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	Haskell98

Control.Lens.At

Contents

At
Ixed
Contains

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

At IntSet Source
Methods at :: Index IntSet -> Lens' IntSet (Maybe (IxValue IntSet)) Source
At (Maybe a) Source
Methods at :: Index (Maybe a) -> Lens' (Maybe a) (Maybe (IxValue (Maybe a))) Source
At (IntMap a) Source
Methods at :: Index (IntMap a) -> Lens' (IntMap a) (Maybe (IxValue (IntMap a))) Source
Ord k => At (Set k) Source
Methods at :: Index (Set k) -> Lens' (Set k) (Maybe (IxValue (Set k))) Source
(Eq k, Hashable k) => At (HashSet k) Source
Methods at :: Index (HashSet k) -> Lens' (HashSet k) (Maybe (IxValue (HashSet k))) Source
Ord k => At (Map k a) Source
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
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

type Index ByteString = Int Source
type Index ByteString = Int64 Source
type Index IntSet = Int Source
type Index Text = Int64 Source
type Index Text = Int Source
type Index [a] = Int Source
type Index (Identity a) = () Source
type Index (Complex a) = Int Source
type Index (Maybe a) = () Source
type Index (IntMap a) = Int Source
type Index (Set a) = a Source
type Index (Tree a) = [Int] Source
type Index (Seq a) = Int Source
type Index (NonEmpty a) = Int Source
type Index (HashSet a) = a Source
type Index (Vector a) = Int Source
type Index (Vector a) = Int Source
type Index (Vector a) = Int Source
type Index (Vector a) = Int Source
type Index (e -> a) = e Source
type Index (a, b) = Int Source
type Index (UArray i e) = i Source
type Index (Array i e) = i Source
type Index (Map k a) = k Source
type Index (HashMap k a) = k Source
type Index (a, b, c) = Int Source
type Index (a, b, c, d) = Int Source
type Index (a, b, c, d, e) = Int Source
type Index (a, b, c, d, e, f) = Int Source
type Index (a, b, c, d, e, f, g) = Int Source
type Index (a, b, c, d, e, f, g, h) = Int Source
type Index (a, b, c, d, e, f, g, h, i) = Int Source

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

type IxValue ByteString = Word8 Source
type IxValue ByteString = Word8 Source
type IxValue IntSet = () Source
type IxValue Text = Char Source
type IxValue Text = Char Source
type IxValue [a] = a Source
type IxValue (Identity a) = a Source
type IxValue (Maybe a) = a Source
type IxValue (IntMap a) = a Source
type IxValue (Set k) = () Source
type IxValue (Tree a) = a Source
type IxValue (Seq a) = a Source
type IxValue (NonEmpty a) = a Source
type IxValue (HashSet k) = () Source
type IxValue (Vector a) = a Source
type IxValue (Vector a) = a Source
type IxValue (Vector a) = a Source
type IxValue (Vector a) = a Source
type IxValue (e -> a) = a Source
type IxValue (a, a2) = a Source	`ix` :: `Int` -> `Traversal'` (a,a) a
type IxValue (UArray i e) = e Source
type IxValue (Array i e) = e Source
type IxValue (Map k a) = a Source
type IxValue (HashMap k a) = a Source
type IxValue (a, a2, a3) = a Source	`ix` :: `Int` -> `Traversal'` (a,a,a) a
type IxValue (a, a2, a3, a4) = a Source	`ix` :: `Int` -> `Traversal'` (a,a,a,a) a
type IxValue (a, a2, a3, a4, a5) = a Source	`ix` :: `Int` -> `Traversal'` (a,a,a,a,a) a
type IxValue (a, a2, a3, a4, a5, a6) = a Source	`ix` :: `Int` -> `Traversal'` (a,a,a,a,a,a) a
type IxValue (a, a2, a3, a4, a5, a6, a7) = a Source	`ix` :: `Int` -> `Traversal'` (a,a,a,a,a,a,a) a
type IxValue (a, a2, a3, a4, a5, a6, a7, a8) = a Source	`ix` :: `Int` -> `Traversal'` (a,a,a,a,a,a,a,a) a
type IxValue (a, a2, a3, a4, a5, a6, a7, a8, a9) = a Source	`ix` :: `Int` -> `Traversal'` (a,a,a,a,a,a,a,a,a) a

class Ixed m where Source

This 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

This 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.

