elm/exercises/series/Series.example

module Series exposing (..)

import String
import List
import Result


slices : Int -> String -> Result String (List (List Int))
slices size input =
  if size < 1 then
    Err ("Invalid size: " ++ toString size)
  else
    String.split "" input
      |> List.map String.toInt
      |> combine
      |> Result.map (takeRuns size)


takeRuns : Int -> List Int -> List (List Int)
takeRuns size numbers =
  let
    candidate =
      List.take size numbers
  in
    if List.length candidate < size || size < 1 then
      []
    else
      candidate :: takeRuns size (List.drop 1 numbers)


combine : List (Result x a) -> Result x (List a)
combine =
  List.foldr (Result.map2 (::)) (Ok [])