Round Robin Elm

RoundRobin.Elm

module RoundRobin where

import Graphics.Element exposing (show)
import Set
import Array

type alias Team = String
type alias TeamMatch = (Team, Team)

removeRedundentMatches : List TeamMatch -> List TeamMatch
removeRedundentMatches allMatches =
  let
    reverseMatch match = (snd match, fst match)

    isReverseInList match matches =
      List.member (reverseMatch match) matches

    isSameTeamMatch (teamA, teamB) =
      teamA == teamB

    isValidMatch match matches =
      not (isSameTeamMatch match) && not (isReverseInList match matches)

    filterReverseMatches match matches =
      if isValidMatch match matches then
        -- this line can potentially be improved
        Array.toList <| Array.push match (Array.fromList matches)
      else
        matches
  in
    List.foldr filterReverseMatches [] allMatches

mapMatch : List Team -> Team -> List TeamMatch
mapMatch teamList team =
  List.map ((,) team) teamList

matches : List Team -> List TeamMatch
matches teamList =
  teamList
    |> List.map (mapMatch teamList)
    |> List.concat
    |> removeRedundentMatches

main =
  show (toString <| matches ["A", "B", "C", "D"])