// In header: <boost/xpressive/regex_actions.hpp>


struct str {
  // member classes/structs/unions
  template<typename Sig> 
  struct result {
  };
  template<typename This, typename Sub> 
  struct result<This(Sub)> {
    // types
    typedef remove_reference< Sub >::type::string_type type;
  };

  // public member functions
  template<typename Sub> Sub::string_type operator()(Sub const &) const;
};