diff -r 3351c85ffa02 -r 0274acee0e35 lemon/bits/iterable_graph_extender.h
--- a/lemon/bits/iterable_graph_extender.h	Tue Jun 07 16:11:23 2005 +0000
+++ b/lemon/bits/iterable_graph_extender.h	Tue Jun 07 16:12:14 2005 +0000
@@ -3,6 +3,7 @@
 #define LEMON_ITERABLE_GRAPH_EXTENDER_H
 
 #include <lemon/invalid.h>
+#include <lemon/utility.h>
 
 namespace lemon {
   
@@ -10,6 +11,13 @@
   class IterableGraphExtender : public _Base {
   public:
 
+    /// Indicates that the graph is undirected.
+
+    ///\todo Better name?
+    ///
+    ///\bug Should it be here?
+    typedef False UndirTag;
+
     typedef _Base Parent;
     typedef IterableGraphExtender<_Base> Graph;
 
@@ -170,6 +178,15 @@
   class IterableUndirGraphExtender : public IterableGraphExtender<_Base> {
   public:
 
+    /// Indicates that the graph is undirected.
+
+    ///\todo Better name?
+    ///
+    ///\bug Should it be here?
+    ///\bug Should be tested in the concept checker whether it is defined
+    ///correctly.
+    typedef True UndirTag;
+
     typedef IterableGraphExtender<_Base> Parent;
     typedef IterableUndirGraphExtender<_Base> Graph;
     typedef typename Parent::Node Node;