lens-5.0.1: Lenses, Folds and Traversals
Copyright (C) 2012-16 Edward Kmett
License BSD-style (see the file LICENSE)
Maintainer Edward Kmett <ekmett@gmail.com>
Stability experimental
Portability non-portable
Safe Haskell Trustworthy
Language Haskell2010

Control.Lens.At

Description

Synopsis

At

class Ixed m => At m where Source #

At provides a Lens that can be used to read, write or delete the value associated with a key in a Map -like container on an ad hoc basis.

An instance of At should satisfy: 

ix k ≡ at k . traverse

Methods

at :: Index m -> Lens' m ( Maybe ( IxValue m)) Source # 

>>> Map.fromList [(1,"world")] ^.at 1
Just "world"

>>> at 1 ?~ "hello" $ Map.empty
fromList [(1,"hello")]

Note: Map -like containers form a reasonable instance, but not Array -like ones, where you cannot satisfy the Lens laws.

Instances

Instances details
At IntSet Source #
Instance details

Defined in Control.Lens.At

Methods

at :: Index IntSet -> Lens' IntSet ( Maybe ( IxValue IntSet )) Source #

At ( Maybe a) Source #
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Defined in Control.Lens.At

Methods

at :: Index ( Maybe a) -> Lens' ( Maybe a) ( Maybe ( IxValue ( Maybe a))) Source #

At ( IntMap a) Source #
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Defined in Control.Lens.At

Methods

at :: Index ( IntMap a) -> Lens' ( IntMap a) ( Maybe ( IxValue ( IntMap a))) Source #

Ord k => At ( Set k) Source #
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Defined in Control.Lens.At

Methods

at :: Index ( Set k) -> Lens' ( Set k) ( Maybe ( IxValue ( Set k))) Source #

( Eq k, Hashable k) => At ( HashSet k) Source #
Instance details

Defined in Control.Lens.At

Methods

at :: Index ( HashSet k) -> Lens' ( HashSet k) ( Maybe ( IxValue ( HashSet k))) Source #

Ord k => At ( Map k a) Source #
Instance details

Defined in Control.Lens.At

Methods

at :: Index ( Map k a) -> Lens' ( Map k a) ( Maybe ( IxValue ( Map k a))) Source #

( Eq k, Hashable k) => At ( HashMap k a) Source #
Instance details

Defined in Control.Lens.At

Methods

at :: Index ( HashMap k a) -> Lens' ( HashMap k a) ( Maybe ( IxValue ( HashMap k a))) Source #

sans :: At m => Index m -> m -> m Source #

Delete the value associated with a key in a Map -like container 

sans k = at k .~ Nothing

iat :: At m => Index m -> IndexedLens' ( Index m) m ( Maybe ( IxValue m)) Source #

An indexed version of at . 

>>> Map.fromList [(1,"world")] ^@. iat 1
(1,Just "world")

>>> iat 1 %@~ (\i x -> if odd i then Just "hello" else Nothing) $ Map.empty
fromList [(1,"hello")]

>>> iat 2 %@~ (\i x -> if odd i then Just "hello" else Nothing) $ Map.empty
fromList []

Ixed

type family Index (s :: *) :: * Source #

Instances

Instances details
type Index ByteString Source #
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Defined in Control.Lens.At

type Index ByteString = Int64
type Index ByteString Source #
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Defined in Control.Lens.At

type Index ByteString = Int
type Index IntSet Source #
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type Index IntSet = Int
type Index Text Source #
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type Index Text = Int64
type Index Text Source #
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type Index Text = Int
type Index [a] Source #
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type Index [a] = Int
type Index ( Maybe a) Source #
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type Index ( Maybe a) = ()
type Index ( Complex a) Source #
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type Index ( Complex a) = Int
type Index ( Identity a) Source #
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type Index ( Identity a) = ()
type Index ( NonEmpty a) Source #
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type Index ( NonEmpty a) = Int
type Index ( IntMap a) Source #
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type Index ( IntMap a) = Int
type Index ( Tree a) Source #
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type Index ( Tree a) = [ Int ]
type Index ( Seq a) Source #
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type Index ( Seq a) = Int
type Index ( Set a) Source #
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type Index ( Set a) = a
type Index ( HashSet a) Source #
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type Index ( HashSet a) = a
type Index ( Vector a) Source #
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type Index ( Vector a) = Int
type Index ( Vector a) Source #
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type Index ( Vector a) = Int
type Index ( Vector a) Source #
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Defined in Control.Lens.At

