| Portability | non-portable |
|---|---|
| Stability | provisional |
| Maintainer | Edward Kmett <ekmett@gmail.com> |
| Safe Haskell | Safe-Inferred |
Control.Lens.Projection
Contents
Description
- type Projection s t a b = forall k f. (Projective k s b, Applicative f) => k (a -> f b) (s -> f s)
- class Projective k a d where
- projective :: (d -> a) -> (x -> y) -> k x y
- project :: Projective k s b => Overloaded (Project s b) f s s a b -> Overloaded k f s s a b
- by :: Project s b (b -> Identity b) (s -> Identity s) -> Getter b s
- data Project s b x y = Project (b -> s) (x -> y)
- projection :: (b -> s) -> (s -> Maybe a) -> Projection s t a b
- stereo :: Projective k s a => Project t a y z -> Project s t x y -> k x z
- mirror :: Projective k s a => Simple Iso s a -> Simple Projection s a
- type SimpleProjection s a = Projection s s a a
Documentation
type Projection s t a b = forall k f. (Projective k s b, Applicative f) => k (a -> f b) (s -> f s)Source
A Projection is a Traversal that can also be turned around with by to obtain a Getter
class Projective k a d whereSource
Used to provide overloading of projections.
Methods
projective :: (d -> a) -> (x -> y) -> k x ySource
Instances
| Projective (->) a d | |
| (~ * s s', ~ * b b') => Projective (Project s b) s' b' |
project :: Projective k s b => Overloaded (Project s b) f s s a b -> Overloaded k f s s a bSource
Reflect a Projection.
by :: Project s b (b -> Identity b) (s -> Identity s) -> Getter b sSource
Turn a Projection around to get an embedding
A concrete Projection, suitable for storing in a container or extracting an embedding.
Constructors
| Project (b -> s) (x -> y) |
Instances
| (~ * s s', ~ * b b') => Projective (Project s b) s' b' |
projection :: (b -> s) -> (s -> Maybe a) -> Projection s t a bSource
Build a Projection
stereo :: Projective k s a => Project t a y z -> Project s t x y -> k x zSource
Compose projections.
mirror :: Projective k s a => Simple Iso s a -> Simple Projection s aSource
Convert an Iso to a Projection.
Ideally we would be able to use an Iso directly as a Projection, but this opens a can of worms.
Simple
type SimpleProjection s a = Projection s s a aSource
typeSimpleProjection=SimpleProjection