoom :: LensLike' (Zoomed (StateT s z) c) t s -> StateT s z c -> StateT t z c

Monad z => Zoom (StateT s z) (StateT t z) s t

Defined in Control.Lens.Zoom

Methods

zoom :: LensLike' (Zoomed (StateT s z) c) t s -> StateT s z c -> StateT t z c

(Monoid w, Zoom m n s t) => Zoom (WriterT w m) (WriterT w n) s t

Defined in Control.Lens.Zoom

Methods

zoom :: LensLike' (Zoomed (WriterT w m) c) t s -> WriterT w m c -> WriterT w n c

(Monoid w, Zoom m n s t) => Zoom (WriterT w m) (WriterT w n) s t

Defined in Control.Lens.Zoom

Methods

zoom :: LensLike' (Zoomed (WriterT w m) c) t s -> WriterT w m c -> WriterT w n c

(Monoid w, Monad z) => Zoom (RWST r w s z) (RWST r w t z) s t

Defined in Control.Lens.Zoom

Methods

zoom :: LensLike' (Zoomed (RWST r w s z) c) t s -> RWST r w s z c -> RWST r w t z c

(Monoid w, Monad z) => Zoom (RWST r w s z) (RWST r w t z) s t

Defined in Control.Lens.Zoom

Methods

zoom :: LensLike' (Zoomed (RWST r w s z) c) t s -> RWST r w s z c -> RWST r w t z c

type family Zoomed (m :: * -> *) :: * -> * -> *

This type family is used by Zoom to describe the common effect type.

Instances

type Zoomed (MaybeT m)

Defined in Control.Lens.Zoom

type Zoomed (MaybeT m) = FocusingMay (Zoomed m)

type Zoomed (ListT m)

Defined in Control.Lens.Zoom

type Zoomed (ListT m) = FocusingOn [] (Zoomed m)

type Zoomed (IdentityT m)

Defined in Control.Lens.Zoom

type Zoomed (IdentityT m) = Zoomed m

type Zoomed (ExceptT e m)

Defined in Control.Lens.Zoom

type Zoomed (ExceptT e m) = FocusingErr e (Zoomed m)

type Zoomed (FreeT f m)

Defined in Control.Lens.Zoom

type Zoomed (FreeT f m) = FocusingFree f m (Zoomed m)

type Zoomed (ErrorT e m)

Defined in Control.Lens.Zoom

type Zoomed (ErrorT e m) = FocusingErr e (Zoomed m)

type Zoomed (ReaderT e m)

Defined in Control.Lens.Zoom

type Zoomed (ReaderT e m) = Zoomed m

type Zoomed (StateT s z)

Defined in Control.Lens.Zoom

type Zoomed (StateT s z) = Focusing z

type Zoomed (StateT s z)

Defined in Control.Lens.Zoom

type Zoomed (StateT s z) = Focusing z

type Zoomed (WriterT w m)

Defined in Control.Lens.Zoom

type Zoomed (WriterT w m) = FocusingPlus w (Zoomed m)

type Zoomed (WriterT w m)

Defined in Control.Lens.Zoom

type Zoomed (WriterT w m) = FocusingPlus w (Zoomed m)

type Zoomed (RWST r w s z)

Defined in Control.Lens.Zoom

type Zoomed (RWST r w s z) = FocusingWith w z

type Zoomed (RWST r w s z)

Defined in Control.Lens.Zoom

type Zoomed (RWST r w s z) = FocusingWith w z