151 lines
4.4 KiB
C++
151 lines
4.4 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) 2007-2008 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_DIMENSION_HPP
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#define BOOST_UNITS_DIMENSION_HPP
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#include <boost/static_assert.hpp>
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#include <boost/type_traits/is_same.hpp>
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#include <boost/mpl/arithmetic.hpp>
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#include <boost/units/static_rational.hpp>
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#include <boost/units/detail/dimension_list.hpp>
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#include <boost/units/detail/dimension_impl.hpp>
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/// \file
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/// \brief Core metaprogramming utilities for compile-time dimensional analysis.
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namespace boost {
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namespace units {
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/// Reduce dimension list to cardinal form. This algorithm collapses duplicate
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/// base dimension tags and sorts the resulting list by the tag ordinal value.
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/// Dimension lists that resolve to the same dimension are guaranteed to be
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/// represented by an identical type.
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///
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/// The argument should be an MPL forward sequence containing instances
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/// of the @c dim template.
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///
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/// The result is also an MPL forward sequence. It also supports the
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/// following metafunctions to allow use as a dimension.
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///
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/// - @c mpl::plus is defined only on two equal dimensions and returns the argument unchanged.
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/// - @c mpl::minus is defined only for two equal dimensions and returns the argument unchanged.
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/// - @c mpl::negate will return its argument unchanged.
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/// - @c mpl::times is defined for any dimensions and adds corresponding exponents.
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/// - @c mpl::divides is defined for any dimensions and subtracts the exponents of the
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/// right had argument from the corresponding exponents of the left had argument.
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/// Missing base dimension tags are assumed to have an exponent of zero.
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/// - @c static_power takes a dimension and a static_rational and multiplies all
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/// the exponents of the dimension by the static_rational.
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/// - @c static_root takes a dimension and a static_rational and divides all
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/// the exponents of the dimension by the static_rational.
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template<typename Seq>
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struct make_dimension_list
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{
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typedef typename detail::sort_dims<Seq>::type type;
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};
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/// Raise a dimension list to a scalar power.
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template<typename DL,typename Ex>
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struct static_power
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{
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typedef typename detail::static_power_impl<DL::size::value>::template apply<
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DL,
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Ex
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>::type type;
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};
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/// Take a scalar root of a dimension list.
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template<typename DL,typename Rt>
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struct static_root
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{
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typedef typename detail::static_root_impl<DL::size::value>::template apply<
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DL,
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Rt
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>::type type;
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};
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} // namespace units
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#ifndef BOOST_UNITS_DOXYGEN
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namespace mpl {
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template<>
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struct plus_impl<boost::units::detail::dimension_list_tag,boost::units::detail::dimension_list_tag>
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{
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template<class T0, class T1>
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struct apply
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{
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BOOST_STATIC_ASSERT((boost::is_same<T0,T1>::value == true));
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typedef T0 type;
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};
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};
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template<>
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struct minus_impl<boost::units::detail::dimension_list_tag,boost::units::detail::dimension_list_tag>
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{
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template<class T0, class T1>
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struct apply
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{
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BOOST_STATIC_ASSERT((boost::is_same<T0,T1>::value == true));
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typedef T0 type;
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};
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};
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template<>
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struct times_impl<boost::units::detail::dimension_list_tag,boost::units::detail::dimension_list_tag>
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{
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template<class T0, class T1>
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struct apply
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{
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typedef typename boost::units::detail::merge_dimensions<T0,T1>::type type;
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};
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};
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template<>
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struct divides_impl<boost::units::detail::dimension_list_tag,boost::units::detail::dimension_list_tag>
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{
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template<class T0, class T1>
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struct apply
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{
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typedef typename boost::units::detail::merge_dimensions<
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T0,
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typename boost::units::detail::static_inverse_impl<
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T1::size::value
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>::template apply<
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T1
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>::type
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>::type type;
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};
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};
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template<>
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struct negate_impl<boost::units::detail::dimension_list_tag>
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{
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template<class T0>
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struct apply
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{
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typedef T0 type;
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};
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};
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} // namespace mpl
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#endif
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} // namespace boost
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#endif // BOOST_UNITS_DIMENSION_HPP
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