indexOf.elm

module Hello exposing (..)

import Html exposing (text)
import List exposing (take, drop, head)


indexOf : a -> List a -> Int
indexOf target list =
    let
        f target n list =
            case head (drop n list) of
                Just h ->
                    if h == target then
                        n
                    else
                        f target (n + 1) list

                Nothing ->
                    -1
    in
        f target 0 list


main =
    let
        i =
            indexOf "c" [ "a", "b", "c" ]
    in
        text (toString i)