| Portability | non-portable |
|---|---|
| Stability | provisional |
| Maintainer | Edward Kmett <ekmett@gmail.com> |
| Safe Haskell | None |
Control.Lens.Projection
Contents
Description
- type Projection a b c d = forall k f. (Projective k a d, Applicative f) => k (c -> f d) (a -> f a)
- class Projective k a d where
- projective :: (d -> a) -> (x -> y) -> k x y
- project :: Projective k a d => Overloaded (Project a d) f a a c d -> Overloaded k f a a c d
- by :: Project a d (d -> Identity d) (a -> Identity a) -> Getter d a
- data Project a d x y = Project (d -> a) (x -> y)
- projection :: (d -> a) -> (a -> Maybe c) -> Projection a b c d
- stereo :: Projective k a c => Project b c y z -> Project a b x y -> k x z
- mirror :: Projective k a c => Simple Iso a c -> Simple Projection a c
- type SimpleProjection a b = Projection a a b b
Documentation
type Projection a b c d = forall k f. (Projective k a d, Applicative f) => k (c -> f d) (a -> f a)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 | |
| (~ * a a', ~ * d d') => Projective (Project a d) a' d' |
project :: Projective k a d => Overloaded (Project a d) f a a c d -> Overloaded k f a a c dSource
Reflect a Projection.
by :: Project a d (d -> Identity d) (a -> Identity a) -> Getter d aSource
Turn a Projection around to get an embedding
A concrete Projection, suitable for storing in a container or extracting an embedding.
Constructors
| Project (d -> a) (x -> y) |
Instances
| (~ * a a', ~ * d d') => Projective (Project a d) a' d' |
projection :: (d -> a) -> (a -> Maybe c) -> Projection a b c dSource
Build a Projection
stereo :: Projective k a c => Project b c y z -> Project a b x y -> k x zSource
Compose projections.
mirror :: Projective k a c => Simple Iso a c -> Simple Projection a cSource
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 a b = Projection a a b bSource
typeSimpleProjection=SimpleProjection