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_HPP
15#define BOOST_GEOMETRY_CORE_TAG_HPP
16
17#include <boost/mpl/assert.hpp>
18
19#include <boost/geometry/core/tags.hpp>
20#include <boost/geometry/util/bare_type.hpp>
21
22
23namespace boost { namespace geometry
24{
25
26namespace traits
27{
28
29/*!
30\brief Traits class to attach a tag to a geometry
31\details All geometries should implement a traits::tag<G>::type metafunction to indicate their
32 own geometry type.
33\ingroup traits
34\par Geometries:
35 - all geometries
36\par Specializations should provide:
37 - typedef XXX_tag type; (point_tag, box_tag, ...)
38\tparam Geometry geometry
39*/
40template <typename Geometry, typename Enable = void>
41struct tag
42{
43 typedef void type;
44};
45
46} // namespace traits
47
48
49
50/*!
51\brief \brief_meta{type, tag, \meta_geometry_type}
52\details With Boost.Geometry, tags are the driving force of the tag dispatching
53 mechanism. The tag metafunction is therefore used in every free function.
54\tparam Geometry \tparam_geometry
55\ingroup core
56
57\qbk{[include reference/core/tag.qbk]}
58*/
59template <typename Geometry>
60struct tag
61{
62 typedef typename traits::tag
63 <
64 typename geometry::util::bare_type<Geometry>::type
65 >::type type;
66};
67
68}} // namespace boost::geometry
69
70#endif // BOOST_GEOMETRY_CORE_TAG_HPP
71

source code of boost/boost/geometry/core/tag.hpp