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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 | /// \file | |
12 | /// \brief base dimensions (mass, length, time...). | |
13 | /// \details base dimension definition registration. | |
14 | ||
15 | #ifndef BOOST_UNITS_BASE_DIMENSION_HPP | |
16 | #define BOOST_UNITS_BASE_DIMENSION_HPP | |
17 | ||
18 | #include <boost/units/config.hpp> | |
19 | #include <boost/units/dim.hpp> | |
20 | #include <boost/units/static_rational.hpp> | |
21 | #include <boost/units/units_fwd.hpp> | |
22 | #include <boost/units/detail/dimension_list.hpp> | |
23 | #include <boost/units/detail/ordinal.hpp> | |
24 | #include <boost/units/detail/prevent_redefinition.hpp> | |
25 | ||
26 | namespace boost { | |
27 | ||
28 | namespace units { | |
29 | ||
30 | /// This must be in namespace boost::units so that ADL | |
31 | /// will work with friend functions defined inline. | |
32 | /// INTERNAL ONLY | |
33 | template<long N> struct base_dimension_ordinal { }; | |
34 | ||
35 | /// INTERNAL ONLY | |
36 | template<class T, long N> struct base_dimension_pair { }; | |
37 | ||
38 | /// INTERNAL ONLY | |
39 | template<class T, long N> | |
40 | struct check_base_dimension { | |
41 | enum { | |
42 | value = | |
43 | sizeof(boost_units_is_registered(units::base_dimension_ordinal<N>())) == sizeof(detail::yes) && | |
44 | sizeof(boost_units_is_registered(units::base_dimension_pair<T, N>())) != sizeof(detail::yes) | |
45 | }; | |
46 | }; | |
47 | ||
48 | /// Defines a base dimension. To define a dimension you need to provide | |
49 | /// the derived class (CRTP) and a unique integer. | |
50 | /// @code | |
51 | /// struct my_dimension : boost::units::base_dimension<my_dimension, 1> {}; | |
52 | /// @endcode | |
53 | /// It is designed so that you will get an error message if you try | |
54 | /// to use the same value in multiple definitions. | |
55 | template<class Derived, | |
56 | long N | |
57 | #if !defined(BOOST_UNITS_DOXYGEN) && !defined(__BORLANDC__) | |
58 | , | |
59 | class = typename detail::ordinal_has_already_been_defined< | |
60 | check_base_dimension<Derived, N>::value | |
61 | >::type | |
62 | #endif | |
63 | > | |
64 | class base_dimension : | |
65 | public ordinal<N> | |
66 | { | |
67 | public: | |
68 | /// INTERNAL ONLY | |
69 | typedef base_dimension this_type; | |
70 | /// A convenience typedef. Equivalent to boost::units::derived_dimension<Derived,1>::type. | |
71 | #ifndef BOOST_UNITS_DOXYGEN | |
72 | typedef list<dim<Derived,static_rational<1> >, dimensionless_type> dimension_type; | |
73 | #else | |
74 | typedef detail::unspecified dimension_type; | |
75 | #endif | |
76 | /// Provided for mpl compatability. | |
77 | typedef Derived type; | |
78 | ||
79 | private: | |
80 | /// Check for C++0x. In C++0x, we have to have identical | |
81 | /// arguments but a different return type to trigger an | |
82 | /// error. Note that this is only needed for clang as | |
83 | /// check_base_dimension will trigger an error earlier | |
84 | /// for compilers with less strict name lookup. | |
85 | /// INTERNAL ONLY | |
11fdf7f2 | 86 | friend BOOST_CONSTEXPR Derived* |
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87 | check_double_register(const units::base_dimension_ordinal<N>&) |
88 | { return(0); } | |
89 | ||
90 | /// Register this ordinal | |
91 | /// INTERNAL ONLY | |
11fdf7f2 | 92 | friend BOOST_CONSTEXPR detail::yes |
7c673cae | 93 | boost_units_is_registered(const units::base_dimension_ordinal<N>&) |
11fdf7f2 | 94 | { return(detail::yes()); } |
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95 | |
96 | /// But make sure we can identify the current instantiation! | |
97 | /// INTERNAL ONLY | |
11fdf7f2 | 98 | friend BOOST_CONSTEXPR detail::yes |
7c673cae | 99 | boost_units_is_registered(const units::base_dimension_pair<Derived, N>&) |
11fdf7f2 | 100 | { return(detail::yes()); } |
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101 | }; |
102 | ||
103 | } // namespace units | |
104 | ||
105 | } // namespace boost | |
106 | ||
107 | #endif // BOOST_UNITS_BASE_DIMENSION_HPP |