ceph/src/boost/libs/spirit/example/x3/sum.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 parser for summing a comma-separated list of numbers using phoenix.
  10 //
  11 //  [ JDG June 28, 2002 ]   spirit1
  12 //  [ JDG March 24, 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 #include <iostream>
  20 #include <string>
  21
  22 namespace client
  23 {
  24     namespace x3 = boost::spirit::x3;
  25     namespace ascii = boost::spirit::x3::ascii;
  26
  27     using x3::double_;
  28     using ascii::space;
  29     using x3::_attr;
  30
  31     ///////////////////////////////////////////////////////////////////////////
  32     //  Our adder
  33     ///////////////////////////////////////////////////////////////////////////
  34
  35     template <typename Iterator>
  36     bool adder(Iterator first, Iterator last, double& n)
  37     {
  38         auto assign = [&](auto& ctx){ n = _attr(ctx); };
  39         auto add = [&](auto& ctx){ n += _attr(ctx); };
  40
  41         bool r = x3::phrase_parse(first, last,
  42
  43             //  Begin grammar
  44             (
  45                 double_[assign] >> *(',' >> double_[add])
  46             )
  47             ,
  48             //  End grammar
  49
  50             space);
  51
  52         if (first != last) // fail if we did not get a full match
  53             return false;
  54         return r;
  55     }
  56 }
  57
  58 ////////////////////////////////////////////////////////////////////////////
  59 //  Main program
  60 ////////////////////////////////////////////////////////////////////////////
  61 int
  62 main()
  63 {
  64     std::cout << "/////////////////////////////////////////////////////////\n\n";
  65     std::cout << "\t\tA parser for summing a list of numbers...\n\n";
  66     std::cout << "/////////////////////////////////////////////////////////\n\n";
  67
  68     std::cout << "Give me a comma separated list of numbers.\n";
  69     std::cout << "The numbers are added using Phoenix.\n";
  70     std::cout << "Type [q or Q] to quit\n\n";
  71
  72     std::string str;
  73     while (getline(std::cin, str))
  74     {
  75         if (str.empty() || str[0] == 'q' || str[0] == 'Q')
  76             break;
  77
  78         double n;
  79         if (client::adder(str.begin(), str.end(), n))
  80         {
  81             std::cout << "-------------------------\n";
  82             std::cout << "Parsing succeeded\n";
  83             std::cout << str << " Parses OK: " << std::endl;
  84
  85             std::cout << "sum = " << n;
  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 }