Copyright  (C) 201216 Edward Kmett 

License  BSDstyle (see the file LICENSE) 
Maintainer  Edward Kmett <ekmett@gmail.com> 
Stability  provisional 
Portability  Rank2Types 
Safe Haskell  Trustworthy 
Language  Haskell2010 
Synopsis
 type family Magnified (m :: Type > Type) :: Type > Type > Type
 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
 class (MonadState s m, MonadState t n) => Zoom m n s t  m > s, n > t, m t > n, n s > m where
 type family Zoomed (m :: Type > Type) :: Type > Type > Type
Documentation
type family Magnified (m :: Type > Type) :: Type > Type > Type Source #
This type family is used by Magnify
to describe the common effect type.
Instances
type Magnified (IdentityT m) Source #  
Defined in Control.Lens.Zoom  
type Magnified (ReaderT b m) Source #  
Defined in Control.Lens.Zoom  
type Magnified ((>) b :: Type > Type) Source #  
type Magnified (RWST a w s m) Source #  
Defined in Control.Lens.Zoom  
type Magnified (RWST a w s m) Source #  
Defined in Control.Lens.Zoom 
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
.
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 higherrank constraints make it easier to apply magnify
to a
Getter
in highlypolymorphic code.
magnify
::Getter
s a > (a > r) > s > rmagnify
::Monoid
r =>Fold
s a > (a > r) > s > r
magnify
::Monoid
w =>Getter
s t >RWS
t w st c >RWS
s w st cmagnify
:: (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 Source #  
Monad m => Magnify (ReaderT b m) (ReaderT a m) b a Source #  
Magnify ((>) b :: Type > Type) ((>) a :: Type > Type) b a Source # 

Defined in Control.Lens.Zoom  
(Monad m, Monoid w) => Magnify (RWST b w s m) (RWST a w s m) b a Source #  
(Monad m, Monoid w) => Magnify (RWST b w s m) (RWST a w s m) b a 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.
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 azoom
:: (Monad
m,Monoid
c) =>Traversal'
s t >StateT
t m c >StateT
s m czoom
:: (Monad
m,Monoid
w) =>Lens'
s t >RWST
r w t m c >RWST
r w s m czoom
:: (Monad
m,Monoid
w,Monoid
c) =>Traversal'
s t >RWST
r w t m c >RWST
r w s m czoom
:: (Monad
m,Monoid
w,Error
e) =>Lens'
s t >ErrorT
e (RWST
r w t m) c >ErrorT
e (RWST
r w s m) czoom
:: (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 Source #  
Zoom m n s t => Zoom (ListT m) (ListT n) s t Source #  
Zoom m n s t => Zoom (IdentityT m) (IdentityT n) s t Source #  
Zoom m n s t => Zoom (ExceptT e m) (ExceptT e n) s t Source #  
(Functor f, Zoom m n s t) => Zoom (FreeT f m) (FreeT f n) s t Source #  
(Error e, Zoom m n s t) => Zoom (ErrorT e m) (ErrorT e n) s t Source #  
Zoom m n s t => Zoom (ReaderT e m) (ReaderT e n) s t Source #  
Monad z => Zoom (StateT s z) (StateT t z) s t Source #  
Monad z => Zoom (StateT s z) (StateT t z) s t Source #  
(Monoid w, Zoom m n s t) => Zoom (WriterT w m) (WriterT w n) s t Source #  
(Monoid w, Zoom m n s t) => Zoom (WriterT w m) (WriterT w n) s t Source #  
(Monoid w, Monad z) => Zoom (RWST r w s z) (RWST r w t z) s t Source #  
(Monoid w, Monad z) => Zoom (RWST r w s z) (RWST r w t z) s t Source #  
type family Zoomed (m :: Type > Type) :: Type > Type > Type Source #
This type family is used by Zoom
to describe the common effect type.
Instances
type Zoomed (MaybeT m) Source #  
Defined in Control.Lens.Zoom  
type Zoomed (ListT m) Source #  
Defined in Control.Lens.Zoom  
type Zoomed (IdentityT m) Source #  
Defined in Control.Lens.Zoom  
type Zoomed (ExceptT e m) Source #  
Defined in Control.Lens.Zoom  
type Zoomed (FreeT f m) Source #  
Defined in Control.Lens.Zoom  
type Zoomed (ErrorT e m) Source #  
Defined in Control.Lens.Zoom  
type Zoomed (ReaderT e m) Source #  
Defined in Control.Lens.Zoom  
type Zoomed (StateT s z) Source #  
Defined in Control.Lens.Zoom  
type Zoomed (StateT s z) Source #  
Defined in Control.Lens.Zoom  
type Zoomed (WriterT w m) Source #  
Defined in Control.Lens.Zoom  
type Zoomed (WriterT w m) Source #  
Defined in Control.Lens.Zoom  
type Zoomed (RWST r w s z) Source #  
Defined in Control.Lens.Zoom  
type Zoomed (RWST r w s z) Source #  
Defined in Control.Lens.Zoom 