elm/exercises/sublist/Sublist.example

module Sublist exposing (..)


version : Int
version =
  2


type ListComparison
  = Equal
  | Superlist
  | Sublist
  | Unequal


sublist : List a -> List a -> ListComparison
sublist alist blist =
  if alist == blist then
    Equal
  else if inList alist blist then
    Superlist
  else if inList blist alist then
    Sublist
  else
    Unequal


inList : List a -> List a -> Bool
inList alist blist =
  let
    getLastInList sublist =
      Maybe.withDefault [] (List.tail sublist)
  in
    if (List.length alist) < (List.length blist) then
      False
    else if (List.take (List.length blist) alist) == blist then
      True
    else
      inList (getLastInList alist) blist