lens-3.8.5: Lenses, Folds and Traversals

Portabilitynon-portable
Stabilityexperimental
MaintainerEdward Kmett <ekmett@gmail.com>
Safe HaskellTrustworthy

Control.Lens.Internal.Indexed

Contents

Description

Internal implementation details for Indexed lens-likes

Synopsis

An Indexed Profunctor

newtype Indexed i a b Source

A function with access to a index. This constructor may be useful when you need to store an Indexable in a container to avoid ImpredicativeTypes. 

index :: Indexed i a b -> i -> a -> b

Constructors

Indexed 

Fields

runIndexed :: i -> a -> b
 

Instances

Classes

class (Choice p, Corepresentable p, Comonad (Corep p), Traversable (Corep p), Strong p, Representable p, Monad (Rep p), MonadFix (Rep p), Distributive (Rep p), ArrowLoop p, ArrowApply p, ArrowChoice p) => Conjoined p whereSource

This is a Profunctor that is both Corepresentable by f and Representable by g such that f is left adjoint to g. From this you can derive a lot of structure due to the preservation of limits and colimits.

Methods

distrib :: Functor f => p a b -> p (f a) (f b)Source

Conjoined is strong enough to let us distribute every Conjoined Profunctor over every Haskell Functor. This is effectively a generalization of fmap.

conjoined :: (p ~ (->) => q (a -> b) r) -> q (p a b) r -> q (p a b) rSource

This permits us to make a decision at an outermost point about whether or not we use an index.

Ideally any use of this function should be done in such a way so that you compute the same answer, but this cannot be enforced at the type level.

Instances

class Conjoined p => Indexable i p whereSource

This class permits overloading of function application for things that also admit a notion of a key or index.

Methods

indexed :: p a b -> i -> a -> bSource

Build a function from an indexed function.

Instances

Conjoined (->) => Indexable i (->) 
(Conjoined (Indexed j), ~ * i j) => Indexable i (Indexed j) 

Indexing

newtype Indexing f a Source

Applicative composition of State Int with a Functor, used by indexed.

Constructors

Indexing 

Fields

runIndexing :: Int -> (Int, f a)
 

Instances

indexing :: Indexable Int p => ((a -> Indexing f b) -> s -> Indexing f t) -> p a (f b) -> s -> f tSource

Transform a Traversal into an IndexedTraversal or a Fold into an IndexedFold, etc. 

 indexing :: Traversal s t a b -> IndexedTraversal Int s t a b
 indexing :: Prism s t a b     -> IndexedTraversal Int s t a b
 indexing :: Lens s t a b      -> IndexedLens Int  s t a b
 indexing :: Iso s t a b       -> IndexedLens Int s t a b
 indexing :: Fold s a          -> IndexedFold Int s a
 indexing :: Getter s a        -> IndexedGetter Int s a

indexing :: Indexable Int p => LensLike (Indexing f) s t a b -> Overloading p (->) f s t a b

64-bit Indexing

newtype Indexing64 f a Source

Applicative composition of State Int64 with a Functor, used by indexed64.

Constructors

Indexing64 

Fields

runIndexing64 :: Int64 -> (Int64, f a)
 

Instances

indexing64 :: Indexable Int64 p => ((a -> Indexing64 f b) -> s -> Indexing64 f t) -> p a (f b) -> s -> f tSource

Transform a Traversal into an IndexedTraversal or a Fold into an IndexedFold, etc.

This combinator is like indexing except that it handles large traversals and folds gracefully. 

 indexing64 :: Traversal s t a b -> IndexedTraversal Int64 s t a b
 indexing64 :: Prism s t a b     -> IndexedTraversal Int64 s t a b
 indexing64 :: Lens s t a b      -> IndexedLens Int64 s t a b
 indexing64 :: Iso s t a b       -> IndexedLens Int64 s t a b
 indexing64 :: Fold s a          -> IndexedFold Int64 s a
 indexing64 :: Getter s a        -> IndexedGetter Int64 s a

indexing64 :: Indexable Int64 p => LensLike (Indexing64 f) s t a b -> Overloading p (->) f s t a b