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) 2007-2008 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_DIM_HPP
12#define BOOST_UNITS_DIM_HPP
13
14#include <boost/static_assert.hpp>
15
16#include <boost/type_traits/is_same.hpp>
17
18#include <boost/mpl/arithmetic.hpp>
19
20#include <boost/units/config.hpp>
21#include <boost/units/static_rational.hpp>
22#include <boost/units/detail/dim_impl.hpp>
23
24/// \file dim.hpp
25/// \brief Handling of fundamental dimension/exponent pairs.
26
27namespace boost {
28
29namespace units {
30
31namespace detail {
32
33struct dim_tag { };
34
35}
36
37/// \brief Dimension tag/exponent pair for a single fundamental dimension.
38///
39/// \details
40/// The dim class represents a single dimension tag/dimension exponent pair.
41/// That is, @c dim<tag_type,value_type> is a pair where @c tag_type represents the
42/// fundamental dimension being represented and @c value_type represents the
43/// exponent of that fundamental dimension as a @c static_rational. @c tag_type must
44/// be a derived from a specialization of @c base_dimension.
45/// Specialization of the following Boost.MPL metafunctions are provided
46///
47/// - @c mpl::plus for two @c dims
48/// - @c mpl::minus for two @c dims
49/// - @c mpl::negate for a @c dim
50///
51/// These metafunctions all operate on the exponent, and require
52/// that the @c dim operands have the same base dimension tag.
53/// In addition, multiplication and division by @c static_rational
54/// is supported.
55///
56/// - @c mpl::times for a @c static_rational and a @c dim in either order
57/// - @c mpl::divides for a @c static_rational and a @c dim in either order
58///
59/// These metafunctions likewise operate on the exponent only.
60template<typename T,typename V>
61struct dim
62{
63 typedef dim type;
64 typedef detail::dim_tag tag;
65 typedef T tag_type;
66 typedef V value_type;
67};
68
69} // namespace units
70
71} // namespace boost
72
73#if BOOST_UNITS_HAS_BOOST_TYPEOF
74
75#include BOOST_TYPEOF_INCREMENT_REGISTRATION_GROUP()
76
77BOOST_TYPEOF_REGISTER_TEMPLATE(boost::units::dim, 2)
78
79#endif
80
81#ifndef BOOST_UNITS_DOXYGEN
82
83namespace boost {
84
85namespace mpl {
86
87// define MPL operators acting on dim<T,V>
88
89template<>
90struct plus_impl<boost::units::detail::dim_tag,boost::units::detail::dim_tag>
91{
92 template<class T0, class T1>
93 struct apply
94 {
95 BOOST_STATIC_ASSERT((boost::is_same<typename T0::tag_type,typename T1::tag_type>::value == true));
96 typedef boost::units::dim<typename T0::tag_type, typename mpl::plus<typename T0::value_type, typename T1::value_type>::type> type;
97 };
98};
99
100template<>
101struct minus_impl<boost::units::detail::dim_tag,boost::units::detail::dim_tag>
102{
103 template<class T0, class T1>
104 struct apply
105 {
106 BOOST_STATIC_ASSERT((boost::is_same<typename T0::tag_type,typename T1::tag_type>::value == true));
107 typedef boost::units::dim<typename T0::tag_type, typename mpl::minus<typename T0::value_type, typename T1::value_type>::type> type;
108 };
109};
110
111template<>
112struct times_impl<boost::units::detail::dim_tag,boost::units::detail::static_rational_tag>
113{
114 template<class T0, class T1>
115 struct apply
116 {
117 typedef boost::units::dim<typename T0::tag_type, typename mpl::times<typename T0::value_type, T1>::type> type;
118 };
119};
120
121template<>
122struct times_impl<boost::units::detail::static_rational_tag,boost::units::detail::dim_tag>
123{
124 template<class T0, class T1>
125 struct apply
126 {
127 typedef boost::units::dim<typename T1::tag_type, typename mpl::times<T0, typename T1::value_type>::type> type;
128 };
129};
130
131template<>
132struct divides_impl<boost::units::detail::dim_tag,boost::units::detail::static_rational_tag>
133{
134 template<class T0, class T1>
135 struct apply
136 {
137 typedef boost::units::dim<typename T0::tag_type, typename mpl::divides<typename T0::value_type, T1>::type> type;
138 };
139};
140
141template<>
142struct divides_impl<boost::units::detail::static_rational_tag,boost::units::detail::dim_tag>
143{
144 template<class T0, class T1>
145 struct apply
146 {
147 typedef boost::units::dim<typename T1::tag_type, typename mpl::divides<T0, typename T1::value_type>::type> type;
148 };
149};
150
151template<>
152struct negate_impl<boost::units::detail::dim_tag>
153{
154 template<class T0>
155 struct apply
156 {
157 typedef boost::units::dim<typename T0::tag_type,typename mpl::negate<typename T0::value_type>::type> type;
158 };
159};
160
161} // namespace mpl
162
163} // namespace boost
164
165#endif
166
167#endif // BOOST_UNITS_DIM_HPP
168

source code of boost/libs/units/include/boost/units/dim.hpp