Relude.List

Utility functions to work with lists and NonEmpty lists.

Documentation

module Relude.List.Reexport

Most of the Data.List types and function.

Note, that list partial functions (e.g. head) are not exported from Data.List. Instead relude provides safe functions that work with NonEmpty. You can find them in the Relude.List.NonEmpty module instead.

module Relude.List.NonEmpty

Reexports from Data.List.NonEmpty and additional safe functions to work with list type in terms of NonEmpty.

(!!?) :: [a] -> Int -> Maybe a infix 9

Safer version of !!, returns a Maybe.

Get element from list using index value starting from `0`.

>>> [] !!? 0
Nothing

>>> ["a", "b", "c"] !!? 3
Nothing

>>> [1, 2, 3] !!? (-1)
Nothing

>>> ["a", "b", "c"] !!? 2
Just "c"

Since: 0.6.0.0

maybeAt :: Int -> [a] -> Maybe a

!!? with its arguments flipped.

Get element from list using index value starting from `0`.

>>> maybeAt 0 []
Nothing

>>> maybeAt 3 ["a", "b", "c"]
Nothing

>>> maybeAt (-1) [1, 2, 3]
Nothing

>>> maybeAt 2 ["a", "b", "c"]
Just "c"

Since: 1.0.0.0

partitionWith :: (a -> Either b c) -> [a] -> ([b], [c])

Partitions a list based on the result of function which produces an Either value. List of all elements producing Left are extracted, in order, to the first element of the output tuple. Similarly, a list of all elements producing Right are extracted to the second element of output.

>>> :{
 divideEvenOrShow :: Int -> Either Int String
 divideEvenOrShow n
     | even n = Left $ n `div` 2
     | otherwise = Right $ "Odd: " <> show n
 :}

>>> partitionWith divideEvenOrShow [1 .. 6]
([1,2,3],["Odd: 1","Odd: 3","Odd: 5"])

Since: 1.0.0.0