Set pop and shift

set.js

@@ -101,6 +101,22 @@ Set.prototype["delete"] = function (value) {
     return false;
 };
 
+Set.prototype.pop = function () {
+    if (this.length) {
+        var result = this.order.head.prev.value;
+        this["delete"](result);
+        return result;
+    }
+};
+
+Set.prototype.shift = function () {
+    if (this.length) {
+        var result = this.order.head.next.value;
+        this["delete"](result);
+        return result;
+    }
+};
+
 Set.prototype.one = function () {
     if (this.length > 0) {
         return this.store.one().value;

spec/set-spec.js

@@ -19,5 +19,14 @@ describe("Set", function () {
         return Set(values, Object.is);
     }, [{}, {}, {}, {}], true);
 
+    it("should pop and shift", function () {
+        var a = {i: 2};
+        var b = {i: 1};
+        var c = {i: 0};
+        var set = Set([a, b, c], Object.is);
+        expect(set.pop()).toBe(c);
+        expect(set.shift()).toBe(a);
+    });
+
 });