Copyright	(C) 2012-16 Edward Kmett
License	BSD-style (see the file LICENSE)
Maintainer	Edward Kmett <ekmett@gmail.com>
Stability	provisional
Portability	Rank2Types
Safe Haskell	Trustworthy
Language	Haskell2010

Control.Lens.Zoom

Description

Synopsis

type family Magnified (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
- magnify :: (( Functor ( Magnified m c), Contravariant ( Magnified m c)) => LensLike' ( Magnified m c) a b) -> m c -> n c
class ( MonadState s m, MonadState t n) => Zoom m n s t | m -> s, n -> t, m t -> n, n s -> m where
- zoom :: LensLike' ( Zoomed m c) t s -> m c -> n c
type family Zoomed (m :: * -> *) :: * -> * -> *

Documentation

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

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

Instances

Instances details

type Magnified ( IdentityT m) Source #
Instance details Defined in Control.Lens.Zoom type Magnified ( IdentityT m) = Magnified m
type Magnified ( ReaderT b m) Source #
Instance details Defined in Control.Lens.Zoom type Magnified ( ReaderT b m) = Effect m
type Magnified ((->) b :: Type -> Type ) Source #
Instance details Defined in Control.Lens.Zoom type Magnified ((->) b :: Type -> Type ) = Const :: Type -> Type -> Type
type Magnified ( RWST a w s m) Source #
Instance details Defined in Control.Lens.Zoom type Magnified ( RWST a w s m) = EffectRWS w s m
type Magnified ( RWST a w s m) Source #
Instance details 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 Source #

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 Source #

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

Instances details

Magnify m n b a => Magnify ( IdentityT m) ( IdentityT n) b a Source #
Instance details 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 Source #
Monad m => Magnify ( ReaderT b m) ( ReaderT a m) b a Source #
Instance details 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 Source #
Magnify ((->) b :: Type -> Type ) ((->) a :: Type -> Type ) b a Source #	`magnify` = `views`
Instance details 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 Source #
( Monad m, Monoid w) => Magnify ( RWST b w s m) ( RWST a w s m) b a Source #
Instance details 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 Source #
( Monad m, Monoid w) => Magnify ( RWST b w s m) ( RWST a w s m) b a Source #
Instance details 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 Source #

