1 files changed, 11 insertions, 0 deletions
diff --git a/src/utility.js b/src/utility.js
index 3d8ce86e..d5583ffb 100644
--- a/src/utility.js
+++ b/src/utility.js
@@ -202,3 +202,14 @@ function setSub(x, y) {
   return ret;
 }
 
+// Intersection of 2 sets. Faster if |xx| << |yy|
+function setIntersect(x, y) {
+  var ret = {};
+  for (xx in x) {
+    if (xx in y) {
+      ret[xx] = true;
+    }
+  }
+  return ret;
+}
+