text: /*=============================================================================
      Copyright (c) 2001-2010 Hartmut Kaiser
      Copyright (c) 2001-2010 Joel de Guzman
  
      Distributed under the Boost Software License, Version 1.0. (See accompanying
      file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  =============================================================================*/
  
  // This example is not meant to be a sophisticated date parser. It's sole 
  // purpose is to demonstrate the intrinsic attribute transformation 
  // capabilities of a rule. 
  // 
  // Note how the rule exposes a fusion sequence, but gets passed an instance of
  // a boost::gregorian::date as the attribute. In order to make these types 
  // compatible for the rule we define a specialization of the customization 
  // point called 'transform_attribute'.
  
  #include <boost/config/warning_disable.hpp>
  #include <boost/spirit/include/qi.hpp>
  #include <boost/fusion/include/vector.hpp>
  #include <boost/date_time.hpp>
  
  // define custom transformation
  namespace boost { namespace spirit { namespace traits
  {
      // This specialization of the customization point transform_attribute 
      // allows to pass a boost::gregorian::date to a rule which is expecting
      // a fusion sequence consisting out of three integers as its attribute.
      template<>
      struct transform_attribute<
          boost::gregorian::date, fusion::vector<int, int, int>, qi::domain>
      {
          typedef fusion::vector<int, int, int> date_parts;
  
          // The embedded typedef 'type' exposes the attribute as it will be 
          // passed to the right hand side of the rule. 
          typedef date_parts type;
  
          // The function pre() is called for down-stream conversion of the
          // attribute supplied to the rule to the attribute expected by the
          // right hand side.
          // The supplied attribute might have been pre-initialized by parsers
          // (i.e. semantic actions) higher up the parser hierarchy (in the 
          // grammar), in which case we would need to properly initialize the 
          // returned value from the argument. In this example this is not
          // required, so we just create a new instance of a date_parts.
          static date_parts pre(boost::gregorian::date) 
          { 
              return date_parts(); 
          }
  
          // The function post() is called for up-stream conversion of the 
          // results returned from parsing the right hand side of the rule.
          // We need to initialize the attribute supplied to the rule (referenced 
          // by the first argument) with the values taken from the parsing 
          // results (referenced by the second argument).
          static void post(boost::gregorian::date& d, date_parts const& v)
          {
              d = boost::gregorian::date(fusion::at_c<0>(v), fusion::at_c<1>(v)
                , fusion::at_c<2>(v));
          }
  
          // The function fail() is called whenever the parsing of the right hand
          // side of the rule fails. We don't need to do anything here.
          static void fail(boost::gregorian::date&) {}
      };
  }}}
  
  ///////////////////////////////////////////////////////////////////////////////
  namespace client
  {
      namespace qi = boost::spirit::qi;
  
      template <typename Iterator>
      bool parse_date(Iterator& first, Iterator last, boost::gregorian::date& d)
      {
          typedef boost::fusion::vector<int, int, int> date_parts;
          qi::rule<Iterator, date_parts(), qi::space_type> date =
              qi::int_ >> '-' >> qi::int_ >> '-' >> qi::int_;
  
          return phrase_parse(first, last, date, qi::space, d);
      }
  }
  
  ///////////////////////////////////////////////////////////////////////////////
  int main()
  {
      std::cout << "/////////////////////////////////////////////////////////\n\n";
      std::cout << "\t\tA date parser for Spirit...\n\n";
      std::cout << "/////////////////////////////////////////////////////////\n\n";
  
      std::cout << "Give me a date of the form : year-month-day\n";
      std::cout << "Type [q or Q] to quit\n\n";
  
      std::string str;
      while (getline(std::cin, str))
      {
          if (str.empty() || str[0] == 'q' || str[0] == 'Q')
              break;
  
          boost::gregorian::date d;
          std::string::const_iterator iter = str.begin();
          std::string::const_iterator end = str.end();
          bool r = client::parse_date(iter, end, d);
  
          if (r && iter == end)
          {
              std::cout << "-------------------------\n";
              std::cout << "Parsing succeeded\n";
              std::cout << "got: " << d << std::endl;
              std::cout << "\n-------------------------\n";
          }
          else
          {
              std::cout << "-------------------------\n";
              std::cout << "Parsing failed\n";
              std::cout << "-------------------------\n";
          }
      }
  
      std::cout << "Bye... :-) \n\n";
      return 0;
  }
  
  
  