| Copyright | (C) 2012-16 Edward Kmett Michael Sloan |
|---|---|
| License | BSD-style (see the file LICENSE) |
| Maintainer | Edward Kmett <ekmett@gmail.com> |
| Stability | experimental |
| Portability | Rank2, MPTCs, fundeps |
| Safe Haskell | Trustworthy |
| Language | Haskell98 |
Control.Lens.Wrapped
Contents
Description
The Wrapped class provides similar functionality as Control.Newtype,
from the newtype package, but in a more convenient and efficient form.
There are a few functions from newtype that are not provided here, because
they can be done with the Iso directly:
Control.Newtype.overSumf ≡_UnwrappingSum%~f Control.Newtype.underSumf ≡_WrappingSum%~f Control.Newtype.overFSumf ≡mapping(_UnwrappingSum)%~f Control.Newtype.underFSumf ≡mapping(_WrappingSum)%~f
under can also be used with _Unwrapping to provide the equivalent of
Control.Newtype.under. Also, most use cases don't need full polymorphism,
so only the single constructor _Wrapping functions would be needed.
These equivalences aren't 100% honest, because newtype's operators
need to rely on two Newtype constraints. This means that the wrapper used
for the output is not necessarily the same as the input.
Synopsis
- class Wrapped s where
- _Unwrapped' :: Wrapped s => Iso' (Unwrapped s) s
- _Wrapping' :: Wrapped s => (Unwrapped s -> s) -> Iso' s (Unwrapped s)
- _Unwrapping' :: Wrapped s => (Unwrapped s -> s) -> Iso' (Unwrapped s) s
- class Wrapped s => Rewrapped (s :: *) (t :: *)
- class (Rewrapped s t, Rewrapped t s) => Rewrapping s t
- _Wrapped :: Rewrapping s t => Iso s t (Unwrapped s) (Unwrapped t)
- _Unwrapped :: Rewrapping s t => Iso (Unwrapped t) (Unwrapped s) t s
- _Wrapping :: Rewrapping s t => (Unwrapped s -> s) -> Iso s t (Unwrapped s) (Unwrapped t)
- _Unwrapping :: Rewrapping s t => (Unwrapped s -> s) -> Iso (Unwrapped t) (Unwrapped s) t s
- op :: Wrapped s => (Unwrapped s -> s) -> s -> Unwrapped s
- ala :: (Functor f, Rewrapping s t) => (Unwrapped s -> s) -> ((Unwrapped t -> t) -> f s) -> f (Unwrapped s)
- alaf :: (Functor f, Functor g, Rewrapping s t) => (Unwrapped s -> s) -> (f t -> g s) -> f (Unwrapped t) -> g (Unwrapped s)
- pattern Wrapped :: forall s. Rewrapped s s => Unwrapped s -> s
- pattern Unwrapped :: forall t. Rewrapped t t => t -> Unwrapped t
- _GWrapped' :: (Generic s, D1 d (C1 c (S1 s' (Rec0 a))) ~ Rep s, Unwrapped s ~ GUnwrapped (Rep s)) => Iso' s (Unwrapped s)
Wrapping and Unwrapping monomorphically
class Wrapped s where Source #
Wrapped provides isomorphisms to wrap and unwrap newtypes or
data types with one constructor.
Methods
_Wrapped' :: Iso' s (Unwrapped s) Source #
An isomorphism between s and a.
If your type has a Generic instance, _Wrapped' will default to _GWrapped',
and you can choose to not override it with your own definition.
_Wrapped' :: (Generic s, D1 d (C1 c (S1 s' (Rec0 a))) ~ Rep s, Unwrapped s ~ GUnwrapped (Rep s)) => Iso' s (Unwrapped s) Source #
An isomorphism between s and a.
If your type has a Generic instance, _Wrapped' will default to _GWrapped',
and you can choose to not override it with your own definition.
Instances
_Wrapping' :: Wrapped s => (Unwrapped s -> s) -> Iso' s (Unwrapped s) Source #
This is a convenient version of _Wrapped with an argument that's ignored.
The user supplied function is ignored, merely its type is used.
_Unwrapping' :: Wrapped s => (Unwrapped s -> s) -> Iso' (Unwrapped s) s Source #
This is a convenient version of _Wrapped with an argument that's ignored.
The user supplied function is ignored, merely its type is used.
Wrapping and unwrapping polymorphically
class Wrapped s => Rewrapped (s :: *) (t :: *) Source #
Instances
class (Rewrapped s t, Rewrapped t s) => Rewrapping s t Source #
Instances
| (Rewrapped s t, Rewrapped t s) => Rewrapping s t Source # | |
_Wrapped :: Rewrapping s t => Iso s t (Unwrapped s) (Unwrapped t) Source #
Work under a newtype wrapper.
>>>Const "hello" & _Wrapped %~ Prelude.length & getConst5
_Wrapped≡from_Unwrapped_Unwrapped≡from_Wrapped
_Unwrapped :: Rewrapping s t => Iso (Unwrapped t) (Unwrapped s) t s Source #
_Wrapping :: Rewrapping s t => (Unwrapped s -> s) -> Iso s t (Unwrapped s) (Unwrapped t) Source #
This is a convenient version of _Wrapped with an argument that's ignored.
The user supplied function is ignored, merely its types are used.
_Unwrapping :: Rewrapping s t => (Unwrapped s -> s) -> Iso (Unwrapped t) (Unwrapped s) t s Source #
This is a convenient version of _Unwrapped with an argument that's ignored.
The user supplied function is ignored, merely its types are used.
Operations
ala :: (Functor f, Rewrapping s t) => (Unwrapped s -> s) -> ((Unwrapped t -> t) -> f s) -> f (Unwrapped s) Source #
This combinator is based on ala from Conor McBride's work on Epigram.
As with _Wrapping, the user supplied function for the newtype is ignored.
>>>ala Sum foldMap [1,2,3,4]10
>>>ala All foldMap [True,True]True
>>>ala All foldMap [True,False]False
>>>ala Any foldMap [False,False]False
>>>ala Any foldMap [True,False]True
>>>ala Product foldMap [1,2,3,4]24
You may want to think of this combinator as having the following, simpler, type.
ala :: Rewrapping s t => (Unwrapped s -> s) -> ((Unwrapped t -> t) -> e -> s) -> e -> Unwrapped s
alaf :: (Functor f, Functor g, Rewrapping s t) => (Unwrapped s -> s) -> (f t -> g s) -> f (Unwrapped t) -> g (Unwrapped s) Source #
This combinator is based on ala' from Conor McBride's work on Epigram.
As with _Wrapping, the user supplied function for the newtype is ignored.
alaf :: Rewrapping s t => (Unwrapped s -> s) -> ((r -> t) -> e -> s) -> (r -> Unwrapped t) -> e -> Unwrapped s
>>>alaf Sum foldMap Prelude.length ["hello","world"]10