type Index ( Vector a) = Int
type Index ( Vector a) Source #
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Defined in Control.Lens.At

type Index ( Vector a) = Int
type Index (e -> a) Source #
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type Index (e -> a) = e
type Index (a, b) Source #
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Defined in Control.Lens.At

type Index (a, b) = Int
type Index ( UArray i e) Source #
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Defined in Control.Lens.At

type Index ( UArray i e) = i
type Index ( Array i e) Source #
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type Index ( Array i e) = i
type Index ( Map k a) Source #
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type Index ( Map k a) = k
type Index ( HashMap k a) Source #
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Defined in Control.Lens.At

type Index ( HashMap k a) = k
type Index (a, b, c) Source #
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Defined in Control.Lens.At

type Index (a, b, c) = Int
type Index (a, b, c, d) Source #
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Defined in Control.Lens.At

type Index (a, b, c, d) = Int
type Index (a, b, c, d, e) Source #
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Defined in Control.Lens.At

type Index (a, b, c, d, e) = Int
type Index (a, b, c, d, e, f) Source #
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Defined in Control.Lens.At

type Index (a, b, c, d, e, f) = Int
type Index (a, b, c, d, e, f, g) Source #
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Defined in Control.Lens.At

type Index (a, b, c, d, e, f, g) = Int
type Index (a, b, c, d, e, f, g, h) Source #
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Defined in Control.Lens.At

type Index (a, b, c, d, e, f, g, h) = Int
type Index (a, b, c, d, e, f, g, h, i) Source #
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Defined in Control.Lens.At

type Index (a, b, c, d, e, f, g, h, i) = Int

type family IxValue (m :: *) :: * Source #

This provides a common notion of a value at an index that is shared by both Ixed and At .

Instances

Instances details
type IxValue ByteString Source #
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Defined in Control.Lens.At

type IxValue ByteString = Word8
type IxValue ByteString Source #
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Defined in Control.Lens.At

type IxValue ByteString = Word8
type IxValue IntSet Source #
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Defined in Control.Lens.At

type IxValue IntSet = ()
type IxValue Text Source #
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Defined in Control.Lens.At

type IxValue Text = Char
type IxValue Text Source #
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type IxValue Text = Char
type IxValue [a] Source #
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type IxValue [a] = a
type IxValue ( Maybe a) Source #
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type IxValue ( Maybe a) = a
type IxValue ( Identity a) Source #
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Defined in Control.Lens.At

type IxValue ( Identity a) = a
type IxValue ( NonEmpty a) Source #
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type IxValue ( NonEmpty a) = a
type IxValue ( IntMap a) Source #
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Defined in Control.Lens.At

type IxValue ( IntMap a) = a
type IxValue ( Tree a) Source #
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Defined in Control.Lens.At

type IxValue ( Tree a) = a
type IxValue ( Seq a) Source #
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Defined in Control.Lens.At

type IxValue ( Seq a) = a
type IxValue ( Set k) Source #
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type IxValue ( Set k) = ()
type IxValue ( HashSet k) Source #
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Defined in Control.Lens.At

type IxValue ( HashSet k) = ()
type IxValue ( Vector a) Source #
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Defined in Control.Lens.At

type IxValue ( Vector a) = a
type IxValue ( Vector a) Source #
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Defined in Control.Lens.At

type IxValue ( Vector a) = a
type IxValue ( Vector a) Source #
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Defined in Control.Lens.At

type IxValue ( Vector a) = a
type IxValue ( Vector a) Source #
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type IxValue ( Vector a) = a
type IxValue (e -> a) Source #
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Defined in Control.Lens.At

type IxValue (e -> a) = a
type IxValue (a, a2) Source # 
ix :: Int -> Traversal' (a,a) a
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Defined in Control.Lens.At

type IxValue (a, a2) = a
type IxValue ( UArray i e) Source #
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Defined in Control.Lens.At

type IxValue ( UArray i e) = e
type IxValue ( Array i e) Source #
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Defined in Control.Lens.At

type IxValue ( Array i e) = e
type IxValue ( Map k a) Source #
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Defined in Control.Lens.At

type IxValue ( Map k a) = a
type IxValue ( HashMap k a) Source #
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Defined in Control.Lens.At

type IxValue ( HashMap k a) = a
type IxValue (a, a2, a3) Source # 
ix :: Int -> Traversal' (a,a,a) a
Instance details

