diff -r ef2d00e46897 -r c2992fd74dad lemon/traits.h
--- a/lemon/traits.h	Wed Feb 22 12:45:59 2006 +0000
+++ b/lemon/traits.h	Wed Feb 22 18:26:56 2006 +0000
@@ -209,6 +209,19 @@
     static const bool value = true;
   };
 
+  template <typename Graph, typename Enable = void>
+  struct UndirectedTagIndicator {
+    static const bool value = false;
+  };
+
+  template <typename Graph>
+  struct UndirectedTagIndicator<
+    Graph, 
+    typename enable_if<typename Graph::UndirectedTag, void>::type
+  > {
+    static const bool value = true;
+  };
+
 
 
 }