3rdparty/boost/boost/fusion/container/deque/detail/at_impl.hpp

   1 /*=============================================================================
   2     Copyright (c) 2005-2012 Joel de Guzman
   3     Copyright (c) 2005-2006 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_DEQUE_AT_IMPL_09122006_2017)
   9 #define BOOST_FUSION_DEQUE_AT_IMPL_09122006_2017
  10
  11 #include <boost/fusion/support/config.hpp>
  12 #include <boost/fusion/container/deque/detail/keyed_element.hpp>
  13
  14 #include <boost/mpl/eval_if.hpp>
  15 #include <boost/mpl/equal_to.hpp>
  16 #include <boost/mpl/assert.hpp>
  17 #include <boost/mpl/identity.hpp>
  18
  19 #include <boost/type_traits/is_const.hpp>
  20 #include <boost/type_traits/add_const.hpp>
  21 #include <boost/type_traits/add_reference.hpp>
  22
  23 namespace boost { namespace fusion
  24 {
  25     struct deque_tag;
  26
  27     namespace extension
  28     {
  29         template<typename T>
  30         struct at_impl;
  31
  32         template<>
  33         struct at_impl<deque_tag>
  34         {
  35             template<typename Sequence, typename N>
  36             struct apply
  37             {
  38                 typedef typename Sequence::next_up next_up;
  39                 typedef typename Sequence::next_down next_down;
  40                 BOOST_MPL_ASSERT_RELATION(next_down::value, !=, next_up::value);
  41
  42                 static int const offset = next_down::value + 1;
  43                 typedef mpl::int_<(N::value + offset)> adjusted_index;
  44                 typedef typename
  45                     detail::keyed_element_value_at<Sequence, adjusted_index>::type
  46                 element_type;
  47
  48                 typedef typename
  49                     add_reference<
  50                       typename mpl::eval_if<
  51                       is_const<Sequence>,
  52                       add_const<element_type>,
  53                       mpl::identity<element_type> >::type
  54                     >::type
  55                 type;
  56
  57                 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
  58                 static type call(Sequence& seq)
  59                 {
  60                     return seq.get(adjusted_index());
  61                 }
  62             };
  63         };
  64     }
  65 }}
  66
  67 #endif