From 2277a5b2388929e9448952816baa45655bcc516a Mon Sep 17 00:00:00 2001
From: Kris Maglione <maglione.k@gmail.com>
Date: Sat, 22 Feb 2014 10:20:09 -0800
Subject: [PATCH] Add difference, intersection, and union methods to RealSet.

---
 common/modules/base.jsm | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/common/modules/base.jsm b/common/modules/base.jsm
index 25376a26..a45a4070 100644
--- a/common/modules/base.jsm
+++ b/common/modules/base.jsm
@@ -395,6 +395,21 @@ RealSet.prototype.add = function RealSet_add(val) {
     return res;
 };
 
+RealSet.prototype.difference = function RealSet_difference(set) {
+    return RealSet(i for (i of this) if (!set.has(i)));
+};
+
+RealSet.prototype.intersection = function RealSet_intersection(set) {
+    return RealSet(i for (i of this) if (set.has(i)));
+};
+
+RealSet.prototype.union = function RealSet_union(set) {
+    let res = RealSet(this);
+    for (let item of set)
+        res.add(item);
+    return res;
+};
+
 /**
  * Utility for managing sets of strings. Given an array, returns an
  * object with one key for each value thereof.