Data.List.Lens

Traversals for manipulating parts of a list.

Documentation

_head :: Simple Lens [a] a

A lens reading and writing to the head of a non-empty list

 ghci> [1,2,3]^._head
 1

_tail :: Simple Lens [a] [a]

A lens reading and writing to the tail of a non-empty list

 ghci> _tail <~ [3,4,5] $ [1,2]
 [1,3,4,5]

_last :: Simple Lens [a] a

A lens reading and writing to the last element of a non-empty list

_init :: Simple Lens [a] [a]

A lens reading and replacing all but the a last element of a non-empty list

interspersed :: a -> Getter [a] [a]

Obtain a version of the list with the supplied value interspersed.

 ghci> "abcde"^.interspersed ','
 "a,b,c,d,e"

 xs^.interspersed a = intersperse a xs

intercalated :: [a] -> Getter [[a]] [a]

Obtain a version of the list with the supplied value intercalated

traverseHead :: SimpleTraversal [a] a

The traversal for reading and writing to the head of a list

 traverseHead :: Applicative f => (a -> f a) -> [a] -> f [a]

traverseTail :: SimpleTraversal [a] a

Traversal for editing the tail of a list.

 traverseTail :: Applicative f => (a -> f a) -> [a] -> f [a]

traverseInit :: SimpleTraversal [a] a

Traverse all but the last element of a list

 traverseInit :: Applicative f => (a -> f a) -> [a] -> f [a]

traverseLast :: SimpleTraversal [a] a

Traverse the last element in a list.

 traverseLast :: Applicative f => (a -> f a) -> [a] -> f [a]