Control.Lens.Indexed

Combinators for working with Indexed functions.

Documentation

class Indexable i k where

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

Methods

indexed :: ((i -> a) -> b) -> k a b

Build a function from an Indexed function

Instances

Indexable i (->)

~ * i j => Indexable i (Indexed j)

Using an equality witness to avoid potential overlapping instances and aid dispatch.

Indexed Functions

newtype Indexed i a b

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

Constructors

Indexed

Fields

withIndex :: (i -> a) -> b

Instances

~ * i j => Indexable i (Indexed j)

Using an equality witness to avoid potential overlapping instances and aid dispatch.

(<.>) :: Indexable (i, j) k => Indexed i b c -> Indexed j a b -> k a c

Composition of Indexed functions

Mnemonically, the < and > points to the fact that we want to preserve the indices.

(<.) :: Indexable i k => Indexed i b c -> (a -> b) -> k a c

Compose an Indexed function with a non-indexed function.

Mnemonically, the < points to the indexing we want to preserve.

(.>) :: Indexable i k => (b -> c) -> Indexed i a b -> k a c

Compose a non-indexed function with an Indexed function.

Mnemonically, the > points to the indexing we want to preserve.

icompose :: Indexable k r => (i -> j -> k) -> Indexed i b c -> Indexed j a b -> r a c

Composition of Indexed functions with a user supplied function for combining indices

reindexed :: Indexable j k => (i -> j) -> Indexed i a b -> k a b

Remap the index.

Indexing existing lenses, traversals, etc.

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

Transform an 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 t          -> IndexedFold Int s t
 indexing :: Getter s t        -> IndexedGetter Int s t a b