| 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 | None |
| Language | Haskell98 |
Control.Lens.Equality
Description
- type Equality s t a b = forall p f. p a (f b) -> p s (f t)
- type Equality' s a = Equality s s a a
- type AnEquality s t a b = Identical a (Proxy b) a (Proxy b) -> Identical a (Proxy b) s (Proxy t)
- type AnEquality' s a = AnEquality s s a a
- runEq :: AnEquality s t a b -> Identical s t a b
- substEq :: AnEquality s t a b -> ((s ~ a, t ~ b) => r) -> r
- mapEq :: forall s t a b f. AnEquality s t a b -> f s -> f a
- fromEq :: AnEquality s t a b -> Equality b a t s
- simply :: (Optic' p f s a -> r) -> Optic' p f s a -> r
- simple :: Equality' a a
- data Identical a b s t where
Type Equality
type Equality s t a b = forall p f. p a (f b) -> p s (f t) Source
A witness that (a ~ s, b ~ t).
Note: Composition with an Equality is index-preserving.
type AnEquality s t a b = Identical a (Proxy b) a (Proxy b) -> Identical a (Proxy b) s (Proxy t) Source
When you see this as an argument to a function, it expects an Equality.
type AnEquality' s a = AnEquality s s a a Source
A Simple AnEquality.
runEq :: AnEquality s t a b -> Identical s t a b Source
Extract a witness of type Equality.
substEq :: AnEquality s t a b -> ((s ~ a, t ~ b) => r) -> r Source
Substituting types with Equality.
mapEq :: forall s t a b f. AnEquality s t a b -> f s -> f a Source
We can use Equality to do substitution into anything.
fromEq :: AnEquality s t a b -> Equality b a t s Source
Equality is symmetric.
simply :: (Optic' p f s a -> r) -> Optic' p f s a -> r Source
This is an adverb that can be used to modify many other Lens combinators to make them require
simple lenses, simple traversals, simple prisms or simple isos as input.