};

   };

   typedef GraphExtender<SmartGraphBase> ExtendedSmartGraphBase;

   typedef GraphExtender<SmartGraphBase> ExtendedSmartGraphBase;

   ///This is a simple and fast graph implementation.

   ///This is a simple and fast graph implementation.

   ///It is also quite memory efficient, but at the price

   ///It is also quite memory efficient, but at the price

   ///that <b> it does support only limited (only stack-like)

   ///that <b> it does support only limited (only stack-like)

   ///node and edge deletions</b>.

   ///node and edge deletions</b>.

   ///It conforms to 

   ///It conforms to 

       edges[n].target = u.id;

       edges[n].target = u.id;

       edges[n | 1].target = v.id;

       edges[n | 1].target = v.id;

       edges[n].next_out = nodes[v.id].first_out;

       edges[n].next_out = nodes[v.id].first_out;

       nodes[v.id].first_out = n;

       nodes[v.id].first_out = n;

       nodes[u.id].first_out = (n | 1);

       nodes[u.id].first_out = (n | 1);

       return UEdge(n / 2);

       return UEdge(n / 2);

     }

     }