/*============================================================================= | |
Copyright (c) 2001-2006 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(FUSION_VALUE_AT_IMPL_20060124_2129) | |
#define FUSION_VALUE_AT_IMPL_20060124_2129 | |
#include <boost/fusion/container/vector/convert.hpp> | |
#include <boost/fusion/algorithm/transformation/transform.hpp> | |
#include <boost/fusion/sequence/intrinsic/value_at.hpp> | |
#include <boost/type_traits/remove_reference.hpp> | |
#include <boost/fusion/support/unused.hpp> | |
#include <boost/mpl/eval_if.hpp> | |
#include <boost/mpl/identity.hpp> | |
#include <boost/type_traits/is_same.hpp> | |
namespace boost { namespace fusion { | |
struct zip_view_tag; | |
namespace detail | |
{ | |
template<typename N> | |
struct poly_value_at | |
{ | |
template<typename T> | |
struct result; | |
template<typename N1, typename Seq> | |
struct result<poly_value_at<N1>(Seq)> | |
: mpl::eval_if<is_same<Seq, unused_type const&>, | |
mpl::identity<unused_type>, | |
result_of::value_at<typename remove_reference<Seq>::type, N> > | |
{}; | |
}; | |
} | |
namespace extension | |
{ | |
template<typename Tag> | |
struct value_at_impl; | |
template<> | |
struct value_at_impl<zip_view_tag> | |
{ | |
template<typename Sequence, typename N> | |
struct apply | |
{ | |
typedef typename result_of::transform< | |
typename Sequence::sequences, | |
detail::poly_value_at<N> >::type values; | |
typedef typename result_of::as_vector<values>::type type; | |
}; | |
}; | |
} | |
}} | |
#endif |