diff -r 6d109e3804ac -r 9a001a04b634 Twig-1.3.0/lib/Twig/NodeTraverser.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Twig-1.3.0/lib/Twig/NodeTraverser.php	Tue Oct 25 23:56:28 2011 +0200
@@ -0,0 +1,89 @@
+<?php
+
+/*
+ * This file is part of Twig.
+ *
+ * (c) 2009 Fabien Potencier
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+/**
+ * Twig_NodeTraverser is a node traverser.
+ *
+ * It visits all nodes and their children and call the given visitor for each.
+ *
+ * @package    twig
+ * @author     Fabien Potencier <fabien@symfony.com>
+ */
+class Twig_NodeTraverser
+{
+    protected $env;
+    protected $visitors;
+
+    /**
+     * Constructor.
+     *
+     * @param Twig_Environment $env      A Twig_Environment instance
+     * @param array            $visitors An array of Twig_NodeVisitorInterface instances
+     */
+    public function __construct(Twig_Environment $env, array $visitors = array())
+    {
+        $this->env = $env;
+        $this->visitors = array();
+        foreach ($visitors as $visitor) {
+            $this->addVisitor($visitor);
+        }
+    }
+
+    /**
+     * Adds a visitor.
+     *
+     * @param Twig_NodeVisitorInterface $visitor A Twig_NodeVisitorInterface instance
+     */
+    public function addVisitor(Twig_NodeVisitorInterface $visitor)
+    {
+        if (!isset($this->visitors[$visitor->getPriority()])) {
+            $this->visitors[$visitor->getPriority()] = array();
+        }
+
+        $this->visitors[$visitor->getPriority()][] = $visitor;
+    }
+
+    /**
+     * Traverses a node and calls the registered visitors.
+     *
+     * @param Twig_NodeInterface $node A Twig_NodeInterface instance
+     */
+    public function traverse(Twig_NodeInterface $node)
+    {
+        ksort($this->visitors);
+        foreach ($this->visitors as $visitors) {
+            foreach ($visitors as $visitor) {
+                $node = $this->traverseForVisitor($visitor, $node);
+            }
+        }
+
+        return $node;
+    }
+
+    protected function traverseForVisitor(Twig_NodeVisitorInterface $visitor, Twig_NodeInterface $node = null)
+    {
+        if (null === $node) {
+            return null;
+        }
+
+        $node = $visitor->enterNode($node, $this->env);
+
+        foreach ($node as $k => $n) {
+            if (false !== $n = $this->traverseForVisitor($visitor, $n)) {
+                $node->setNode($k, $n);
+            } else {
+                $node->removeNode($k);
+            }
+        }
+
+        return $visitor->leaveNode($node, $this->env);
+    }
+}