lens-1.4: Lenses, Folds and Traversals

PortabilityRank2Types
Stabilityprovisional
MaintainerEdward Kmett <ekmett@gmail.com>
Safe HaskellSafe-Infered

Data.Map.Lens

Description

 

Synopsis

Documentation

at :: Ord k => k -> SimpleLens (Map k v) (Maybe v)Source

This Lens can be used to read, write or delete the value associated with a key in a Map.

 ghci> Map.fromList [("hello",12)] ^.at "hello"
 Just 12
 at :: Ord k => k -> (Maybe v -> f (Maybe v)) -> Map k v -> f (Map k v)

traverseAt :: Ord k => k -> SimpleTraversal (Map k v) vSource

Traverse the value at a given key in a Map

 traverseAt :: (Applicative f, Ord k) => k -> (v -> f v) -> Map k v -> f (Map k v)
 traverseAt k = valueAt k . traverse

traverseAtMin :: SimpleTraversal (Map k v) vSource

Traverse the value at the minimum key in a Map

traverseAtMax :: SimpleTraversal (Map k v) vSource

Traverse the value at the maximum key in a Map