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1 | // Boost.Geometry (aka GGL, Generic Geometry Library) |
2 | ||
3 | // Copyright (c) 2007-2012 Barend Gehrels, Amsterdam, the Netherlands. | |
4 | // Copyright (c) 2008-2012 Bruno Lalande, Paris, France. | |
5 | // Copyright (c) 2009-2012 Mateusz Loskot, London, UK. | |
6 | ||
7 | // Parts of Boost.Geometry are redesigned from Geodan's Geographic Library | |
8 | // (geolib/GGL), copyright (c) 1995-2010 Geodan, Amsterdam, the Netherlands. | |
9 | ||
10 | // Use, modification and distribution is subject to the Boost Software License, | |
11 | // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at | |
12 | // http://www.boost.org/LICENSE_1_0.txt) | |
13 | ||
14 | #ifndef BOOST_GEOMETRY_CORE_TAG_CAST_HPP | |
15 | #define BOOST_GEOMETRY_CORE_TAG_CAST_HPP | |
16 | ||
17 | ||
18 | #include <boost/mpl/if.hpp> | |
19 | #include <boost/type_traits/is_base_of.hpp> | |
20 | ||
21 | namespace boost { namespace geometry | |
22 | { | |
23 | ||
24 | /*! | |
25 | \brief Metafunction defining a type being either the specified tag, or one | |
26 | of the specified basetags if the type inherits from them. | |
27 | \details Tags can inherit each other. A multi_point inherits, for example, | |
28 | both the multi_tag and the pointlike_tag. Often behaviour can be shared | |
29 | between different geometry types. A tag, found by the metafunction tag, | |
30 | can be casted to a more basic tag, and then dispatched by that tag. | |
31 | \ingroup core | |
32 | \tparam Tag The tag to be casted to one of the base tags | |
33 | \tparam BaseTag First base tag | |
34 | \tparam BaseTag2 Optional second base tag | |
35 | \tparam BaseTag3 Optional third base tag | |
36 | \tparam BaseTag4 Optional fourth base tag | |
37 | \tparam BaseTag5 Optional fifth base tag | |
38 | \tparam BaseTag6 Optional sixth base tag | |
39 | \tparam BaseTag7 Optional seventh base tag | |
40 | ||
41 | \qbk{[include reference/core/tag_cast.qbk]} | |
42 | */ | |
43 | template | |
44 | < | |
45 | typename Tag, | |
46 | typename BaseTag, | |
47 | typename BaseTag2 = void, | |
48 | typename BaseTag3 = void, | |
49 | typename BaseTag4 = void, | |
50 | typename BaseTag5 = void, | |
51 | typename BaseTag6 = void, | |
52 | typename BaseTag7 = void | |
53 | > | |
54 | struct tag_cast | |
55 | { | |
56 | typedef typename boost::mpl::if_ | |
57 | < | |
58 | typename boost::is_base_of<BaseTag, Tag>::type, | |
59 | BaseTag, | |
60 | // Try next one in line: | |
61 | typename tag_cast | |
62 | < | |
63 | Tag, BaseTag2, BaseTag3, BaseTag4, | |
64 | BaseTag5, BaseTag6, BaseTag7, void | |
65 | >::type | |
66 | >::type type; | |
67 | }; | |
68 | ||
69 | #ifndef DOXYGEN_NO_SPECIALIZATIONS | |
70 | ||
71 | // Specialization for last one | |
72 | template <typename Tag> | |
73 | struct tag_cast<Tag, void, void, void, void, void, void, void> | |
74 | { | |
75 | // If not found, take specified tag, so do not cast | |
76 | typedef Tag type; | |
77 | }; | |
78 | ||
79 | #endif // DOXYGEN_NO_SPECIALIZATIONS | |
80 | ||
81 | ||
82 | }} // namespace boost::geometry | |
83 | ||
84 | #endif // BOOST_GEOMETRY_CORE_TAG_CAST_HPP |