| /*============================================================================= |
| 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 |