58 lines
2.3 KiB
C++
58 lines
2.3 KiB
C++
// Boost.Units - A C++ library for zero-overhead dimensional analysis and
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// unit/quantity manipulation and conversion
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//
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// Copyright (C) 2003-2008 Matthias Christian Schabel
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// Copyright (C) 2008 Steven Watanabe
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//
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// Distributed under the Boost Software License, Version 1.0. (See
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// accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_UNITS_STATIC_CONSTANT_HPP
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#define BOOST_UNITS_STATIC_CONSTANT_HPP
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#include <boost/units/config.hpp>
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/// A convenience macro that allows definition of static
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/// constants in headers in an ODR-safe way.
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#define BOOST_UNITS_STATIC_CONSTANT(name, type) \
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template<bool b> \
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struct name##_instance_t \
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{ \
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static const type instance; \
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}; \
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\
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namespace \
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{ \
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static const type& name = name##_instance_t<true>::instance; \
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} \
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\
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template<bool b> \
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const type name##_instance_t<b>::instance
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/// A convenience macro for static constants with auto
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/// type deduction.
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#if BOOST_UNITS_HAS_TYPEOF
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#if BOOST_UNITS_HAS_BOOST_TYPEOF
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#define BOOST_UNITS_AUTO_STATIC_CONSTANT(name, value) \
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BOOST_TYPEOF_NESTED_TYPEDEF(name##_nested_t, value) \
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BOOST_UNITS_STATIC_CONSTANT(name, name##_nested_t::type) = (value)
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#elif BOOST_UNITS_HAS_MWERKS_TYPEOF
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#define BOOST_UNITS_AUTO_STATIC_CONSTANT(name, value) \
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BOOST_UNITS_STATIC_CONSTANT(name, __typeof__(value)) = (value)
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#elif BOOST_UNITS_HAS_GNU_TYPEOF
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#define BOOST_UNITS_AUTO_STATIC_CONSTANT(name, value) \
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BOOST_UNITS_STATIC_CONSTANT(name, typeof(value)) = (value)
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#endif // BOOST_UNITS_HAS_BOOST_TYPEOF
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#endif // BOOST_UNITS_HAS_TYPEOF
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#endif // BOOST_UNITS_STATIC_CONSTANT_HPP
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