Defined in Control.Lens.At

type IxValue (a, a2, a3) = a
type IxValue (a, a2, a3, a4) Source # 
ix :: Int -> Traversal' (a,a,a,a) a
Instance details

Defined in Control.Lens.At

type IxValue (a, a2, a3, a4) = a
type IxValue (a, a2, a3, a4, a5) Source # 
ix :: Int -> Traversal' (a,a,a,a,a) a
Instance details

Defined in Control.Lens.At

type IxValue (a, a2, a3, a4, a5) = a
type IxValue (a, a2, a3, a4, a5, a6) Source # 
ix :: Int -> Traversal' (a,a,a,a,a,a) a
Instance details

Defined in Control.Lens.At

type IxValue (a, a2, a3, a4, a5, a6) = a
type IxValue (a, a2, a3, a4, a5, a6, a7) Source # 
ix :: Int -> Traversal' (a,a,a,a,a,a,a) a
Instance details

Defined in Control.Lens.At

type IxValue (a, a2, a3, a4, a5, a6, a7) = a
type IxValue (a, a2, a3, a4, a5, a6, a7, a8) Source # 
ix :: Int -> Traversal' (a,a,a,a,a,a,a,a) a
Instance details

Defined in Control.Lens.At

type IxValue (a, a2, a3, a4, a5, a6, a7, a8) = a
type IxValue (a, a2, a3, a4, a5, a6, a7, a8, a9) Source # 
ix :: Int -> Traversal' (a,a,a,a,a,a,a,a,a) a
Instance details

Defined in Control.Lens.At

type IxValue (a, a2, a3, a4, a5, a6, a7, a8, a9) = a

class Ixed m where Source #

Provides a simple Traversal lets you traverse the value at a given key in a Map or element at an ordinal position in a list or Seq .

Minimal complete definition

Nothing

Methods

ix :: Index m -> Traversal' m ( IxValue m) Source #

NB: Setting the value of this Traversal will only set the value in at if it is already present.

If you want to be able to insert missing values, you want at . 

>>> Seq.fromList [a,b,c,d] & ix 2 %~ f
fromList [a,b,f c,d]

>>> Seq.fromList [a,b,c,d] & ix 2 .~ e
fromList [a,b,e,d]

>>> Seq.fromList [a,b,c,d] ^? ix 2
Just c

>>> Seq.fromList [] ^? ix 2
Nothing

default ix :: At m => Index m -> Traversal' m ( IxValue m) Source #

Instances

Instances details
Ixed ByteString Source #
Instance details

Defined in Control.Lens.At

Methods

ix :: Index ByteString -> Traversal' ByteString ( IxValue ByteString ) Source #

Ixed ByteString Source #
Instance details

Defined in Control.Lens.At

Methods

ix :: Index ByteString -> Traversal' ByteString ( IxValue ByteString ) Source #

Ixed IntSet Source #
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Defined in Control.Lens.At

Methods

ix :: Index IntSet -> Traversal' IntSet ( IxValue IntSet ) Source #

Ixed Text Source #
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Defined in Control.Lens.At

Methods

ix :: Index Text -> Traversal' Text ( IxValue Text ) Source #

Ixed Text Source #
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Defined in Control.Lens.At

Methods

ix :: Index Text -> Traversal' Text ( IxValue Text ) Source #

Ixed [a] Source #
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Defined in Control.Lens.At

Methods

ix :: Index [a] -> Traversal' [a] ( IxValue [a]) Source #

Ixed ( Maybe a) Source #
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Defined in Control.Lens.At

Methods

ix :: Index ( Maybe a) -> Traversal' ( Maybe a) ( IxValue ( Maybe a)) Source #

Ixed ( Identity a) Source #
Instance details

Defined in Control.Lens.At

Methods

ix :: Index ( Identity a) -> Traversal' ( Identity a) ( IxValue ( Identity a)) Source #

Ixed ( NonEmpty a) Source #
Instance details

Defined in Control.Lens.At

Methods

ix :: Index ( NonEmpty a) -> Traversal' ( NonEmpty a) ( IxValue ( NonEmpty a)) Source #

