3rdparty/boost/boost/fusion/container/deque/detail/value_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_VALUE_AT_IMPL_08122006_0756)
   9 #define BOOST_FUSION_DEQUE_VALUE_AT_IMPL_08122006_0756
  10
  11 #include <boost/fusion/support/config.hpp>
  12 #include <boost/fusion/container/deque/detail/keyed_element.hpp>
  13
  14 #include <boost/mpl/equal_to.hpp>
  15 #include <boost/mpl/assert.hpp>
  16
  17 namespace boost { namespace fusion
  18 {
  19     struct deque_tag;
  20
  21     namespace extension
  22     {
  23         template<typename T>
  24         struct value_at_impl;
  25
  26         template<>
  27         struct value_at_impl<deque_tag>
  28         {
  29             template<typename Sequence, typename N>
  30             struct apply
  31             {
  32                 typedef typename Sequence::next_up next_up;
  33                 typedef typename Sequence::next_down next_down;
  34                 BOOST_MPL_ASSERT_RELATION(next_down::value, !=, next_up::value);
  35
  36                 static int const offset = next_down::value + 1;
  37                 typedef mpl::int_<(N::value + offset)> adjusted_index;
  38                 typedef typename
  39                     detail::keyed_element_value_at<Sequence, adjusted_index>::type
  40                 type;
  41             };
  42         };
  43     }
  44 }}
  45
  46 #endif