| Portability | Rank2Types |
|---|---|
| Stability | provisional |
| Maintainer | Edward Kmett <ekmett@gmail.com> |
| Safe Haskell | Safe-Inferred |
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 (Identity b) a (Identity b) -> Identical a (Identity b) s (Identity 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 :: 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 (Identity b) a (Identity b) -> Identical a (Identity b) s (Identity t)Source
When you see this as an argument to a function, it expects an Equality.
type AnEquality' s a = AnEquality s s a aSource
A Simple AnEquality.
runEq :: AnEquality s t a b -> Identical s t a bSource
Extract a witness of type Equality.
substEq :: AnEquality s t a b -> ((s ~ a, t ~ b) => r) -> rSource
Substituting types with Equality.
mapEq :: AnEquality s t a b -> f s -> f aSource
We can use Equality to do substitution into anything.
fromEq :: AnEquality s t a b -> Equality b a t sSource
Equality is symmetric.
simply :: (Optic' p f s a -> r) -> Optic' p f s a -> rSource
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.