ceph/src/boost/boost/geometry/core/tag_cast.hpp

   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 // This file was modified by Oracle on 2020.
   8 // Modifications copyright (c) 2020, Oracle and/or its affiliates.
   9 // Contributed and/or modified by Adam Wulkiewicz, on behalf of Oracle
  10
  11 // Parts of Boost.Geometry are redesigned from Geodan's Geographic Library
  12 // (geolib/GGL), copyright (c) 1995-2010 Geodan, Amsterdam, the Netherlands.
  13
  14 // Use, modification and distribution is subject to the Boost Software License,
  15 // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
  16 // http://www.boost.org/LICENSE_1_0.txt)
  17
  18 #ifndef BOOST_GEOMETRY_CORE_TAG_CAST_HPP
  19 #define BOOST_GEOMETRY_CORE_TAG_CAST_HPP
  20
  21
  22 #include <type_traits>
  23
  24
  25 namespace boost { namespace geometry
  26 {
  27
  28 /*!
  29 \brief Metafunction defining a type being either the specified tag, or one
  30     of the specified basetags if the type inherits from them.
  31 \details Tags can inherit each other. A multi_point inherits, for example,
  32     both the multi_tag and the pointlike_tag. Often behaviour can be shared
  33     between different geometry types. A tag, found by the metafunction tag,
  34     can be casted to a more basic tag, and then dispatched by that tag.
  35 \ingroup core
  36 \tparam Tag The tag to be casted to one of the base tags
  37 \tparam BaseTags Base tags
  38
  39 \qbk{[include reference/core/tag_cast.qbk]}
  40 */
  41 template <typename Tag, typename ...BaseTags>
  42 struct tag_cast
  43 {
  44     typedef Tag type;
  45 };
  46
  47 #ifndef DOXYGEN_NO_SPECIALIZATIONS
  48
  49 template <typename Tag, typename BaseTag, typename ...BaseTags>
  50 struct tag_cast<Tag, BaseTag, BaseTags...>
  51 {
  52     typedef std::conditional_t
  53         <
  54           std::is_base_of<BaseTag, Tag>::value,
  55           BaseTag,
  56           typename tag_cast
  57             <
  58                 Tag, BaseTags...
  59             >::type
  60         > type;
  61 };
  62
  63 #endif // DOXYGEN_NO_SPECIALIZATIONS
  64
  65
  66 }} // namespace boost::geometry
  67
  68 #endif // BOOST_GEOMETRY_CORE_TAG_CAST_HPP