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

class Ixed m => At m where
- at :: Index m -> Lens' m (Maybe (IxValue m))
sans :: At m => Index m -> m -> m
iat :: At m => Index m -> IndexedLens' (Index m) m (Maybe (IxValue m))
type family Index (s :: *) :: *
type family IxValue (m :: *) :: *
class Ixed m where
- ix :: Index m -> Traversal' m (IxValue m)
ixAt :: At m => Index m -> Traversal' m (IxValue m)
iix :: Ixed m => Index m -> IndexedTraversal' (Index m) m (IxValue m)
class Contains m where
- contains :: Index m -> Lens' m Bool
icontains :: Contains m => Index m -> IndexedLens' (Index m) m Bool

At

class Ixed m => At m where #

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)) #

>>> 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 #
Instance details Defined in Control.Lens.At Methods at :: Index IntSet -> Lens' IntSet (Maybe (IxValue IntSet)) #
At (Maybe a) #
Instance details Defined in Control.Lens.At Methods at :: Index (Maybe a) -> Lens' (Maybe a) (Maybe (IxValue (Maybe a))) #
At (IntMap a) #
Instance details Defined in Control.Lens.At Methods at :: Index (IntMap a) -> Lens' (IntMap a) (Maybe (IxValue (IntMap a))) #
Ord k => At (Set k) #
Instance details Defined in Control.Lens.At Methods at :: Index (Set k) -> Lens' (Set k) (Maybe (IxValue (Set k))) #
(Eq k, Hashable k) => At (HashSet k) #
Instance details Defined in Control.Lens.At Methods at :: Index (HashSet k) -> Lens' (HashSet k) (Maybe (IxValue (HashSet k))) #
Ord k => At (Map k a) #
Instance details Defined in Control.Lens.At Methods at :: Index (Map k a) -> Lens' (Map k a) (Maybe (IxValue (Map k a))) #
(Eq k, Hashable k) => At (HashMap k a) #
Instance details Defined in Control.Lens.At Methods at :: Index (HashMap k a) -> Lens' (HashMap k a) (Maybe (IxValue (HashMap k a))) #

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

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)) #

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 :: *) :: * #

Instances

type Index ByteString #
Instance details Defined in Control.Lens.At type Index ByteString = Int64
type Index ByteString #
Instance details Defined in Control.Lens.At type Index ByteString = Int
type Index IntSet #
Instance details Defined in Control.Lens.At type Index IntSet = Int
type Index Text #
Instance details Defined in Control.Lens.At type Index Text = Int64
type Index Text #
Instance details Defined in Control.Lens.At type Index Text = Int
type Index [a] #
Instance details Defined in Control.Lens.At type Index [a] = Int
type Index (Maybe a) #
Instance details Defined in Control.Lens.At type Index (Maybe a) = ()
type Index (Complex a) #
Instance details Defined in Control.Lens.At type Index (Complex a) = Int
type Index (Identity a) #
Instance details Defined in Control.Lens.At type Index (Identity a) = ()
type Index (NonEmpty a) #
Instance details Defined in Control.Lens.At type Index (NonEmpty a) = Int
type Index (IntMap a) #
Instance details Defined in Control.Lens.At type Index (IntMap a) = Int
type Index (Tree a) #
Instance details Defined in Control.Lens.At type Index (Tree a) = [Int]
type Index (Seq a) #
Instance details Defined in Control.Lens.At type Index (Seq a) = Int
type Index (Set a) #
Instance details Defined in Control.Lens.At type Index (Set a) = a
type Index (HashSet a) #
Instance details Defined in Control.Lens.At type Index (HashSet a) = a
type Index (Vector a) #
Instance details Defined in Control.Lens.At type Index (Vector a) = Int
type Index (Vector a) #
Instance details Defined in Control.Lens.At type Index (Vector a) = Int
type Index (Vector a) #
Instance details Defined in Control.Lens.At type Index (Vector a) = Int
type Index (Vector a) #
Instance details Defined in Control.Lens.At type Index (Vector a) = Int
type Index (e -> a) #
Instance details Defined in Control.Lens.At type Index (e -> a) = e
type Index (a, b) #
Instance details Defined in Control.Lens.At type Index (a, b) = Int
type Index (UArray i e) #
Instance details Defined in Control.Lens.At type Index (UArray i e) = i
type Index (Array i e) #
Instance details Defined in Control.Lens.At type Index (Array i e) = i
type Index (Map k a) #
Instance details Defined in Control.Lens.At type Index (Map k a) = k
type Index (HashMap k a) #
Instance details Defined in Control.Lens.At type Index (HashMap k a) = k
type Index (a, b, c) #
Instance details Defined in Control.Lens.At type Index (a, b, c) = Int
type Index (a, b, c, d) #
Instance details Defined in Control.Lens.At type Index (a, b, c, d) = Int
type Index (a, b, c, d, e) #
Instance details Defined in Control.Lens.At type Index (a, b, c, d, e) = Int
type Index (a, b, c, d, e, f) #
Instance details Defined in Control.Lens.At type Index (a, b, c, d, e, f) = Int
type Index (a, b, c, d, e, f, g) #
Instance details 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) #
Instance details 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) #
Instance details Defined in Control.Lens.At type Index (a, b, c, d, e, f, g, h, i) = Int

