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 58