Collections.shuffle().

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@4441 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/as/com/threerings/util/Collections.as

@@ -0,0 +1,25 @@
+package com.threerings.util {
+
+import mx.collections.ListCollectionView;
+
+/**
+ * Various collections-related utility methods.
+ */
+public class Collections
+{
+    /**
+     * Randomly shuffle the elements in the specified list.
+     */
+    public static function shuffle (collection :ListCollectionView) :void
+    {
+        // starting from the end of the list, repeatedly swap the element
+        // in question with a random element previous to it up
+        // to and including itself
+        for (var ii :int  = collection.length - 1; ii > 0; ii--) {
+            var idx :int = int(Math.random() * (ii + 1))
+            var item :Object = collection.getItemAt(idx);
+            collection.setItemAt(collection.setItemAt(item, ii), idx);
+        }
+    }
+}
+}