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