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// Copyright Abel Sinkovics (abel@sinkovics.hu) 2015.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
#include <boost/metaparse/string.hpp>
#include <boost/metaparse/sequence_apply.hpp>
#include <boost/metaparse/last_of.hpp>
#include <boost/metaparse/int_.hpp>
#include <boost/metaparse/token.hpp>
#include <boost/metaparse/lit_c.hpp>
#include <boost/metaparse/entire_input.hpp>
#include <boost/metaparse/build_parser.hpp>
#include <boost/rational.hpp>
#include <boost/config.hpp>
#include <iostream>
using boost::metaparse::sequence_apply2;
using boost::metaparse::last_of;
using boost::metaparse::int_;
using boost::metaparse::token;
using boost::metaparse::lit_c;
using boost::metaparse::entire_input;
using boost::metaparse::build_parser;
template <class Num, class Denom>
struct rational
{
typedef rational type;
static boost::rational<int> run()
{
return boost::rational<int>(Num::type::value, Denom::type::value);
}
};
typedef
sequence_apply2<
rational,
token<int_>,
last_of<lit_c<'/'>, token<int_> >
>
rational_grammar;
typedef build_parser<entire_input<rational_grammar> > rational_parser;
#ifdef RATIONAL
# error RATIONAL already defined
#endif
#define RATIONAL(s) \
(::rational_parser::apply<BOOST_METAPARSE_STRING(s)>::type::run())
#if BOOST_METAPARSE_STD < 2011
int main()
{
std::cout << "Please use a compiler that supports constexpr" << std::endl;
}
#else
int main()
{
const boost::rational<int> r1 = RATIONAL("1/3");
const boost::rational<int> r2 = RATIONAL("4/4");
const boost::rational<int> r3 = RATIONAL("13/11");
std::cout
<< r1 << std::endl
<< r2 << std::endl
<< r3 << std::endl;
}
#endif
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