ceph/src/boost/libs/fusion/include/boost/fusion/sequence/intrinsic/at_key.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(BOOST_FUSION_AT_KEY_20060304_1755)
   9 #define BOOST_FUSION_AT_KEY_20060304_1755
  10
  11 #include <boost/fusion/support/config.hpp>
  12 #include <boost/type_traits/is_const.hpp>
  13 #include <boost/fusion/sequence/intrinsic_fwd.hpp>
  14 #include <boost/fusion/sequence/intrinsic/has_key.hpp>
  15 #include <boost/fusion/algorithm/query/find.hpp>
  16 #include <boost/fusion/iterator/deref_data.hpp>
  17 #include <boost/fusion/support/tag_of.hpp>
  18 #include <boost/fusion/support/category_of.hpp>
  19 #include <boost/fusion/support/detail/access.hpp>
  20 #include <boost/mpl/empty_base.hpp>
  21 #include <boost/mpl/if.hpp>
  22 #include <boost/mpl/or.hpp>
  23
  24 namespace boost { namespace fusion
  25 {
  26     // Special tags:
  27     struct sequence_facade_tag;
  28     struct boost_array_tag; // boost::array tag
  29     struct mpl_sequence_tag; // mpl sequence tag
  30     struct std_pair_tag; // std::pair tag
  31
  32     namespace extension
  33     {
  34         template <typename Tag>
  35         struct at_key_impl
  36         {
  37             template <typename Seq, typename Key>
  38             struct apply
  39             {
  40                 typedef typename
  41                     result_of::deref_data<
  42                         typename result_of::find<Seq, Key>::type
  43                     >::type
  44                 type;
  45
  46                 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
  47                 static type
  48                 call(Seq& seq)
  49                 {
  50                     return fusion::deref_data(fusion::find<Key>(seq));
  51                 }
  52             };
  53         };
  54
  55         template <>
  56         struct at_key_impl<sequence_facade_tag>
  57         {
  58             template <typename Sequence, typename Key>
  59             struct apply : Sequence::template at_key_impl<Sequence, Key> {};
  60         };
  61
  62         template <>
  63         struct at_key_impl<boost_array_tag>;
  64
  65         template <>
  66         struct at_key_impl<mpl_sequence_tag>;
  67
  68         template <>
  69         struct at_key_impl<std_pair_tag>;
  70     }
  71
  72     namespace detail
  73     {
  74         template <typename Sequence, typename Key, typename Tag>
  75         struct at_key_impl
  76             : mpl::if_<
  77                   mpl::or_<
  78                       typename extension::has_key_impl<Tag>::template apply<Sequence, Key>
  79                     , traits::is_unbounded<Sequence>
  80                   >
  81                 , typename extension::at_key_impl<Tag>::template apply<Sequence, Key>
  82                 , mpl::empty_base
  83               >::type
  84         {};
  85     }
  86
  87     namespace result_of
  88     {
  89         template <typename Sequence, typename Key>
  90         struct at_key
  91             : detail::at_key_impl<Sequence, Key, typename detail::tag_of<Sequence>::type>
  92         {};
  93     }
  94
  95     template <typename Key, typename Sequence>
  96     BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
  97     inline typename
  98         lazy_disable_if<
  99             is_const<Sequence>
 100           , result_of::at_key<Sequence, Key>
 101         >::type
 102     at_key(Sequence& seq)
 103     {
 104         return result_of::at_key<Sequence, Key>::call(seq);
 105     }
 106
 107     template <typename Key, typename Sequence>
 108     BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
 109     inline typename result_of::at_key<Sequence const, Key>::type
 110     at_key(Sequence const& seq)
 111     {
 112         return result_of::at_key<Sequence const, Key>::call(seq);
 113     }
 114 }}
 115
 116 #endif