rects intersection

rect.erl

%
% Rect library - work with rects
%
-module(rect).

-export([intersect/2, normalize/1]).


intersect(R1, R2) ->
    {{X1, Y1}, {X2, Y2}} = R1,
    {{OX1, OY1}, {OX2, OY2}} = R2,
    intersect_proections({X1, X2}, {OX1, OX2}) orelse intersect_proections({Y1, Y2}, {OY1, OY2}).

intersect_proections({X1, X2}, {OX1, OX2}) ->
    case lists:sort([{X1, recta}, {X2, recta}, {OX1, rectb}, {OX2, rectb}]) of
        [{_, recta}, {_, recta}|_] -> false;
        [{_, rectb}, {_, rectb}|_] -> false;
        _ -> true
    end.

normalize({{X1, Y1}, {X2, Y2}}) ->
    {
        {min(X1, X2), min(Y1, Y2)},
        {max(X1, X2), max(Y1, Y2)}
    }.

%% ===================================================================
%% testing
%% ===================================================================

-ifdef(TEST).
-include_lib("eunit/include/eunit.hrl").

-define(R1, {{1, 1}, {3, 3}}).
-define(R2, {{2, 2}, {3, 3}}).
-define(R3, {{2, 5}, {3, 3}}).
-define(R3n, {{2, 3}, {3, 5}}).

rects_test() ->
    ?assertEqual(normalize(?R3), ?R3n),
    ?assertEqual(intersect(?R1, ?R2), true).


-endif.