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

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

Instances

type IxValue ByteString #
Instance details Defined in Control.Lens.At type IxValue ByteString = Word8
type IxValue ByteString #
Instance details Defined in Control.Lens.At type IxValue ByteString = Word8
type IxValue IntSet #
Instance details Defined in Control.Lens.At type IxValue IntSet = ()
type IxValue Text #
Instance details Defined in Control.Lens.At type IxValue Text = Char
type IxValue Text #
Instance details Defined in Control.Lens.At type IxValue Text = Char
type IxValue [a] #
Instance details Defined in Control.Lens.At type IxValue [a] = a
type IxValue (Maybe a) #
Instance details Defined in Control.Lens.At type IxValue (Maybe a) = a
type IxValue (Identity a) #
Instance details Defined in Control.Lens.At type IxValue (Identity a) = a
type IxValue (NonEmpty a) #
Instance details Defined in Control.Lens.At type IxValue (NonEmpty a) = a
type IxValue (IntMap a) #
Instance details Defined in Control.Lens.At type IxValue (IntMap a) = a
type IxValue (Tree a) #
Instance details Defined in Control.Lens.At type IxValue (Tree a) = a
type IxValue (Seq a) #
Instance details Defined in Control.Lens.At type IxValue (Seq a) = a
type IxValue (Set k) #
Instance details Defined in Control.Lens.At type IxValue (Set k) = ()
type IxValue (HashSet k) #
Instance details Defined in Control.Lens.At type IxValue (HashSet k) = ()
type IxValue (Vector a) #
Instance details Defined in Control.Lens.At type IxValue (Vector a) = a
type IxValue (Vector a) #
Instance details Defined in Control.Lens.At type IxValue (Vector a) = a
type IxValue (Vector a) #
Instance details Defined in Control.Lens.At type IxValue (Vector a) = a
type IxValue (Vector a) #
Instance details Defined in Control.Lens.At type IxValue (Vector a) = a
type IxValue (e -> a) #
Instance details Defined in Control.Lens.At type IxValue (e -> a) = a
type IxValue (a, a2) #	`ix` :: `Int` -> `Traversal'` (a,a) a
Instance details Defined in Control.Lens.At type IxValue (a, a2) = a
type IxValue (UArray i e) #
Instance details Defined in Control.Lens.At type IxValue (UArray i e) = e
type IxValue (Array i e) #
Instance details Defined in Control.Lens.At type IxValue (Array i e) = e
type IxValue (Map k a) #
Instance details Defined in Control.Lens.At type IxValue (Map k a) = a
type IxValue (HashMap k a) #
Instance details Defined in Control.Lens.At type IxValue (HashMap k a) = a
type IxValue (a, a2, a3) #	`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) #	`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) #	`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) #	`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) #	`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) #	`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) #	`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 #

