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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) 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_DETAIL_PUSH_FRONT_OR_ADD_HPP | |
12 | #define BOOST_UNITS_DETAIL_PUSH_FRONT_OR_ADD_HPP | |
13 | ||
14 | #include <boost/mpl/plus.hpp> | |
15 | #include <boost/mpl/front.hpp> | |
16 | #include <boost/mpl/push_front.hpp> | |
17 | #include <boost/mpl/pop_front.hpp> | |
18 | #include <boost/type_traits/is_same.hpp> | |
19 | ||
20 | #include <boost/units/units_fwd.hpp> | |
21 | #include <boost/units/detail/push_front_if.hpp> | |
22 | ||
23 | namespace boost { | |
24 | ||
25 | namespace units { | |
26 | ||
27 | template<class Item, class Next> | |
28 | struct list; | |
29 | ||
30 | namespace detail { | |
31 | ||
32 | template<class T> | |
33 | struct is_empty_dim; | |
34 | ||
35 | /// add an instantiation of dim to Sequence. | |
36 | template<bool> | |
37 | struct push_front_or_add_impl; | |
38 | ||
39 | template<> | |
40 | struct push_front_or_add_impl<true> | |
41 | { | |
42 | template<typename Sequence, typename T> | |
43 | struct apply | |
44 | { | |
45 | typedef typename mpl::plus<T, typename Sequence::item>::type item; | |
46 | typedef typename push_front_if<!is_empty_dim<item>::value>::template apply< | |
47 | typename Sequence::next, | |
48 | item | |
49 | > type; | |
50 | }; | |
51 | }; | |
52 | ||
53 | template<> | |
54 | struct push_front_or_add_impl<false> | |
55 | { | |
56 | template<typename Sequence, typename T> | |
57 | struct apply | |
58 | { | |
59 | typedef list<T, Sequence> type; | |
60 | }; | |
61 | }; | |
62 | ||
63 | template<typename Sequence, typename T> | |
64 | struct push_front_or_add | |
65 | { | |
66 | typedef typename push_front_or_add_impl<boost::is_same<typename T::tag_type, typename Sequence::item::tag_type>::value>::template apply< | |
67 | Sequence, | |
68 | T | |
69 | >::type type; | |
70 | }; | |
71 | ||
72 | template<typename T> | |
73 | struct push_front_or_add<dimensionless_type, T> | |
74 | { | |
75 | typedef list<T, dimensionless_type> type; | |
76 | }; | |
77 | ||
78 | } // namespace detail | |
79 | ||
80 | } // namespace units | |
81 | ||
82 | } // namespace boost | |
83 | ||
84 | #endif |