template<typename Signature, typename Combiner, typename Group, 
         typename GroupCompare> 
class filter<Signature, unfused, Combiner, Group, GroupCompare> {
public:
  // types
  typedef Signature                                                 signature_type;
  typedef boost::signal< Signature, 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() ;
};