99 lines
2.7 KiB
C++
99 lines
2.7 KiB
C++
// Boost.Geometry (aka GGL, Generic Geometry Library)
|
|
|
|
// Copyright (c) 2007-2012 Barend Gehrels, Amsterdam, the Netherlands.
|
|
// Copyright (c) 2008-2012 Bruno Lalande, Paris, France.
|
|
// Copyright (c) 2009-2012 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_UTIL_COMPRESS_VARIANT_HPP
|
|
#define BOOST_GEOMETRY_UTIL_COMPRESS_VARIANT_HPP
|
|
|
|
|
|
#include <boost/mpl/equal_to.hpp>
|
|
#include <boost/mpl/fold.hpp>
|
|
#include <boost/mpl/front.hpp>
|
|
#include <boost/mpl/if.hpp>
|
|
#include <boost/mpl/insert.hpp>
|
|
#include <boost/mpl/int.hpp>
|
|
#include <boost/mpl/set.hpp>
|
|
#include <boost/mpl/size.hpp>
|
|
#include <boost/mpl/vector.hpp>
|
|
#include <boost/variant/variant_fwd.hpp>
|
|
|
|
|
|
namespace boost { namespace geometry
|
|
{
|
|
|
|
|
|
namespace detail
|
|
{
|
|
|
|
template <typename Variant>
|
|
struct unique_types:
|
|
mpl::fold<
|
|
typename mpl::reverse_fold<
|
|
typename Variant::types,
|
|
mpl::set<>,
|
|
mpl::insert<
|
|
mpl::placeholders::_1,
|
|
mpl::placeholders::_2
|
|
>
|
|
>::type,
|
|
mpl::vector<>,
|
|
mpl::push_back<mpl::placeholders::_1, mpl::placeholders::_2>
|
|
>
|
|
{};
|
|
|
|
template <typename Types>
|
|
struct variant_or_single:
|
|
mpl::if_<
|
|
mpl::equal_to<
|
|
mpl::size<Types>,
|
|
mpl::int_<1>
|
|
>,
|
|
typename mpl::front<Types>::type,
|
|
typename make_variant_over<Types>::type
|
|
>
|
|
{};
|
|
|
|
} // namespace detail
|
|
|
|
|
|
/*!
|
|
\brief Meta-function that takes a boost::variant type and tries to minimize
|
|
it by doing the following:
|
|
- if there's any duplicate types, remove them
|
|
- if the result is a variant of one type, turn it into just that type
|
|
\ingroup utility
|
|
\par Example
|
|
\code
|
|
typedef variant<int, float, int, long> variant_type;
|
|
typedef compress_variant<variant_type>::type compressed;
|
|
typedef mpl::vector<int, float, long> result_types;
|
|
BOOST_MPL_ASSERT(( mpl::equal<compressed::types, result_types> ));
|
|
|
|
typedef variant<int, int, int> one_type_variant_type;
|
|
typedef compress_variant<one_type_variant_type>::type single_type;
|
|
BOOST_MPL_ASSERT(( boost::equals<single_type, int> ));
|
|
\endcode
|
|
*/
|
|
|
|
template <typename Variant>
|
|
struct compress_variant:
|
|
detail::variant_or_single<
|
|
typename detail::unique_types<Variant>::type
|
|
>
|
|
{};
|
|
|
|
|
|
}} // namespace boost::geometry
|
|
|
|
|
|
#endif // BOOST_GEOMETRY_UTIL_COMPRESS_VARIANT_HPP
|