| // Boost.Geometry (aka GGL, Generic Geometry Library) |
| |
| // Copyright (c) 2007-2011 Barend Gehrels, Amsterdam, the Netherlands. |
| // Copyright (c) 2008-2011 Bruno Lalande, Paris, France. |
| // Copyright (c) 2009-2011 Mateusz Loskot, London, UK. |
| |
| // Parts of Boost.Geometry are redesigned from Geodan's Geographic Library |
| // (geolib/GGL), copyright (c) 1995-2010 Geodan, Amsterdam, the Netherlands. |
| |
| // Use, modification and distribution is subject to the Boost Software License, |
| // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at |
| // http://www.boost.org/LICENSE_1_0.txt) |
| |
| #ifndef BOOST_GEOMETRY_CORE_TAG_CAST_HPP |
| #define BOOST_GEOMETRY_CORE_TAG_CAST_HPP |
| |
| |
| #include <boost/mpl/if.hpp> |
| #include <boost/type_traits.hpp> |
| |
| namespace boost { namespace geometry |
| { |
| |
| /*! |
| \brief Metafunction defining a type being either the specified tag, or one |
| of the specified basetags if the type inherits from them. |
| \details Tags can inherit each other. A multi_point inherits, for example, |
| both the multi_tag and the pointlike tag. Often behaviour can be shared |
| between different geometry types. A tag, found by the metafunction tag, |
| can be casted to a more basic tag, and then dispatched by that tag. |
| \ingroup core |
| \tparam Tag The tag to be casted to one of the base tags |
| \tparam BaseTag First base tag |
| \tparam BaseTag2 Optional second base tag |
| \tparam BaseTag3 Optional third base tag |
| \tparam BaseTag4 Optional fourth base tag |
| \tparam BaseTag5 Optional fifth base tag |
| \tparam BaseTag6 Optional sixth base tag |
| \tparam BaseTag7 Optional seventh base tag |
| |
| \qbk{[include reference/core/tag_cast.qbk]} |
| */ |
| template |
| < |
| typename Tag, |
| typename BaseTag, |
| typename BaseTag2 = void, |
| typename BaseTag3 = void, |
| typename BaseTag4 = void, |
| typename BaseTag5 = void, |
| typename BaseTag6 = void, |
| typename BaseTag7 = void |
| > |
| struct tag_cast |
| { |
| typedef typename boost::mpl::if_ |
| < |
| typename boost::is_base_of<BaseTag, Tag>::type, |
| BaseTag, |
| // Try next one in line: |
| typename tag_cast |
| < |
| Tag, BaseTag2, BaseTag3, BaseTag4, |
| BaseTag5, BaseTag6, BaseTag7, void |
| >::type |
| >::type type; |
| }; |
| |
| #ifndef DOXYGEN_NO_SPECIALIZATIONS |
| |
| // Specialization for last one |
| template <typename Tag> |
| struct tag_cast<Tag, void, void, void, void, void, void, void> |
| { |
| // If not found, take specified tag, so do not cast |
| typedef Tag type; |
| }; |
| |
| #endif // DOXYGEN_NO_SPECIALIZATIONS |
| |
| |
| }} // namespace boost::geometry |
| |
| #endif // BOOST_GEOMETRY_CORE_TAG_CAST_HPP |