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

Instances

Ixed ByteString Source
Methods ix :: Index ByteString -> Traversal' ByteString (IxValue ByteString) Source
Ixed ByteString Source
Methods ix :: Index ByteString -> Traversal' ByteString (IxValue ByteString) Source
Ixed IntSet Source
Methods ix :: Index IntSet -> Traversal' IntSet (IxValue IntSet) Source
Ixed Text Source
Methods ix :: Index Text -> Traversal' Text (IxValue Text) Source
Ixed Text Source
Methods ix :: Index Text -> Traversal' Text (IxValue Text) Source
Ixed [a] Source
Methods ix :: Index [a] -> Traversal' [a] (IxValue [a]) Source
Ixed (Identity a) Source
Methods ix :: Index (Identity a) -> Traversal' (Identity a) (IxValue (Identity a)) Source
Ixed (Maybe a) Source
Methods ix :: Index (Maybe a) -> Traversal' (Maybe a) (IxValue (Maybe a)) Source
Ixed (IntMap a) Source
Methods ix :: Index (IntMap a) -> Traversal' (IntMap a) (IxValue (IntMap a)) Source
Ord k => Ixed (Set k) Source
Methods ix :: Index (Set k) -> Traversal' (Set k) (IxValue (Set k)) Source
Ixed (Tree a) Source
Methods ix :: Index (Tree a) -> Traversal' (Tree a) (IxValue (Tree a)) Source
Ixed (Seq a) Source
Methods ix :: Index (Seq a) -> Traversal' (Seq a) (IxValue (Seq a)) Source
Ixed (NonEmpty a) Source
Methods ix :: Index (NonEmpty a) -> Traversal' (NonEmpty a) (IxValue (NonEmpty a)) Source
(Eq k, Hashable k) => Ixed (HashSet k) Source
Methods ix :: Index (HashSet k) -> Traversal' (HashSet k) (IxValue (HashSet k)) Source
Ixed (Vector a) Source
Methods ix :: Index (Vector a) -> Traversal' (Vector a) (IxValue (Vector a)) Source
Unbox a => Ixed (Vector a) Source
Methods ix :: Index (Vector a) -> Traversal' (Vector a) (IxValue (Vector a)) Source
Storable a => Ixed (Vector a) Source
Methods ix :: Index (Vector a) -> Traversal' (Vector a) (IxValue (Vector a)) Source
Prim a => Ixed (Vector a) Source
Methods ix :: Index (Vector a) -> Traversal' (Vector a) (IxValue (Vector a)) Source
Eq e => Ixed (e -> a) Source
Methods ix :: Index (e -> a) -> Traversal' (e -> a) (IxValue (e -> a)) Source
(~) * a a2 => Ixed (a, a2) Source
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 `$` arr
Methods ix :: Index (UArray i e) -> Traversal' (UArray i e) (IxValue (UArray i e)) Source
Ix i => Ixed (Array i e) Source	arr `!` i ≡ arr `^.` `ix` i arr `//` [(i,e)] ≡ `ix` i `.~` e `$` arr
Methods ix :: Index (Array i e) -> Traversal' (Array i e) (IxValue (Array i e)) Source
Ord k => Ixed (Map k a) Source
Methods ix :: Index (Map k a) -> Traversal' (Map k a) (IxValue (Map k a)) Source
(Eq k, Hashable k) => Ixed (HashMap k a) Source
Methods ix :: Index (HashMap k a) -> Traversal' (HashMap k a) (IxValue (HashMap k a)) Source
((~) * a a2, (~) * a a3) => Ixed (a, a2, a3) Source
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
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
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
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
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
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
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

Contains IntSet Source
Methods contains :: Index IntSet -> Lens' IntSet Bool Source
Ord a => Contains (Set a) Source
Methods contains :: Index (Set a) -> Lens' (Set a) Bool Source
(Eq a, Hashable a) => Contains (HashSet a) Source
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]