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_DIMENSION_HPP
12#define BOOST_UNITS_DIMENSION_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/static_rational.hpp>
21#include <boost/units/detail/dimension_list.hpp>
22#include <boost/units/detail/dimension_impl.hpp>
23
24/// \file
25/// \brief Core metaprogramming utilities for compile-time dimensional analysis.
26
27namespace boost {
28
29namespace units {
30
31/// Reduce dimension list to cardinal form. This algorithm collapses duplicate
32/// base dimension tags and sorts the resulting list by the tag ordinal value.
33/// Dimension lists that resolve to the same dimension are guaranteed to be
34/// represented by an identical type.
35///
36/// The argument should be an MPL forward sequence containing instances
37/// of the @c dim template.
38///
39/// The result is also an MPL forward sequence. It also supports the
40/// following metafunctions to allow use as a dimension.
41///
42/// - @c mpl::plus is defined only on two equal dimensions and returns the argument unchanged.
43/// - @c mpl::minus is defined only for two equal dimensions and returns the argument unchanged.
44/// - @c mpl::negate will return its argument unchanged.
45/// - @c mpl::times is defined for any dimensions and adds corresponding exponents.
46/// - @c mpl::divides is defined for any dimensions and subtracts the exponents of the
47/// right had argument from the corresponding exponents of the left had argument.
48/// Missing base dimension tags are assumed to have an exponent of zero.
49/// - @c static_power takes a dimension and a static_rational and multiplies all
50/// the exponents of the dimension by the static_rational.
51/// - @c static_root takes a dimension and a static_rational and divides all
52/// the exponents of the dimension by the static_rational.
53template<typename Seq>
54struct make_dimension_list
55{
56 typedef typename detail::sort_dims<Seq>::type type;
57};
58
59/// Raise a dimension list to a scalar power.
60template<typename DL,typename Ex>
61struct static_power
62{
63 typedef typename detail::static_power_impl<DL::size::value>::template apply<
64 DL,
65 Ex
66 >::type type;
67};
68
69/// Take a scalar root of a dimension list.
70template<typename DL,typename Rt>
71struct static_root
72{
73 typedef typename detail::static_root_impl<DL::size::value>::template apply<
74 DL,
75 Rt
76 >::type type;
77};
78
79} // namespace units
80
81#ifndef BOOST_UNITS_DOXYGEN
82
83namespace mpl {
84
85template<>
86struct plus_impl<boost::units::detail::dimension_list_tag,boost::units::detail::dimension_list_tag>
87{
88 template<class T0, class T1>
89 struct apply
90 {
91 BOOST_STATIC_ASSERT((boost::is_same<T0,T1>::value == true));
92 typedef T0 type;
93 };
94};
95
96template<>
97struct minus_impl<boost::units::detail::dimension_list_tag,boost::units::detail::dimension_list_tag>
98{
99 template<class T0, class T1>
100 struct apply
101 {
102 BOOST_STATIC_ASSERT((boost::is_same<T0,T1>::value == true));
103 typedef T0 type;
104 };
105};
106
107template<>
108struct times_impl<boost::units::detail::dimension_list_tag,boost::units::detail::dimension_list_tag>
109{
110 template<class T0, class T1>
111 struct apply
112 {
113 typedef typename boost::units::detail::merge_dimensions<T0,T1>::type type;
114 };
115};
116
117template<>
118struct divides_impl<boost::units::detail::dimension_list_tag,boost::units::detail::dimension_list_tag>
119{
120 template<class T0, class T1>
121 struct apply
122 {
123 typedef typename boost::units::detail::merge_dimensions<
124 T0,
125 typename boost::units::detail::static_inverse_impl<
126 T1::size::value
127 >::template apply<
128 T1
129 >::type
130 >::type type;
131 };
132};
133
134template<>
135struct negate_impl<boost::units::detail::dimension_list_tag>
136{
137 template<class T0>
138 struct apply
139 {
140 typedef T0 type;
141 };
142};
143
144} // namespace mpl
145
146#endif
147
148} // namespace boost
149
150#endif // BOOST_UNITS_DIMENSION_HPP
151

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