ceph/src/boost/libs/metaparse/example/minimal_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/entire_input.hpp>
  13 #include <boost/metaparse/build_parser.hpp>
  14
  15 #include <boost/rational.hpp>
  16
  17 #include <boost/config.hpp>
  18
  19 #include <iostream>
  20
  21 using boost::metaparse::sequence_apply2;
  22 using boost::metaparse::last_of;
  23 using boost::metaparse::int_;
  24 using boost::metaparse::token;
  25 using boost::metaparse::lit_c;
  26 using boost::metaparse::entire_input;
  27 using boost::metaparse::build_parser;
  28
  29 template <class Num, class Denom>
  30 struct rational
  31 {
  32   typedef rational type;
  33
  34   static boost::rational<int> run()
  35   {
  36     return boost::rational<int>(Num::type::value, Denom::type::value);
  37   }
  38 };
  39
  40 typedef
  41   sequence_apply2<
  42     rational,
  43
  44     token<int_>,
  45     last_of<lit_c<'/'>, token<int_> >
  46   >
  47   rational_grammar;
  48
  49 typedef build_parser<entire_input<rational_grammar> > rational_parser;
  50
  51 #ifdef RATIONAL
  52 #  error RATIONAL already defined
  53 #endif
  54 #define RATIONAL(s) \
  55   (::rational_parser::apply<BOOST_METAPARSE_STRING(s)>::type::run())
  56
  57 #ifdef BOOST_NO_CXX11_CONSTEXPR
  58
  59 int main()
  60 {
  61   std::cout << "Please use a compiler that supports constexpr" << std::endl;
  62 }
  63
  64 #else
  65
  66 int main()
  67 {
  68   const boost::rational<int> r1 = RATIONAL("1/3");
  69   const boost::rational<int> r2 = RATIONAL("4/4");
  70   const boost::rational<int> r3 = RATIONAL("13/11");
  71
  72   std::cout
  73     << r1 << std::endl
  74     << r2 << std::endl
  75     << r3 << std::endl;
  76 }
  77
  78 #endif
  79