ceph/src/boost/boost/fusion/view/zip_view/detail/at_impl.hpp

   1 /*=============================================================================
   2     Copyright (c) 2001-2011 Joel de Guzman
   3     Copyright (c) 2006 Dan Marsden
   4
   5     Distributed under the Boost Software License, Version 1.0. (See accompanying
   6     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   7 ==============================================================================*/
   8 #if !defined(FUSION_AT_IMPL_20060124_1933)
   9 #define FUSION_AT_IMPL_20060124_1933
  10
  11 #include <boost/fusion/support/config.hpp>
  12 #include <boost/fusion/container/vector.hpp>
  13 #include <boost/fusion/sequence/intrinsic/at.hpp>
  14 #include <boost/fusion/container/vector/convert.hpp>
  15 #include <boost/fusion/algorithm/transformation/transform.hpp>
  16 #include <boost/type_traits/remove_reference.hpp>
  17 #include <boost/type_traits/is_reference.hpp>
  18 #include <boost/mpl/assert.hpp>
  19 #include <boost/fusion/support/unused.hpp>
  20 #include <boost/mpl/eval_if.hpp>
  21 #include <boost/mpl/identity.hpp>
  22 #include <boost/type_traits/is_same.hpp>
  23
  24
  25 namespace boost { namespace fusion
  26 {
  27     struct zip_view_tag;
  28
  29     namespace detail
  30     {
  31         template<typename N>
  32         struct poly_at
  33         {
  34             template<typename T>
  35             struct result;
  36
  37             template<typename N1, typename SeqRef>
  38             struct result<poly_at<N1>(SeqRef)>
  39                 : mpl::eval_if<is_same<SeqRef, unused_type const&>,
  40                                mpl::identity<unused_type>,
  41                                result_of::at<typename remove_reference<SeqRef>::type, N> >
  42             {
  43                 BOOST_MPL_ASSERT((is_reference<SeqRef>));
  44             };
  45
  46             template<typename Seq>
  47             BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
  48             typename result<poly_at(Seq&)>::type
  49             operator()(Seq& seq) const
  50             {
  51                 return fusion::at<N>(seq);
  52             }
  53
  54             template<typename Seq>
  55             BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
  56             typename result<poly_at(Seq const&)>::type
  57             operator()(Seq const& seq) const
  58             {
  59                 return fusion::at<N>(seq);
  60             }
  61
  62             BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
  63             unused_type operator()(unused_type const&) const
  64             {
  65                 return unused_type();
  66             }
  67         };
  68     }
  69
  70     namespace extension
  71     {
  72         template<typename Tag>
  73         struct at_impl;
  74
  75         template<>
  76         struct at_impl<zip_view_tag>
  77         {
  78             template<typename Seq, typename N>
  79             struct apply
  80             {
  81                 typedef typename result_of::as_vector<
  82                     typename result_of::transform<
  83                     typename Seq::sequences, detail::poly_at<N> >::type>::type type;
  84
  85                 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
  86                 static type
  87                 call(Seq& seq)
  88                 {
  89                     return type(
  90                         fusion::transform(seq.sequences_, detail::poly_at<N>()));
  91                 }
  92             };
  93         };
  94     }
  95 }}
  96
  97 #endif