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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 |