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 #if defined(BOOST_NO_CXX11_CONSTEXPR) || defined(BOOST_UNITS_DOXYGEN) 17 /// A convenience macro that allows definition of static 18 /// constants in headers in an ODR-safe way. 19 # define BOOST_UNITS_STATIC_CONSTANT(name, type) \ 20 template<bool b> \ 21 struct name##_instance_t \ 22 { \ 23 static const type instance; \ 24 }; \ 25 \ 26 namespace \ 27 { \ 28 static const type& name = name##_instance_t<true>::instance; \ 29 } \ 30 \ 31 template<bool b> \ 32 const type name##_instance_t<b>::instance 33 #else 34 # define BOOST_UNITS_STATIC_CONSTANT(name, type) \ 35 BOOST_STATIC_CONSTEXPR type name 36 #endif 37 38 /// A convenience macro for static constants with auto 39 /// type deduction. 40 #if BOOST_UNITS_HAS_TYPEOF 41 42 #if BOOST_UNITS_HAS_BOOST_TYPEOF 43 44 #define BOOST_UNITS_AUTO_STATIC_CONSTANT(name, value) \ 45 BOOST_TYPEOF_NESTED_TYPEDEF(name##_nested_t, value) \ 46 BOOST_UNITS_STATIC_CONSTANT(name, name##_nested_t::type) = (value) 47 48 #elif BOOST_UNITS_HAS_MWERKS_TYPEOF 49 50 #define BOOST_UNITS_AUTO_STATIC_CONSTANT(name, value) \ 51 BOOST_UNITS_STATIC_CONSTANT(name, __typeof__(value)) = (value) 52 53 #elif BOOST_UNITS_HAS_GNU_TYPEOF 54 55 #define BOOST_UNITS_AUTO_STATIC_CONSTANT(name, value) \ 56 BOOST_UNITS_STATIC_CONSTANT(name, typeof(value)) = (value) 57 58 #endif // BOOST_UNITS_HAS_BOOST_TYPEOF 59 60 #endif // BOOST_UNITS_HAS_TYPEOF 61 62 #endif // BOOST_UNITS_STATIC_CONSTANT_HPP 63