// In header: <boost/log/expressions/predicates/channel_severity_filter.hpp>
template<typename ChannelT, typename SeverityT, 
         typename ChannelFallbackT = fallback_to_none, 
         typename SeverityFallbackT = fallback_to_none, 
         typename ChannelOrderT = less, 
         typename SeverityCompareT = greater_equal, 
         typename AllocatorT = std::allocator< void > > 
class channel_severity_filter_terminal {
public:
  // types
  typedef bool              result_type;               // Function result type. 
  typedef ChannelT          channel_value_type;        // Channel attribute value type. 
  typedef ChannelFallbackT  channel_fallback_policy;   // Channel fallback policy. 
  typedef SeverityT         severity_value_type;       // Severity level attribute value type. 
  typedef SeverityFallbackT severity_fallback_policy;  // Severity level fallback policy. 
  // member classes/structs/unions
  // Channel visitor.
  template<typename ArgT> 
  struct channel_visitor {
    // types
    typedef void result_type;
    // construct/copy/destruct
    channel_visitor(channel_severity_filter_terminal const &, ArgT, bool &);
    // public member functions
    result_type operator()(channel_value_type const &) const;
  };
  // Severity level visitor.
  struct severity_visitor {
    // types
    typedef void result_type;
    // construct/copy/destruct
    severity_visitor(channel_severity_filter_terminal const &, 
                     severity_value_type const &, bool &);
    // public member functions
    result_type operator()(severity_value_type const &) const;
  };
  // construct/copy/destruct
  channel_severity_filter_terminal(attribute_name const &, 
                                   attribute_name const &, 
                                   channel_fallback_policy const & = channel_fallback_policy(), 
                                   severity_fallback_policy const & = severity_fallback_policy(), 
                                   ChannelOrderT const & = ChannelOrderT(), 
                                   SeverityCompareT const & = SeverityCompareT());
  // public member functions
  void add(channel_value_type const &, severity_value_type const &);
  void set_default(bool);
  template<typename ContextT> result_type operator()(ContextT const &) const;
  // private member functions
  template<typename ArgT> 
    void visit_channel(channel_value_type const &, ArgT const &, bool &) const;
  void visit_severity(severity_value_type const &, 
                      severity_value_type const &, bool &) const;
};