-module(rps).

-export([beats/1]).

-export([result/2]).

-export([tournament/2]).

beats(rock)     -> scissors;
beats(paper)    -> rock;
beats(scissors) -> paper.

result(X, Y) ->
    case {beats(X), beats(Y)} of
        {Y, _} -> win;
        {_, X} -> lose;
        _      -> draw
    end.

points({X, Y}) ->
    case result(X, Y) of
        win  -> 1;
        draw -> 0;
        lose -> -1
    end.

tournament(L1, L2) ->
    lists:sum(lists:map(fun points/1, lists:zip(L1, L2))).