Extra #2 - takeWhile

Keep elements from the start of a list while they satisfy a condition.

Example

takeWhile isEven [2, 4, 6, 7, 8] == [2, 4, 6]

Unit Test

import Html exposing (text)
import List


takeWhile : (a -> Bool) -> List a -> List a
takeWhile predicate list =
    -- your implementation here
    []


main : Html.Html a
main =
    Html.text
        <| case test of
            0 ->
                "Your implementation passed all tests."

            1 ->
                "Your implementation failed one test."

            x ->
                "Your implementation failed " ++ (toString x) ++ " tests."


test : Int
test =
    List.length
        <| List.filter ((==) False)
          [ (takeWhile isOdd [ 1, 2, 1 ] == [ 1 ])
          , (takeWhile isEven [ 1, 2, 1 ] == [])
          , (takeWhile isEven [] == [])
          , (takeWhile isEven [ 2, 4, 100000, 1 ] == [ 2, 4, 100000 ])
          , (takeWhile ((>) 5) (List.range 1 10) == [ 1, 2, 3, 4 ])
          , (takeWhile ((>) 50) (List.range 1 10) == List.range 1 10)


isEven x =
    x % 2 == 0


isOdd x =
    x % 2 /= 0

Hints

1. Recurse!

Solutions

Solutions