Imported existing code

libraries/include/boost/graph/tree_traits.hpp

@@ -0,0 +1,43 @@
+//  (C) Copyright Jeremy Siek 1999.
+// Distributed under the Boost Software License, Version 1.0. (See
+// accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_TREE_STRUCTURE_HPP
+#define BOOST_TREE_STRUCTURE_HPP
+
+namespace boost {
+
+  template <class T>
+  struct tree_traits {
+    typedef typename T::node_descriptor node_descriptor;    
+    typedef typename T::children_iterator children_iterator;    
+  };
+
+
+  template <class Tree, class TreeVisitor>
+  void traverse_tree(typename tree_traits<Tree>::node_descriptor v,
+                     Tree& t, TreeVisitor visitor)
+  {
+    visitor.preorder(v, t);
+    typename tree_traits<Tree>::children_iterator i, end;
+    tie(i, end) = children(v, t);
+    if (i != end) {
+      traverse_tree(*i++, t, visitor);
+      visitor.inorder(v, t);
+      while (i != end)
+        traverse_tree(*i++, t, visitor);
+    } else
+      visitor.inorder(v, t);
+    visitor.postorder(v, t);
+  }
+
+  struct null_tree_visitor {
+    template <typename Node, typename Tree> void preorder(Node, Tree&) { }
+    template <typename Node, typename Tree> void inorder(Node, Tree&) { }
+    template <typename Node, typename Tree> void postorder(Node, Tree&) { }
+  };
+
+} /* namespace boost */
+
+#endif /* BOOST_TREE_STRUCTURE_HPP */