Safe Haskell	Safe
Language	Haskell2010

Optic.Prism.Snoc

Contents

Snoc

Synopsis

class Snoc s t a b | s -> a, t -> b, s b -> t, t a -> s where
(|>) :: Snoc s s a a => s -> a -> s
snoc :: Snoc s s a a => s -> a -> s
unsnoc :: Snoc s s a a => s -> Maybe (s, a)
_init :: Snoc s s a a => Traversal' s s
_last :: Snoc s s a a => Traversal' s a
pattern (:>) :: forall a b. Snoc a a b b => a -> b -> a

Snoc

class 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.

Minimal complete definition

_Snoc

Methods

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

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

Instances

Snoc ByteString ByteString Word8 Word8
Instance details Defined in Control.Lens.Cons Methods _Snoc :: Prism ByteString ByteString (ByteString, Word8) (ByteString, Word8) #
Snoc ByteString ByteString Word8 Word8
Instance details Defined in Control.Lens.Cons Methods _Snoc :: Prism ByteString ByteString (ByteString, Word8) (ByteString, Word8) #
Snoc Text Text Char Char
Instance details Defined in Control.Lens.Cons Methods _Snoc :: Prism Text Text (Text, Char) (Text, Char) #
Snoc Text Text Char Char
Instance details Defined in Control.Lens.Cons Methods _Snoc :: Prism Text Text (Text, Char) (Text, Char) #
Snoc [a] [b] a b
Instance details Defined in Control.Lens.Cons Methods _Snoc :: Prism [a] [b] ([a], a) ([b], b) #
Snoc (ZipList a) (ZipList b) a b
Instance details Defined in Control.Lens.Cons Methods _Snoc :: Prism (ZipList a) (ZipList b) (ZipList a, a) (ZipList b, b) #
Snoc (Seq a) (Seq b) a b
Instance details Defined in Control.Lens.Cons Methods _Snoc :: Prism (Seq a) (Seq b) (Seq a, a) (Seq b, b) #
(Prim a, Prim b) => Snoc (Vector a) (Vector b) a b
Instance details Defined in Control.Lens.Cons Methods _Snoc :: Prism (Vector a) (Vector b) (Vector a, a) (Vector b, b) #
(Storable a, Storable b) => Snoc (Vector a) (Vector b) a b
Instance details Defined in Control.Lens.Cons Methods _Snoc :: Prism (Vector a) (Vector b) (Vector a, a) (Vector b, b) #
(Unbox a, Unbox b) => Snoc (Vector a) (Vector b) a b
Instance details Defined in Control.Lens.Cons Methods _Snoc :: Prism (Vector a) (Vector b) (Vector a, a) (Vector b, b) #
Snoc (Vector a) (Vector b) a b
Instance details Defined in Control.Lens.Cons Methods _Snoc :: Prism (Vector a) (Vector b) (Vector a, a) (Vector b, b) #

(|>) :: Snoc s s a a => s -> a -> s infixl 5 #

snoc an element onto the end of a container.

This is an infix alias for snoc.

>>> Seq.fromList [] |> a
fromList [a]

>>> Seq.fromList [b, c] |> a
fromList [b,c,a]

>>> LazyT.pack "hello" |> '!'
"hello!"

snoc :: Snoc s s a a => s -> a -> s infixl 5 #

snoc an element onto the end of a container.

>>> snoc (Seq.fromList []) a
fromList [a]

>>> snoc (Seq.fromList [b, c]) a
fromList [b,c,a]

>>> snoc (LazyT.pack "hello") '!'
"hello!"

unsnoc :: 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.

>>> unsnoc (LazyT.pack "hello!")
Just ("hello",'!')

>>> unsnoc (LazyT.pack "")
Nothing

>>> unsnoc (Seq.fromList [b,c,a])
Just (fromList [b,c],a)

>>> unsnoc (Seq.fromList [])
Nothing

_init :: Snoc s s a a => Traversal' s s #

A Traversal reading and replacing all but the a last element of a non-empty container.

>>> [a,b,c,d]^?_init
Just [a,b,c]

>>> []^?_init
Nothing

>>> [a,b] & _init .~ [c,d,e]
[c,d,e,b]

>>> [] & _init .~ [a,b]
[]

>>> [a,b,c,d] & _init.traverse %~ f
[f a,f b,f c,d]

>>> [1,2,3]^?_init
Just [1,2]

>>> [1,2,3,4]^?!_init
[1,2,3]

>>> "hello"^._init
"hell"

>>> ""^._init
""

_init :: Traversal' [a] [a]
_init :: Traversal' (Seq a) (Seq a)
_init :: Traversal' (Vector a) (Vector a)

_last :: Snoc s s a a => Traversal' s a #

A Traversal reading and writing to the last element of a non-empty container.

>>> [a,b,c]^?!_last
c

>>> []^?_last
Nothing

>>> [a,b,c] & _last %~ f
[a,b,f c]

>>> [1,2]^?_last
Just 2

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

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

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

This Traversal is not limited to lists, however. We can also work with other containers, such as a Vector.

>>> Vector.fromList "abcde" ^? _last
Just 'e'

>>> Vector.empty ^? _last
Nothing

>>> (Vector.fromList "abcde" & _last .~ 'Q') == Vector.fromList "abcdQ"
True

_last :: Traversal' [a] a
_last :: Traversal' (Seq a) a
_last :: Traversal' (Vector a) a

pattern (:>) :: forall a b. Snoc a a b b => a -> b -> a infixl 5 #