Moduleoptics-core-0.4.1.1Haskell2010

Optics.Cons.Core

This module defines the Cons and Snoc classes, which provide Prisms for the leftmost and rightmost elements of a container, respectively.

Note that orphan instances for these classes are defined in the Optics.Cons module from optics-extra, so if you are not simply depending on optics you may wish to import that module instead.

2 classes
10 values

Packageoptics-core-0.4.1.1
Exports14
LanguageHaskell2010
LicenceBSD-3-Clause
SourceCore.hs

Cons

7 declarations

classclass Cons s t a b | s -> a, t -> b, s b -> t, t a -> s where

This class provides a way to attach or detach elements on the left side of a structure in a flexible manner.

Methods

_Cons :: Prism s t (a, s) (b, t)

_Cons :: Prism [a] [b] (a, [a]) (b, [b])
_Cons :: Prism (Seq a) (Seq b) (a, Seq a) (b, Seq b)
_Cons :: Prism (Vector a) (Vector b) (a, Vector a) (b, Vector b)
_Cons :: Prism' String (Char, String)
_Cons :: Prism' Text (Char, Text)
_Cons :: Prism' ByteString (Word8, ByteString)

Instances3Cons

Cons (Seq a) (Seq b) a bDefined in optics-core-0.4.1.1 · Optics.Cons.Core
Cons (ZipList a) (ZipList b) a bDefined in optics-core-0.4.1.1 · Optics.Cons.Core
Cons [a] [b] a bDefined in optics-core-0.4.1.1 · Optics.Cons.Core

value(<|) :: Cons s s a a => a -> s -> s

cons an element onto a container.

This is an infix alias for cons.

Example1 expression

>>> 1 <| [][1]

Example1 expression

>>> 'a' <| "bc""abc"

Example1 expression

>>> 1 <| [][1]

Example1 expression

>>> 1 <| [2, 3][1,2,3]

valuecons :: Cons s s a a => a -> s -> s

cons an element onto a container.

Example1 expression

>>> cons 'a' """a"

Example1 expression

>>> cons 'a' "bc""abc"

valueuncons :: Cons s s a a => s -> Maybe (a, s)

Attempt to extract the left-most element from a container, and a version of the container without that element.

Example1 expression

>>> uncons []Nothing

Example1 expression

>>> uncons [1, 2, 3]Just (1,[2,3])

value_head :: Cons s s a a => AffineTraversal' s a

An AffineTraversal reading and writing to the head of a non-empty container.

Example1 expression

>>> "abc" ^? _headJust 'a'

Example1 expression

>>> "abc" & _head .~ 'd'"dbc"

Example1 expression

>>> [1,2,3] & _head %~ (*10)[10,2,3]

Example1 expression

>>> [] & _head %~ absurd[]

Example1 expression

>>> [1,2,3] ^? _headJust 1

Example1 expression

>>> [] ^? _headNothing

Example1 expression

>>> [1,2] ^? _headJust 1

Example1 expression

>>> [] & _head .~ 1[]

Example1 expression

>>> [0] & _head .~ 2[2]

Example1 expression

>>> [0,1] & _head .~ 2[2,1]

value_tail :: Cons s s a a => AffineTraversal' s s

An AffineTraversal reading and writing to the tail of a non-empty container.

Example1 expression

>>> "ab" & _tail .~ "cde""acde"

Example1 expression

>>> [] & _tail .~ [1,2][]

Example1 expression

>>> [1,2,3,4,5] & _tail % traversed %~ (*10)[1,20,30,40,50]

Example1 expression

>>> [1,2] & _tail .~ [3,4,5][1,3,4,5]

Example1 expression

>>> [] & _tail .~ [1,2][]

Example1 expression

>>> "abc" ^? _tailJust "bc"

Example1 expression

>>> "hello" ^? _tailJust "ello"

Example1 expression

>>> "" ^? _tailNothing

patternpattern (:<) :: Cons s s a a => a -> s -> s

Pattern synonym for matching on the leftmost element of a structure.

Example1 expression

>>> case ['a','b','c'] of (x :< _) -> x'a'

Snoc

7 declarations

classclass Snoc s t a b | s -> a, t -> b, s b -> t, t a -> s where

This class provides a way to attach or detach elements on the right side of a structure in a flexible manner.

Methods

_Snoc :: Prism s t (s, a) (t, b)

Instances3Snoc

Snoc (Seq a) (Seq b) a bDefined in optics-core-0.4.1.1 · Optics.Cons.Core
Snoc (ZipList a) (ZipList b) a bDefined in optics-core-0.4.1.1 · Optics.Cons.Core
Snoc [a] [b] a bDefined in optics-core-0.4.1.1 · Optics.Cons.Core

value(|>) :: Snoc s s a a => s -> a -> s

snoc an element onto the end of a container.

This is an infix alias for snoc.

Example1 expression

>>> "" |> 'a'"a"

Example1 expression

>>> "bc" |> 'a'"bca"

valuesnoc :: Snoc s s a a => s -> a -> s

snoc an element onto the end of a container.

Example1 expression

>>> snoc "hello" '!'"hello!"

valueunsnoc :: Snoc s s a a => s -> Maybe (s, a)

Attempt to extract the right-most element from a container, and a version of the container without that element.

Example1 expression

>>> unsnoc "hello!"Just ("hello",'!')

Example1 expression

>>> unsnoc ""Nothing

value_init :: Snoc s s a a => AffineTraversal' s s

An AffineTraversal reading and replacing all but the a last element of a non-empty container.

Example1 expression

>>> "abcd" ^? _initJust "abc"

Example1 expression

>>> "" ^? _initNothing

Example1 expression

>>> "ab" & _init .~ "cde""cdeb"

Example1 expression

>>> [] & _init .~ [1,2][]

Example1 expression

>>> [1,2,3,4] & _init % traversed %~ (*10)[10,20,30,4]

Example1 expression

>>> [1,2,3] ^? _initJust [1,2]

Example1 expression

>>> "hello" ^? _initJust "hell"

Example1 expression

>>> [] ^? _initNothing

value_last :: Snoc s s a a => AffineTraversal' s a

An AffineTraversal reading and writing to the last element of a non-empty container.

Example1 expression

>>> "abc" ^? _lastJust 'c'

Example1 expression

>>> "" ^? _lastNothing

Example1 expression

>>> [1,2,3] & _last %~ (+1)[1,2,4]

Example1 expression

>>> [1,2] ^? _lastJust 2

Example1 expression

>>> [] & _last .~ 1[]

Example1 expression

>>> [0] & _last .~ 2[2]

Example1 expression

>>> [0,1] & _last .~ 2[0,2]

patternpattern (:>) :: Snoc s s a a => s -> a -> s

Pattern synonym for matching on the rightmost element of a structure.

Example1 expression

>>> case ['a','b','c'] of (_ :> x) -> x'c'