| /*============================================================================= |
| 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_AT_IMPL_20060124_1933) |
| #define FUSION_AT_IMPL_20060124_1933 |
| |
| #include <boost/fusion/container/vector.hpp> |
| #include <boost/fusion/sequence/intrinsic/at.hpp> |
| #include <boost/fusion/container/vector/convert.hpp> |
| #include <boost/fusion/algorithm/transformation/transform.hpp> |
| #include <boost/type_traits/remove_reference.hpp> |
| #include <boost/type_traits/is_reference.hpp> |
| #include <boost/mpl/assert.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_at |
| { |
| template<typename T> |
| struct result; |
| |
| template<typename N1, typename SeqRef> |
| struct result<poly_at<N1>(SeqRef)> |
| : mpl::eval_if<is_same<SeqRef, unused_type const&>, |
| mpl::identity<unused_type>, |
| result_of::at<typename remove_reference<SeqRef>::type, N> > |
| { |
| BOOST_MPL_ASSERT((is_reference<SeqRef>)); |
| }; |
| |
| template<typename Seq> |
| typename result<poly_at(Seq&)>::type |
| operator()(Seq& seq) const |
| { |
| return fusion::at<N>(seq); |
| } |
| |
| template<typename Seq> |
| typename result<poly_at(Seq const&)>::type |
| operator()(Seq const& seq) const |
| { |
| return fusion::at<N>(seq); |
| } |
| |
| unused_type operator()(unused_type const&) const |
| { |
| return unused_type(); |
| } |
| }; |
| } |
| |
| namespace extension |
| { |
| template<typename Tag> |
| struct at_impl; |
| |
| template<> |
| struct at_impl<zip_view_tag> |
| { |
| template<typename Seq, typename N> |
| struct apply |
| { |
| typedef typename result_of::as_vector< |
| typename result_of::transform< |
| typename Seq::sequences, detail::poly_at<N> >::type>::type type; |
| |
| static type |
| call(Seq& seq) |
| { |
| return type( |
| fusion::transform(seq.sequences_, detail::poly_at<N>())); |
| } |
| }; |
| }; |
| } |
| }} |
| |
| #endif |