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/*=============================================================================
Copyright (c) 2001-2011 Joel de Guzman
Copyright (c) 2006 Dan Marsden
Distributed under 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)
==============================================================================*/
#if !defined(BOOST_FUSION_AT_KEY_20060304_1755)
#define BOOST_FUSION_AT_KEY_20060304_1755
#include <boost/type_traits/is_const.hpp>
#include <boost/fusion/sequence/intrinsic_fwd.hpp>
#include <boost/fusion/algorithm/query/find.hpp>
#include <boost/fusion/iterator/deref_data.hpp>
#include <boost/fusion/support/tag_of.hpp>
#include <boost/fusion/support/detail/access.hpp>
namespace boost { namespace fusion
{
// Special tags:
struct sequence_facade_tag;
struct boost_array_tag; // boost::array tag
struct mpl_sequence_tag; // mpl sequence tag
struct std_pair_tag; // std::pair tag
namespace extension
{
template <typename Tag>
struct at_key_impl
{
template <typename Seq, typename Key>
struct apply
{
typedef typename
result_of::deref_data<
typename result_of::find<Seq, Key>::type
>::type
type;
static type
call(Seq& seq)
{
return fusion::deref_data(fusion::find<Key>(seq));
}
};
};
template <>
struct at_key_impl<sequence_facade_tag>
{
template <typename Sequence, typename Key>
struct apply : Sequence::template at_key_impl<Sequence, Key> {};
};
template <>
struct at_key_impl<boost_array_tag>;
template <>
struct at_key_impl<mpl_sequence_tag>;
template <>
struct at_key_impl<std_pair_tag>;
}
namespace result_of
{
template <typename Sequence, typename Key>
struct at_key
: extension::at_key_impl<typename detail::tag_of<Sequence>::type>::
template apply<Sequence, Key>
{};
}
template <typename Key, typename Sequence>
inline typename
lazy_disable_if<
is_const<Sequence>
, result_of::at_key<Sequence, Key>
>::type
at_key(Sequence& seq)
{
return result_of::at_key<Sequence, Key>::call(seq);
}
template <typename Key, typename Sequence>
inline typename result_of::at_key<Sequence const, Key>::type
at_key(Sequence const& seq)
{
return result_of::at_key<Sequence const, Key>::call(seq);
}
}}
#endif
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Swift