// In header: <boost/log/expressions/attr.hpp>
template<typename T, typename FallbackPolicyT, typename TagT> 
class attribute_terminal {
public:
  // types
  typedef TagT                                  tag_type;         // Attribute tag type. 
  typedef value_extractor_type::value_type      value_type;       // Attribute value type. 
  typedef value_extractor_type::fallback_policy fallback_policy;  // Fallback policy type. 
  // member classes/structs/unions
  // Function result type.
  template<typename > 
  struct result {
  };
  template<typename ThisT, typename ContextT> 
  struct result<ThisT(ContextT)> {
    // types
    typedef remove_cv< typename remove_reference< typename phoenix::result_of::env< ContextT >::type >::type >::type                          env_type;               
    typedef env_type::args_type                                                                                                               args_type;              
    typedef unspecified                                                                                                                       cv_value_extractor_type;
    typedef boost::result_of< cv_value_extractor_type(attribute_name const &, typename fusion::result_of::at_c< args_type, 0 >::type) >::type type;                   
  };
  // construct/copy/destruct
  explicit attribute_terminal(attribute_name const &);
  template<typename U> attribute_terminal(attribute_name const &, U const &);
  attribute_terminal() = delete;
  // public member functions
  attribute_name get_name() const;
  fallback_policy const & get_fallback_policy() const;
  template<typename ContextT> 
    result< this_type(ContextT const &) >::type operator()(ContextT const &);
  template<typename ContextT> 
    result< const this_type(ContextT const &) >::type 
    operator()(ContextT const &) const;
};