1 files changed, 9 insertions, 1 deletions
diff --git a/src/utility.js b/src/utility.js
index b67e6c21..9cc8d3a3 100644
--- a/src/utility.js
+++ b/src/utility.js
@@ -298,12 +298,20 @@ function setIntersect(x, y) {
   var ret = {};
   for (xx in x) {
     if (xx in y) {
-      ret[xx] = true;
+      ret[xx] = 0;
     }
   }
   return ret;
 }
 
+function setUnion(x, y) {
+  var ret = set(keys(x));
+  for (yy in y) {
+    ret[yy] = 0;
+  }
+  return ret;
+}
+
 function invertArray(x) {
   var ret = {};
   for (var i = 0; i < x.length; i++) {