ceph/src/boost/boost/fusion/container/list/detail/at_impl.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_AT_IMPL_07172005_0726)
   8 #define FUSION_AT_IMPL_07172005_0726
   9
  10 #include <boost/fusion/support/config.hpp>
  11 #include <boost/fusion/support/detail/access.hpp>
  12 #include <boost/type_traits/is_const.hpp>
  13 #include <boost/type_traits/add_const.hpp>
  14 #include <boost/mpl/if.hpp>
  15 #include <boost/mpl/bool.hpp>
  16
  17 namespace boost { namespace fusion
  18 {
  19     namespace detail
  20     {
  21         template <typename Cons>
  22         struct cons_deref
  23         {
  24             typedef typename Cons::car_type type;
  25         };
  26
  27         template <typename Cons, int I>
  28         struct cons_advance
  29         {
  30             typedef typename
  31                 cons_advance<Cons, I-1>::type::cdr_type
  32             type;
  33         };
  34
  35         template <typename Cons>
  36         struct cons_advance<Cons, 0>
  37         {
  38             typedef Cons type;
  39         };
  40
  41         template <typename Cons>
  42         struct cons_advance<Cons, 1>
  43         {
  44             typedef typename Cons::cdr_type type;
  45         };
  46
  47         template <typename Cons>
  48         struct cons_advance<Cons, 2>
  49         {
  50 #if BOOST_WORKAROUND(BOOST_MSVC, > 1400) // VC8 and above
  51             typedef typename Cons::cdr_type::cdr_type type;
  52 #else
  53             typedef typename Cons::cdr_type _a;
  54             typedef typename _a::cdr_type type;
  55 #endif
  56         };
  57
  58         template <typename Cons>
  59         struct cons_advance<Cons, 3>
  60         {
  61 #if BOOST_WORKAROUND(BOOST_MSVC, > 1400) // VC8 and above
  62             typedef typename Cons::cdr_type::cdr_type::cdr_type type;
  63 #else
  64             typedef typename Cons::cdr_type _a;
  65             typedef typename _a::cdr_type _b;
  66             typedef typename _b::cdr_type type;
  67 #endif
  68         };
  69
  70         template <typename Cons>
  71         struct cons_advance<Cons, 4>
  72         {
  73 #if BOOST_WORKAROUND(BOOST_MSVC, > 1400) // VC8 and above
  74             typedef typename Cons::cdr_type::cdr_type::cdr_type::cdr_type type;
  75 #else
  76             typedef typename Cons::cdr_type _a;
  77             typedef typename _a::cdr_type _b;
  78             typedef typename _b::cdr_type _c;
  79             typedef typename _c::cdr_type type;
  80 #endif
  81         };
  82     }
  83
  84     struct cons_tag;
  85
  86     namespace extension
  87     {
  88         template <typename Tag>
  89         struct at_impl;
  90
  91         template <>
  92         struct at_impl<cons_tag>
  93         {
  94             template <typename Sequence, typename N>
  95             struct apply
  96             {
  97                 typedef typename detail::cons_deref<
  98                     typename detail::cons_advance<Sequence, N::value>::type>::type
  99                 element;
 100
 101                 typedef typename
 102                     mpl::if_<
 103                         is_const<Sequence>
 104                       , typename detail::cref_result<element>::type
 105                       , typename detail::ref_result<element>::type
 106                     >::type
 107                 type;
 108
 109                 template <typename Cons, int N2>
 110                 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
 111                 static type
 112                 call(Cons& s, mpl::int_<N2>)
 113                 {
 114                     return call(s.cdr, mpl::int_<N2-1>());
 115                 }
 116
 117                 template <typename Cons>
 118                 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
 119                 static type
 120                 call(Cons& s, mpl::int_<0>)
 121                 {
 122                     return s.car;
 123                 }
 124
 125                 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
 126                 static type
 127                 call(Sequence& s)
 128                 {
 129                     return call(s, mpl::int_<N::value>());
 130                 }
 131             };
 132         };
 133     }
 134 }}
 135
 136 #endif