Ixed ( IntMap a) Source #
Instance details

Defined in Control.Lens.At

Methods

ix :: Index ( IntMap a) -> Traversal' ( IntMap a) ( IxValue ( IntMap a)) Source #

Ixed ( Tree a) Source #
Instance details

Defined in Control.Lens.At

Methods

ix :: Index ( Tree a) -> Traversal' ( Tree a) ( IxValue ( Tree a)) Source #

Ixed ( Seq a) Source #
Instance details

Defined in Control.Lens.At

Methods

ix :: Index ( Seq a) -> Traversal' ( Seq a) ( IxValue ( Seq a)) Source #

Ord k => Ixed ( Set k) Source #
Instance details

Defined in Control.Lens.At

Methods

ix :: Index ( Set k) -> Traversal' ( Set k) ( IxValue ( Set k)) Source #

( Eq k, Hashable k) => Ixed ( HashSet k) Source #
Instance details

Defined in Control.Lens.At

Methods

ix :: Index ( HashSet k) -> Traversal' ( HashSet k) ( IxValue ( HashSet k)) Source #

Unbox a => Ixed ( Vector a) Source #
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Defined in Control.Lens.At

Methods

ix :: Index ( Vector a) -> Traversal' ( Vector a) ( IxValue ( Vector a)) Source #

Storable a => Ixed ( Vector a) Source #
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Defined in Control.Lens.At

Methods

ix :: Index ( Vector a) -> Traversal' ( Vector a) ( IxValue ( Vector a)) Source #

Prim a => Ixed ( Vector a) Source #
Instance details

Defined in Control.Lens.At

Methods

ix :: Index ( Vector a) -> Traversal' ( Vector a) ( IxValue ( Vector a)) Source #

Ixed ( Vector a) Source #
Instance details

Defined in Control.Lens.At

Methods

ix :: Index ( Vector a) -> Traversal' ( Vector a) ( IxValue ( Vector a)) Source #

Eq e => Ixed (e -> a) Source #
Instance details

Defined in Control.Lens.At

Methods

ix :: Index (e -> a) -> Traversal' (e -> a) ( IxValue (e -> a)) Source #

a ~ a2 => Ixed (a, a2) Source #
Instance details

Defined in Control.Lens.At

Methods

ix :: Index (a, a2) -> Traversal' (a, a2) ( IxValue (a, a2)) Source #

( IArray UArray e, Ix i) => Ixed ( UArray i e) Source # 
arr ! i ≡ arr ^. ix i
arr // [(i,e)] ≡ ix i .~ e $ arr
Instance details

Defined in Control.Lens.At

Methods

ix :: Index ( UArray i e) -> Traversal' ( UArray i e) ( IxValue ( UArray i e)) Source #

Ix i => Ixed ( Array i e) Source # 
arr ! i ≡ arr ^. ix i
arr // [(i,e)] ≡ ix i .~ e $ arr
Instance details

Defined in Control.Lens.At

Methods

ix :: Index ( Array i e) -> Traversal' ( Array i e) ( IxValue ( Array i e)) Source #

Ord k => Ixed ( Map k a) Source #
Instance details

Defined in Control.Lens.At

Methods

ix :: Index ( Map k a) -> Traversal' ( Map k a) ( IxValue ( Map k a)) Source #

( Eq k, Hashable k) => Ixed ( HashMap k a) Source #
Instance details

Defined in Control.Lens.At

Methods

ix :: Index ( HashMap k a) -> Traversal' ( HashMap k a) ( IxValue ( HashMap k a)) Source #

(a ~ a2, a ~ a3) => Ixed (a, a2, a3) Source #
Instance details

Defined in Control.Lens.At

Methods

ix :: Index (a, a2, a3) -> Traversal' (a, a2, a3) ( IxValue (a, a2, a3)) Source #

(a ~ a2, a ~ a3, a ~ a4) => Ixed (a, a2, a3, a4) Source #
Instance details

Defined in Control.Lens.At

Methods

ix :: Index (a, a2, a3, a4) -> Traversal' (a, a2, a3, a4) ( IxValue (a, a2, a3, a4)) Source #

(a ~ a2, a ~ a3, a ~ a4, a ~ a5) => Ixed (a, a2, a3, a4, a5) Source #
Instance details

