Chris@102: // Boost.Geometry (aka GGL, Generic Geometry Library)
Chris@102: 
Chris@102: // Copyright (c) 2007-2015 Barend Gehrels, Amsterdam, the Netherlands.
Chris@102: // Copyright (c) 2008-2015 Bruno Lalande, Paris, France.
Chris@102: // Copyright (c) 2009-2015 Mateusz Loskot, London, UK.
Chris@102: 
Chris@102: // This file was modified by Oracle on 2015.
Chris@102: // Modifications copyright (c) 2015, Oracle and/or its affiliates.
Chris@102: 
Chris@102: // Contributed and/or modified by Menelaos Karavelas, on behalf of Oracle
Chris@102: 
Chris@102: // Parts of Boost.Geometry are redesigned from Geodan's Geographic Library
Chris@102: // (geolib/GGL), copyright (c) 1995-2010 Geodan, Amsterdam, the Netherlands.
Chris@102: 
Chris@102: // Use, modification and distribution is subject to the Boost Software License,
Chris@102: // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
Chris@102: // http://www.boost.org/LICENSE_1_0.txt)
Chris@102: 
Chris@102: #ifndef BOOST_GEOMETRY_UTIL_COMPRESS_VARIANT_HPP
Chris@102: #define BOOST_GEOMETRY_UTIL_COMPRESS_VARIANT_HPP
Chris@102: 
Chris@102: 
Chris@102: #include <boost/mpl/equal_to.hpp>
Chris@102: #include <boost/mpl/fold.hpp>
Chris@102: #include <boost/mpl/front.hpp>
Chris@102: #include <boost/mpl/if.hpp>
Chris@102: #include <boost/mpl/insert.hpp>
Chris@102: #include <boost/mpl/int.hpp>
Chris@102: #include <boost/mpl/set.hpp>
Chris@102: #include <boost/mpl/size.hpp>
Chris@102: #include <boost/mpl/vector.hpp>
Chris@102: #include <boost/variant/variant_fwd.hpp>
Chris@102: 
Chris@102: 
Chris@102: namespace boost { namespace geometry
Chris@102: {
Chris@102: 
Chris@102: 
Chris@102: namespace detail
Chris@102: {
Chris@102: 
Chris@102: template <typename Variant>
Chris@102: struct unique_types:
Chris@102:     boost::mpl::fold<
Chris@102:         typename boost::mpl::reverse_fold<
Chris@102:             typename Variant::types,
Chris@102:             boost::mpl::set<>,
Chris@102:             boost::mpl::insert<
Chris@102:                 boost::mpl::placeholders::_1,
Chris@102:                 boost::mpl::placeholders::_2
Chris@102:             >
Chris@102:         >::type,
Chris@102:         boost::mpl::vector<>,
Chris@102:         boost::mpl::push_back
Chris@102:             <
Chris@102:                 boost::mpl::placeholders::_1, boost::mpl::placeholders::_2
Chris@102:             >
Chris@102:     >
Chris@102: {};
Chris@102: 
Chris@102: template <typename Types>
Chris@102: struct variant_or_single:
Chris@102:     boost::mpl::if_<
Chris@102:         boost::mpl::equal_to<
Chris@102:             boost::mpl::size<Types>,
Chris@102:             boost::mpl::int_<1>
Chris@102:         >,
Chris@102:         typename boost::mpl::front<Types>::type,
Chris@102:         typename make_variant_over<Types>::type
Chris@102:     >
Chris@102: {};
Chris@102: 
Chris@102: } // namespace detail
Chris@102: 
Chris@102: 
Chris@102: /*!
Chris@102:     \brief Meta-function that takes a boost::variant type and tries to minimize
Chris@102:         it by doing the following:
Chris@102:         - if there's any duplicate types, remove them
Chris@102:         - if the result is a variant of one type, turn it into just that type
Chris@102:     \ingroup utility
Chris@102:     \par Example
Chris@102:     \code
Chris@102:         typedef variant<int, float, int, long> variant_type;
Chris@102:         typedef compress_variant<variant_type>::type compressed;
Chris@102:         typedef boost::mpl::vector<int, float, long> result_types;
Chris@102:         BOOST_MPL_ASSERT(( boost::mpl::equal<compressed::types, result_types> ));
Chris@102: 
Chris@102:         typedef variant<int, int, int> one_type_variant_type;
Chris@102:         typedef compress_variant<one_type_variant_type>::type single_type;
Chris@102:         BOOST_MPL_ASSERT(( boost::equals<single_type, int> ));
Chris@102:     \endcode
Chris@102: */
Chris@102: 
Chris@102: template <typename Variant>
Chris@102: struct compress_variant:
Chris@102:     detail::variant_or_single<
Chris@102:         typename detail::unique_types<Variant>::type
Chris@102:     >
Chris@102: {};
Chris@102: 
Chris@102: 
Chris@102: }} // namespace boost::geometry
Chris@102: 
Chris@102: 
Chris@102: #endif // BOOST_GEOMETRY_UTIL_COMPRESS_VARIANT_HPP