template<typename Signature, typename Combiner, typename Group, 
         typename GroupCompare> 
class filter<Signature, combined, Combiner, Group, GroupCompare> : public boost::signals::filter< Signature, unfused, Combiner, Group, GroupCompare >
{
public:
  // types
  typedef base_type::signature_type                                    signature_type;      
  typedef base_type::signal_type                                       signal_type;         
  typedef boost::function_types::parameter_types< Signature >::type    parameter_types;     
  typedef boost::fusion::result_of::as_vector< parameter_types >::type parameter_vector;    
  typedef signal_type::result_type                                     fused_signature_type;

  // public member functions
   filter() ;
};