ceph/src/boost/boost/fusion/sequence/intrinsic/value_at.hpp

   1 /*=============================================================================
   2     Copyright (c) 2001-2011 Joel de Guzman
   3
   4     Distributed under the Boost Software License, Version 1.0. (See accompanying
   5     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   6 ==============================================================================*/
   7 #if !defined(FUSION_VALUE_AT_05052005_0229)
   8 #define FUSION_VALUE_AT_05052005_0229
   9
  10 #include <boost/fusion/support/config.hpp>
  11 #include <boost/mpl/int.hpp>
  12 #include <boost/mpl/if.hpp>
  13 #include <boost/mpl/or.hpp>
  14 #include <boost/mpl/less.hpp>
  15 #include <boost/mpl/empty_base.hpp>
  16 #include <boost/fusion/sequence/intrinsic_fwd.hpp>
  17 #include <boost/fusion/support/tag_of.hpp>
  18 #include <boost/fusion/support/category_of.hpp>
  19
  20 namespace boost { namespace fusion
  21 {
  22     // Special tags:
  23     struct sequence_facade_tag;
  24     struct boost_tuple_tag; // boost::tuples::tuple tag
  25     struct boost_array_tag; // boost::array tag
  26     struct mpl_sequence_tag; // mpl sequence tag
  27     struct std_pair_tag; // std::pair tag
  28
  29     namespace extension
  30     {
  31         template <typename Tag>
  32         struct value_at_impl
  33         {
  34             template <typename Sequence, typename N>
  35             struct apply;
  36         };
  37
  38         template <>
  39         struct value_at_impl<sequence_facade_tag>
  40         {
  41             template <typename Sequence, typename N>
  42             struct apply : Sequence::template value_at<Sequence, N> {};
  43         };
  44
  45         template <>
  46         struct value_at_impl<boost_tuple_tag>;
  47
  48         template <>
  49         struct value_at_impl<boost_array_tag>;
  50
  51         template <>
  52         struct value_at_impl<mpl_sequence_tag>;
  53
  54         template <>
  55         struct value_at_impl<std_pair_tag>;
  56     }
  57
  58     namespace detail
  59     {
  60         template <typename Sequence, typename N, typename Tag>
  61         struct value_at_impl
  62             : mpl::if_<
  63                   mpl::or_<
  64                       mpl::less<N, typename extension::size_impl<Tag>::template apply<Sequence>::type>
  65                     , traits::is_unbounded<Sequence>
  66                   >
  67                 , typename extension::value_at_impl<Tag>::template apply<Sequence, N>
  68                 , mpl::empty_base
  69               >::type
  70         {};
  71     }
  72
  73     namespace result_of
  74     {
  75         template <typename Sequence, typename N>
  76         struct value_at
  77             : detail::value_at_impl<Sequence, N, typename detail::tag_of<Sequence>::type>
  78         {};
  79
  80         template <typename Sequence, int N>
  81         struct value_at_c
  82             : fusion::result_of::value_at<Sequence, mpl::int_<N> >
  83         {};
  84     }
  85 }}
  86
  87 #endif
  88