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

  // construct/copy/destruct
  filter& operator=(const filter &);

  // public member functions
   filter(const filter &) ;
   filter() ;
  signal_type & default_signal() const;
  void disconnect_all_slots() ;
};