ceph/src/boost/libs/spirit/example/qi/compiler_tutorial/calc3.cpp

   1 /*=============================================================================
   2     Copyright (c) 2001-2011 Joel de Guzman
   3
   4     Distributed under the Boost Software License, Version 1.0. (See accompanying
   5     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   6 =============================================================================*/
   7 ///////////////////////////////////////////////////////////////////////////////
   8 //
   9 //  A calculator example demonstrating the grammar and semantic actions
  10 //  using phoenix to do the actual expression evaluation. The parser is
  11 //  essentially an "interpreter" that evaluates expressions on the fly.
  12 //
  13 //  [ JDG June 29, 2002 ]   spirit1
  14 //  [ JDG March 5, 2007 ]   spirit2
  15 //
  16 ///////////////////////////////////////////////////////////////////////////////
  17
  18 // Spirit v2.5 allows you to suppress automatic generation
  19 // of predefined terminals to speed up complation. With
  20 // BOOST_SPIRIT_NO_PREDEFINED_TERMINALS defined, you are
  21 // responsible in creating instances of the terminals that
  22 // you need (e.g. see qi::uint_type uint_ below).
  23 #define BOOST_SPIRIT_NO_PREDEFINED_TERMINALS
  24
  25 #include <boost/spirit/include/qi.hpp>
  26 #include <boost/phoenix/operator.hpp>
  27
  28 #include <iostream>
  29 #include <string>
  30
  31 namespace client
  32 {
  33     namespace qi = boost::spirit::qi;
  34     namespace ascii = boost::spirit::ascii;
  35
  36     ///////////////////////////////////////////////////////////////////////////
  37     //  Our calculator grammar
  38     ///////////////////////////////////////////////////////////////////////////
  39     template <typename Iterator>
  40     struct calculator : qi::grammar<Iterator, int(), ascii::space_type>
  41     {
  42         calculator() : calculator::base_type(expression)
  43         {
  44             qi::_val_type _val;
  45             qi::_1_type _1;
  46             qi::uint_type uint_;
  47
  48             expression =
  49                 term                            [_val = _1]
  50                 >> *(   ('+' >> term            [_val += _1])
  51                     |   ('-' >> term            [_val -= _1])
  52                     )
  53                 ;
  54
  55             term =
  56                 factor                          [_val = _1]
  57                 >> *(   ('*' >> factor          [_val *= _1])
  58                     |   ('/' >> factor          [_val /= _1])
  59                     )
  60                 ;
  61
  62             factor =
  63                 uint_                           [_val = _1]
  64                 |   '(' >> expression           [_val = _1] >> ')'
  65                 |   ('-' >> factor              [_val = -_1])
  66                 |   ('+' >> factor              [_val = _1])
  67                 ;
  68         }
  69
  70         qi::rule<Iterator, int(), ascii::space_type> expression, term, factor;
  71     };
  72 }
  73
  74 ///////////////////////////////////////////////////////////////////////////////
  75 //  Main program
  76 ///////////////////////////////////////////////////////////////////////////////
  77 int
  78 main()
  79 {
  80     std::cout << "/////////////////////////////////////////////////////////\n\n";
  81     std::cout << "Expression parser...\n\n";
  82     std::cout << "/////////////////////////////////////////////////////////\n\n";
  83     std::cout << "Type an expression...or [q or Q] to quit\n\n";
  84
  85     typedef std::string::const_iterator iterator_type;
  86     typedef client::calculator<iterator_type> calculator;
  87
  88     boost::spirit::ascii::space_type space; // Our skipper
  89     calculator calc; // Our grammar
  90
  91     std::string str;
  92     int result;
  93     while (std::getline(std::cin, str))
  94     {
  95         if (str.empty() || str[0] == 'q' || str[0] == 'Q')
  96             break;
  97
  98         std::string::const_iterator iter = str.begin();
  99         std::string::const_iterator end = str.end();
 100         bool r = phrase_parse(iter, end, calc, space, result);
 101
 102         if (r && iter == end)
 103         {
 104             std::cout << "-------------------------\n";
 105             std::cout << "Parsing succeeded\n";
 106             std::cout << "result = " << result << std::endl;
 107             std::cout << "-------------------------\n";
 108         }
 109         else
 110         {
 111             std::string rest(iter, end);
 112             std::cout << "-------------------------\n";
 113             std::cout << "Parsing failed\n";
 114             std::cout << "stopped at: \" " << rest << "\"\n";
 115             std::cout << "-------------------------\n";
 116         }
 117     }
 118
 119     std::cout << "Bye... :-) \n\n";
 120     return 0;
 121 }
 122
 123