ceph/src/boost/libs/spirit/example/x3/complex_number.cpp

   1 /*=============================================================================
   2     Copyright (c) 2002-2015 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 complex number micro parser.
  10 //
  11 //  [ JDG May 10, 2002 ]    spirit1
  12 //  [ JDG May 9, 2007 ]     spirit2
  13 //  [ JDG May 12, 2015 ]    spirit X3
  14 //
  15 ///////////////////////////////////////////////////////////////////////////////
  16
  17 #include <boost/config/warning_disable.hpp>
  18 #include <boost/spirit/home/x3.hpp>
  19
  20 #include <iostream>
  21 #include <string>
  22 #include <complex>
  23
  24 ///////////////////////////////////////////////////////////////////////////////
  25 //  Our complex number parser/compiler
  26 ///////////////////////////////////////////////////////////////////////////////
  27 namespace client
  28 {
  29     template <typename Iterator>
  30     bool parse_complex(Iterator first, Iterator last, std::complex<double>& c)
  31     {
  32         using boost::spirit::x3::double_;
  33         using boost::spirit::x3::_attr;
  34         using boost::spirit::x3::phrase_parse;
  35         using boost::spirit::x3::ascii::space;
  36
  37         double rN = 0.0;
  38         double iN = 0.0;
  39         auto fr = [&](auto& ctx){ rN = _attr(ctx); };
  40         auto fi = [&](auto& ctx){ iN = _attr(ctx); };
  41
  42         bool r = phrase_parse(first, last,
  43
  44             //  Begin grammar
  45             (
  46                     '(' >> double_[fr]
  47                         >> -(',' >> double_[fi]) >> ')'
  48                 |   double_[fr]
  49             ),
  50             //  End grammar
  51
  52             space);
  53
  54         if (!r || first != last) // fail if we did not get a full match
  55             return false;
  56         c = std::complex<double>(rN, iN);
  57         return r;
  58     }
  59 }
  60
  61 ////////////////////////////////////////////////////////////////////////////
  62 //  Main program
  63 ////////////////////////////////////////////////////////////////////////////
  64 int
  65 main()
  66 {
  67     std::cout << "/////////////////////////////////////////////////////////\n\n";
  68     std::cout << "\t\tA complex number micro parser for Spirit...\n\n";
  69     std::cout << "/////////////////////////////////////////////////////////\n\n";
  70
  71     std::cout << "Give me a complex number of the form r or (r) or (r,i) \n";
  72     std::cout << "Type [q or Q] to quit\n\n";
  73
  74     std::string str;
  75     while (getline(std::cin, str))
  76     {
  77         if (str.empty() || str[0] == 'q' || str[0] == 'Q')
  78             break;
  79
  80         std::complex<double> c;
  81         if (client::parse_complex(str.begin(), str.end(), c))
  82         {
  83             std::cout << "-------------------------\n";
  84             std::cout << "Parsing succeeded\n";
  85             std::cout << "got: " << c << std::endl;
  86             std::cout << "\n-------------------------\n";
  87         }
  88         else
  89         {
  90             std::cout << "-------------------------\n";
  91             std::cout << "Parsing failed\n";
  92             std::cout << "-------------------------\n";
  93         }
  94     }
  95
  96     std::cout << "Bye... :-) \n\n";
  97     return 0;
  98 }