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1 | // Boost.Units - A C++ library for zero-overhead dimensional analysis and |
2 | // unit/quantity manipulation and conversion | |
3 | // | |
4 | // Copyright (C) 2003-2008 Matthias Christian Schabel | |
5 | // Copyright (C) 2008 Steven Watanabe | |
6 | // | |
7 | // Distributed under the Boost Software License, Version 1.0. (See | |
8 | // accompanying file LICENSE_1_0.txt or copy at | |
9 | // http://www.boost.org/LICENSE_1_0.txt) | |
10 | ||
11 | #ifndef BOOST_UNITS_STATIC_CONSTANT_HPP | |
12 | #define BOOST_UNITS_STATIC_CONSTANT_HPP | |
13 | ||
14 | #include <boost/units/config.hpp> | |
15 | ||
16 | /// A convenience macro that allows definition of static | |
17 | /// constants in headers in an ODR-safe way. | |
18 | #define BOOST_UNITS_STATIC_CONSTANT(name, type) \ | |
19 | template<bool b> \ | |
20 | struct name##_instance_t \ | |
21 | { \ | |
22 | static const type instance; \ | |
23 | }; \ | |
24 | \ | |
25 | namespace \ | |
26 | { \ | |
27 | static const type& name = name##_instance_t<true>::instance; \ | |
28 | } \ | |
29 | \ | |
30 | template<bool b> \ | |
31 | const type name##_instance_t<b>::instance | |
32 | ||
33 | /// A convenience macro for static constants with auto | |
34 | /// type deduction. | |
35 | #if BOOST_UNITS_HAS_TYPEOF | |
36 | ||
37 | #if BOOST_UNITS_HAS_BOOST_TYPEOF | |
38 | ||
39 | #define BOOST_UNITS_AUTO_STATIC_CONSTANT(name, value) \ | |
40 | BOOST_TYPEOF_NESTED_TYPEDEF(name##_nested_t, value) \ | |
41 | BOOST_UNITS_STATIC_CONSTANT(name, name##_nested_t::type) = (value) | |
42 | ||
43 | #elif BOOST_UNITS_HAS_MWERKS_TYPEOF | |
44 | ||
45 | #define BOOST_UNITS_AUTO_STATIC_CONSTANT(name, value) \ | |
46 | BOOST_UNITS_STATIC_CONSTANT(name, __typeof__(value)) = (value) | |
47 | ||
48 | #elif BOOST_UNITS_HAS_GNU_TYPEOF | |
49 | ||
50 | #define BOOST_UNITS_AUTO_STATIC_CONSTANT(name, value) \ | |
51 | BOOST_UNITS_STATIC_CONSTANT(name, typeof(value)) = (value) | |
52 | ||
53 | #endif // BOOST_UNITS_HAS_BOOST_TYPEOF | |
54 | ||
55 | #endif // BOOST_UNITS_HAS_TYPEOF | |
56 | ||
57 | #endif // BOOST_UNITS_STATIC_CONSTANT_HPP |