ceph/src/boost/libs/metaparse/example/rational/main.cpp

   1 // Copyright Abel Sinkovics (abel@sinkovics.hu)  2015.
   2 // Distributed under the Boost Software License, Version 1.0.
   3 //    (See accompanying file LICENSE_1_0.txt or copy at
   4 //          http://www.boost.org/LICENSE_1_0.txt)
   5
   6 #include <boost/metaparse/string.hpp>
   7 #include <boost/metaparse/sequence_apply.hpp>
   8 #include <boost/metaparse/last_of.hpp>
   9 #include <boost/metaparse/int_.hpp>
  10 #include <boost/metaparse/token.hpp>
  11 #include <boost/metaparse/lit_c.hpp>
  12 #include <boost/metaparse/one_of.hpp>
  13 #include <boost/metaparse/empty.hpp>
  14 #include <boost/metaparse/entire_input.hpp>
  15 #include <boost/metaparse/build_parser.hpp>
  16
  17 #include <boost/rational.hpp>
  18
  19 #include <boost/config.hpp>
  20
  21 #include <boost/mpl/int.hpp>
  22
  23 #include <iostream>
  24
  25 using boost::metaparse::sequence_apply2;
  26 using boost::metaparse::last_of;
  27 using boost::metaparse::int_;
  28 using boost::metaparse::token;
  29 using boost::metaparse::lit_c;
  30 using boost::metaparse::one_of;
  31 using boost::metaparse::empty;
  32 using boost::metaparse::entire_input;
  33 using boost::metaparse::build_parser;
  34
  35 template <class Num, class Denom>
  36 struct rational
  37 {
  38   typedef rational type;
  39
  40   static boost::rational<int> run()
  41   {
  42     return boost::rational<int>(Num::type::value, Denom::type::value);
  43   }
  44 };
  45
  46 typedef
  47   sequence_apply2<
  48     rational,
  49
  50     token<int_>,
  51     one_of<
  52       last_of<lit_c<'/'>, token<int_> >,
  53       empty<boost::mpl::int_<1> >
  54     >
  55   >
  56   rational_grammar;
  57
  58 typedef build_parser<entire_input<rational_grammar> > rational_parser;
  59
  60 #ifdef RATIONAL
  61 #  error RATIONAL already defined
  62 #endif
  63 #define RATIONAL(s) \
  64   (::rational_parser::apply<BOOST_METAPARSE_STRING(s)>::type::run())
  65
  66 #ifdef BOOST_NO_CXX11_CONSTEXPR
  67
  68 int main()
  69 {
  70   std::cout << "Please use a compiler that supports constexpr" << std::endl;
  71 }
  72
  73 #else
  74
  75 int main()
  76 {
  77   const boost::rational<int> r1 = RATIONAL("1/3");
  78   const boost::rational<int> r2 = RATIONAL("4/4");
  79   const boost::rational<int> r3 = RATIONAL("1");
  80   const boost::rational<int> r4 = RATIONAL("13/11");
  81
  82   // Uncommenting the following line generates a compilation error. On a
  83   // number of platforms the error report contains the following (or something
  84   // similar):
  85   // x__________________PARSING_FAILED__________________x<1, 3, digit_expected>
  86   // where 1, 3 is the location of the error inside the string literal.
  87 //  const boost::rational<int> r5 = RATIONAL("7/");
  88
  89   std::cout
  90     << r1 << std::endl
  91     << r2 << std::endl
  92     << r3 << std::endl
  93     << r4 << std::endl;
  94 }
  95
  96 #endif
  97