Defined in Control.Lens.At

Methods

ix :: Index (a, a2, a3, a4, a5) -> Traversal' (a, a2, a3, a4, a5) ( IxValue (a, a2, a3, a4, a5)) Source #

(a ~ a2, a ~ a3, a ~ a4, a ~ a5, a ~ a6) => Ixed (a, a2, a3, a4, a5, a6) Source #
Instance details

Defined in Control.Lens.At

Methods

ix :: Index (a, a2, a3, a4, a5, a6) -> Traversal' (a, a2, a3, a4, a5, a6) ( IxValue (a, a2, a3, a4, a5, a6)) Source #

(a ~ a2, a ~ a3, a ~ a4, a ~ a5, a ~ a6, a ~ a7) => Ixed (a, a2, a3, a4, a5, a6, a7) Source #
Instance details

Defined in Control.Lens.At

Methods

ix :: Index (a, a2, a3, a4, a5, a6, a7) -> Traversal' (a, a2, a3, a4, a5, a6, a7) ( IxValue (a, a2, a3, a4, a5, a6, a7)) Source #

(a ~ a2, a ~ a3, a ~ a4, a ~ a5, a ~ a6, a ~ a7, a ~ a8) => Ixed (a, a2, a3, a4, a5, a6, a7, a8) Source #
Instance details

Defined in Control.Lens.At

Methods

ix :: Index (a, a2, a3, a4, a5, a6, a7, a8) -> Traversal' (a, a2, a3, a4, a5, a6, a7, a8) ( IxValue (a, a2, a3, a4, a5, a6, a7, a8)) Source #

(a ~ a2, a ~ a3, a ~ a4, a ~ a5, a ~ a6, a ~ a7, a ~ a8, a ~ a9) => Ixed (a, a2, a3, a4, a5, a6, a7, a8, a9) Source #
Instance details

Defined in Control.Lens.At

Methods

ix :: Index (a, a2, a3, a4, a5, a6, a7, a8, a9) -> Traversal' (a, a2, a3, a4, a5, a6, a7, a8, a9) ( IxValue (a, a2, a3, a4, a5, a6, a7, a8, a9)) Source #

ixAt :: At m => Index m -> Traversal' m ( IxValue m) Source #

A definition of ix for types with an At instance. This is the default if you don't specify a definition for ix .

iix :: Ixed m => Index m -> IndexedTraversal' ( Index m) m ( IxValue m) Source #

An indexed version of ix . 

>>> Seq.fromList [a,b,c,d] & iix 2 %@~ f'
fromList [a,b,f' 2 c,d]

>>> Seq.fromList [a,b,c,d] & iix 2 .@~ h
fromList [a,b,h 2,d]

>>> Seq.fromList [a,b,c,d] ^@? iix 2
Just (2,c)

>>> Seq.fromList [] ^@? iix 2
Nothing

Contains

class Contains m where Source #

This class provides a simple Lens that lets you view (and modify) information about whether or not a container contains a given Index .

Methods

contains :: Index m -> Lens' m Bool Source # 

>>> IntSet.fromList [1,2,3,4] ^. contains 3
True

>>> IntSet.fromList [1,2,3,4] ^. contains 5
False

>>> IntSet.fromList [1,2,3,4] & contains 3 .~ False
fromList [1,2,4]

Instances

Instances details
Contains IntSet Source #
Instance details

Defined in Control.Lens.At

Methods

contains :: Index IntSet -> Lens' IntSet Bool Source #

Ord a => Contains ( Set a) Source #
Instance details

Defined in Control.Lens.At

Methods

contains :: Index ( Set a) -> Lens' ( Set a) Bool Source #

( Eq a, Hashable a) => Contains ( HashSet a) Source #
Instance details

Defined in Control.Lens.At

Methods

contains :: Index ( HashSet a) -> Lens' ( HashSet a) Bool Source #

icontains :: Contains m => Index m -> IndexedLens' ( Index m) m Bool Source #

An indexed version of contains . 

>>> IntSet.fromList [1,2,3,4] ^@. icontains 3
(3,True)

>>> IntSet.fromList [1,2,3,4] ^@. icontains 5
(5,False)

>>> IntSet.fromList [1,2,3,4] & icontains 3 %@~ \i x -> if odd i then not x else x
fromList [1,2,4]

>>> IntSet.fromList [1,2,3,4] & icontains 3 %@~ \i x -> if even i then not x else x
fromList [1,2,3,4]