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) #

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

ix :: (Applicative f, At m) => Index m -> LensLike' f m (IxValue m) #

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 #
Instance details Defined in Control.Lens.At Methods ix :: Index ByteString -> Traversal' ByteString (IxValue ByteString) #
Ixed ByteString #
Instance details Defined in Control.Lens.At Methods ix :: Index ByteString -> Traversal' ByteString (IxValue ByteString) #
Ixed IntSet #
Instance details Defined in Control.Lens.At Methods ix :: Index IntSet -> Traversal' IntSet (IxValue IntSet) #
Ixed Text #
Instance details Defined in Control.Lens.At Methods ix :: Index Text -> Traversal' Text (IxValue Text) #
Ixed Text #
Instance details Defined in Control.Lens.At Methods ix :: Index Text -> Traversal' Text (IxValue Text) #
Ixed [a] #
Instance details Defined in Control.Lens.At Methods ix :: Index [a] -> Traversal' [a] (IxValue [a]) #
Ixed (Maybe a) #
Instance details Defined in Control.Lens.At Methods ix :: Index (Maybe a) -> Traversal' (Maybe a) (IxValue (Maybe a)) #
Ixed (Identity a) #
Instance details Defined in Control.Lens.At Methods ix :: Index (Identity a) -> Traversal' (Identity a) (IxValue (Identity a)) #
Ixed (NonEmpty a) #
Instance details Defined in Control.Lens.At Methods ix :: Index (NonEmpty a) -> Traversal' (NonEmpty a) (IxValue (NonEmpty a)) #
Ixed (IntMap a) #
Instance details Defined in Control.Lens.At Methods ix :: Index (IntMap a) -> Traversal' (IntMap a) (IxValue (IntMap a)) #
Ixed (Tree a) #
Instance details Defined in Control.Lens.At Methods ix :: Index (Tree a) -> Traversal' (Tree a) (IxValue (Tree a)) #
Ixed (Seq a) #
Instance details Defined in Control.Lens.At Methods ix :: Index (Seq a) -> Traversal' (Seq a) (IxValue (Seq a)) #
Ord k => Ixed (Set k) #
Instance details Defined in Control.Lens.At Methods ix :: Index (Set k) -> Traversal' (Set k) (IxValue (Set k)) #
(Eq k, Hashable k) => Ixed (HashSet k) #
Instance details Defined in Control.Lens.At Methods ix :: Index (HashSet k) -> Traversal' (HashSet k) (IxValue (HashSet k)) #
Unbox a => Ixed (Vector a) #
Instance details Defined in Control.Lens.At Methods ix :: Index (Vector a) -> Traversal' (Vector a) (IxValue (Vector a)) #
Storable a => Ixed (Vector a) #
Instance details Defined in Control.Lens.At Methods ix :: Index (Vector a) -> Traversal' (Vector a) (IxValue (Vector a)) #
Prim a => Ixed (Vector a) #
Instance details Defined in Control.Lens.At Methods ix :: Index (Vector a) -> Traversal' (Vector a) (IxValue (Vector a)) #
Ixed (Vector a) #
Instance details Defined in Control.Lens.At Methods ix :: Index (Vector a) -> Traversal' (Vector a) (IxValue (Vector a)) #
Eq e => Ixed (e -> a) #
Instance details Defined in Control.Lens.At Methods ix :: Index (e -> a) -> Traversal' (e -> a) (IxValue (e -> a)) #
a ~ a2 => Ixed (a, a2) #
Instance details Defined in Control.Lens.At Methods ix :: Index (a, a2) -> Traversal' (a, a2) (IxValue (a, a2)) #
(IArray UArray e, Ix i) => Ixed (UArray i e) #	arr `!` i ≡ arr `^.` `ix` i arr `//` [(i,e)] ≡ `ix` i `.~` e `$` arr
Instance details Defined in Control.Lens.At Methods ix :: Index (UArray i e) -> Traversal' (UArray i e) (IxValue (UArray i e)) #
Ix i => Ixed (Array i e) #	arr `!` i ≡ arr `^.` `ix` i arr `//` [(i,e)] ≡ `ix` i `.~` e `$` arr
Instance details Defined in Control.Lens.At Methods ix :: Index (Array i e) -> Traversal' (Array i e) (IxValue (Array i e)) #
Ord k => Ixed (Map k a) #
Instance details Defined in Control.Lens.At Methods ix :: Index (Map k a) -> Traversal' (Map k a) (IxValue (Map k a)) #
(Eq k, Hashable k) => Ixed (HashMap k a) #
Instance details Defined in Control.Lens.At Methods ix :: Index (HashMap k a) -> Traversal' (HashMap k a) (IxValue (HashMap k a)) #
(a ~ a2, a ~ a3) => Ixed (a, a2, a3) #
Instance details Defined in Control.Lens.At Methods ix :: Index (a, a2, a3) -> Traversal' (a, a2, a3) (IxValue (a, a2, a3)) #
(a ~ a2, a ~ a3, a ~ a4) => Ixed (a, a2, a3, a4) #
Instance details Defined in Control.Lens.At Methods ix :: Index (a, a2, a3, a4) -> Traversal' (a, a2, a3, a4) (IxValue (a, a2, a3, a4)) #
(a ~ a2, a ~ a3, a ~ a4, a ~ a5) => Ixed (a, a2, a3, a4, a5) #
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)) #
(a ~ a2, a ~ a3, a ~ a4, a ~ a5, a ~ a6) => Ixed (a, a2, a3, a4, a5, a6) #
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)) #
(a ~ a2, a ~ a3, a ~ a4, a ~ a5, a ~ a6, a ~ a7) => Ixed (a, a2, a3, a4, a5, a6, a7) #
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)) #
(a ~ a2, a ~ a3, a ~ a4, a ~ a5, a ~ a6, a ~ a7, a ~ a8) => Ixed (a, a2, a3, a4, a5, a6, a7, a8) #
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)) #
(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) #
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)) #

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

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) #

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 #

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 #

>>> 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 #
Instance details Defined in Control.Lens.At Methods contains :: Index IntSet -> Lens' IntSet Bool #
Ord a => Contains (Set a) #
Instance details Defined in Control.Lens.At Methods contains :: Index (Set a) -> Lens' (Set a) Bool #
(Eq a, Hashable a) => Contains (HashSet a) #
Instance details Defined in Control.Lens.At Methods contains :: Index (HashSet a) -> Lens' (HashSet a) Bool #

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

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]