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

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 Source #

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

Instances details

Zoom m n s t => Zoom ( MaybeT m) ( MaybeT n) s t Source #
Instance details Defined in Control.Lens.Zoom Methods zoom :: LensLike' ( Zoomed ( MaybeT m) c) t s -> MaybeT m c -> MaybeT n c Source #
Zoom m n s t => Zoom ( ListT m) ( ListT n) s t Source #
Instance details Defined in Control.Lens.Zoom Methods zoom :: LensLike' ( Zoomed ( ListT m) c) t s -> ListT m c -> ListT n c Source #
Zoom m n s t => Zoom ( IdentityT m) ( IdentityT n) s t Source #
Instance details Defined in Control.Lens.Zoom Methods zoom :: LensLike' ( Zoomed ( IdentityT m) c) t s -> IdentityT m c -> IdentityT n c Source #
Zoom m n s t => Zoom ( ExceptT e m) ( ExceptT e n) s t Source #
Instance details Defined in Control.Lens.Zoom Methods zoom :: LensLike' ( Zoomed ( ExceptT e m) c) t s -> ExceptT e m c -> ExceptT e n c Source #
( Functor f, Zoom m n s t) => Zoom ( FreeT f m) ( FreeT f n) s t Source #
Instance details Defined in Control.Lens.Zoom Methods zoom :: LensLike' ( Zoomed ( FreeT f m) c) t s -> FreeT f m c -> FreeT f n c Source #
( Error e, Zoom m n s t) => Zoom ( ErrorT e m) ( ErrorT e n) s t Source #
Instance details Defined in Control.Lens.Zoom Methods zoom :: LensLike' ( Zoomed ( ErrorT e m) c) t s -> ErrorT e m c -> ErrorT e n c Source #
Zoom m n s t => Zoom ( ReaderT e m) ( ReaderT e n) s t Source #
Instance details Defined in Control.Lens.Zoom Methods zoom :: LensLike' ( Zoomed ( ReaderT e m) c) t s -> ReaderT e m c -> ReaderT e n c Source #
Monad z => Zoom ( StateT s z) ( StateT t z) s t Source #
Instance details Defined in Control.Lens.Zoom Methods zoom :: LensLike' ( Zoomed ( StateT s z) c) t s -> StateT s z c -> StateT t z c Source #
Monad z => Zoom ( StateT s z) ( StateT t z) s t Source #
Instance details Defined in Control.Lens.Zoom Methods zoom :: LensLike' ( Zoomed ( StateT s z) c) t s -> StateT s z c -> StateT t z c Source #
( Monoid w, Zoom m n s t) => Zoom ( WriterT w m) ( WriterT w n) s t Source #
Instance details Defined in Control.Lens.Zoom Methods zoom :: LensLike' ( Zoomed ( WriterT w m) c) t s -> WriterT w m c -> WriterT w n c Source #
( Monoid w, Zoom m n s t) => Zoom ( WriterT w m) ( WriterT w n) s t Source #
Instance details Defined in Control.Lens.Zoom Methods zoom :: LensLike' ( Zoomed ( WriterT w m) c) t s -> WriterT w m c -> WriterT w n c Source #
( Monoid w, Monad z) => Zoom ( RWST r w s z) ( RWST r w t z) s t Source #
Instance details 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 Source #
( Monoid w, Monad z) => Zoom ( RWST r w s z) ( RWST r w t z) s t Source #
Instance details 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 Source #

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

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

Instances

Instances details

type Zoomed ( MaybeT m) Source #
Instance details Defined in Control.Lens.Zoom type Zoomed ( MaybeT m) = FocusingMay ( Zoomed m)
type Zoomed ( ListT m) Source #
Instance details Defined in Control.Lens.Zoom type Zoomed ( ListT m) = FocusingOn [] ( Zoomed m)
type Zoomed ( IdentityT m) Source #
Instance details Defined in Control.Lens.Zoom type Zoomed ( IdentityT m) = Zoomed m
type Zoomed ( ExceptT e m) Source #
Instance details Defined in Control.Lens.Zoom type Zoomed ( ExceptT e m) = FocusingErr e ( Zoomed m)
type Zoomed ( FreeT f m) Source #
Instance details Defined in Control.Lens.Zoom type Zoomed ( FreeT f m) = FocusingFree f m ( Zoomed m)
type Zoomed ( ErrorT e m) Source #
Instance details Defined in Control.Lens.Zoom type Zoomed ( ErrorT e m) = FocusingErr e ( Zoomed m)
type Zoomed ( ReaderT e m) Source #
Instance details Defined in Control.Lens.Zoom type Zoomed ( ReaderT e m) = Zoomed m
type Zoomed ( StateT s z) Source #
Instance details Defined in Control.Lens.Zoom type Zoomed ( StateT s z) = Focusing z
type Zoomed ( StateT s z) Source #
Instance details Defined in Control.Lens.Zoom type Zoomed ( StateT s z) = Focusing z
type Zoomed ( WriterT w m) Source #
Instance details Defined in Control.Lens.Zoom type Zoomed ( WriterT w m) = FocusingPlus w ( Zoomed m)
type Zoomed ( WriterT w m) Source #
Instance details Defined in Control.Lens.Zoom type Zoomed ( WriterT w m) = FocusingPlus w ( Zoomed m)
type Zoomed ( RWST r w s z) Source #
Instance details Defined in Control.Lens.Zoom type Zoomed ( RWST r w s z) = FocusingWith w z
type Zoomed ( RWST r w s z) Source #
Instance details Defined in Control.Lens.Zoom type Zoomed ( RWST r w s z) = FocusingWith w z