Problem 19

Rotate a list n places to the left (negative values will rotate to the right). Allow rotations greater than the list length.

Example

[rotate 3 (List.range 1 10), rotate 11 (List.range 1 10) ] == 
  [ [4, 5, 6, 7, 8, 9, 10, 1, 2, 3]
  , [2, 3, 4, 5, 6, 7, 8, 9, 10, 1]
  ]

Unit Test

import Html
import List


rotate : Int -> List a -> List a
rotate rot list =
    []


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)
            [ rotate 3 [ 1, 2, 5, 5, 2, 1 ] == [ 5, 2, 1, 1, 2, 5 ]
            , rotate 13 (List.range 1 10) == [ 4, 5, 6, 7, 8, 9, 10, 1, 2, 3 ]
            , rotate 1 (List.range 1 5) == [ 2, 3, 4, 5, 1 ]
            , rotate 0 (List.range 1 5) == [ 1, 2, 3, 4, 5 ]
            , rotate -1 (List.range 1 5) == [ 5, 1, 2, 3, 4 ]
            , rotate -6 (List.range 1 5) == [ 5, 1, 2, 3, 4 ]
            , rotate 3 (List.range 1 5) == [ 4, 5, 1, 2, 3 ]
            , rotate 1 [ "1", "2", "3", "4" ] == [ "2", "3", "4", "1" ]
            , rotate 1 [] == []
            ]

Hints

1. Take and ...

   Solutions

   Solutions