X-Git-Url: https://git.enpas.org/?a=blobdiff_plain;f=util%2Fset.lua;h=ee154ece11e1f5977be607735fa197acf10de4e4;hb=4643eae0bf41b461c9337bfb66f9ac80f7e84f11;hp=892f1c9d3f70e14bc75a3d36df9ebdcd98531078;hpb=e5d38fe21c831c19260459efa36c33e793c57cb6;p=prosody.git

diff --git a/util/set.lua b/util/set.lua
index 892f1c9d..ee154ece 100644
--- a/util/set.lua
+++ b/util/set.lua
@@ -1,3 +1,11 @@
+-- Prosody IM
+-- Copyright (C) 2008-2010 Matthew Wild
+-- Copyright (C) 2008-2010 Waqas Hussain
+-- 
+-- This project is MIT/X11 licensed. Please see the
+-- COPYING file in the source package for more information.
+--
+
 local ipairs, pairs, setmetatable, next, tostring = 
       ipairs, pairs, setmetatable, next, tostring;
 local t_concat = table.concat;
@@ -91,6 +99,10 @@ function new(list)
 		end
 	end
 	
+	function set:empty()
+		return not next(items);
+	end
+	
 	if list then
 		set:add_list(list);
 	end
@@ -137,4 +149,8 @@ function intersection(set1, set2)
 	return set;
 end
 
+function xor(set1, set2)
+	return union(set1, set2) - intersection(set1, set2);
+end
+
 return _M;