// 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_DIM_IMPL_HPP
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#define BOOST_UNITS_DIM_IMPL_HPP
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#include <boost/mpl/bool.hpp>
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#include <boost/mpl/less.hpp>
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#include <boost/units/units_fwd.hpp>
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/// \file
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/// \brief Class encapsulating a dimension tag/value pair
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namespace boost {
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namespace units {
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namespace detail {
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struct dim_tag;
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}
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}
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namespace mpl {
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/// Less than comparison for sorting @c dim.
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template<>
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struct less_impl<boost::units::detail::dim_tag, boost::units::detail::dim_tag>
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{
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template<class T0, class T1>
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struct apply : mpl::less<typename T0::tag_type, typename T1::tag_type> {};
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};
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}
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namespace units {
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template<class Tag, class Exponent>
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struct dim;
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template<long N, long D>
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class static_rational;
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namespace detail {
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/// Extract @c tag_type from a @c dim.
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template<typename T>
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struct get_tag
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{
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typedef typename T::tag_type type;
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};
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/// Extract @c value_type from a @c dim.
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template<typename T>
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struct get_value
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{
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typedef typename T::value_type type;
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};
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/// Determine if a @c dim is empty (has a zero exponent).
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template<class T>
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struct is_empty_dim;
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template<typename T>
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struct is_empty_dim< dim<T, static_rational<0, 1> > > :
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mpl::true_
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{ };
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template<typename T, typename V>
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struct is_empty_dim< dim<T, V> > :
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mpl::false_
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{ };
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} // namespace detail
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} // namespace units
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} // namespace boost
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#endif // BOOST_UNITS_DIM_IMPL_HPP
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