// -*- c++ -*-

 #ifndef LEMON_CLEARABLE_GRAPH_EXTENDER_H

 #define LEMON_CLEARABLE_GRAPH_EXTENDER_H

 #include <lemon/invalid.h>

 namespace lemon {

   template <typename _Base> 

   class ClearableGraphExtender : public _Base {

   public:

     typedef ClearableGraphExtender Graph;

     typedef _Base Parent;

     typedef typename Parent::Node Node;

     typedef typename Parent::Edge Edge;

     void clear() {

       Parent::getObserverRegistry(Node()).clear();

       Parent::getObserverRegistry(Edge()).clear();

       Parent::clear();

     }

   };

 }

 #endif