Chris@16: /*=============================================================================
Chris@16:     Copyright (c) 2005-2012 Joel de Guzman
Chris@16:     Copyright (c) 2005-2006 Dan Marsden
Chris@16: 
Chris@16:     Distributed under the Boost Software License, Version 1.0. (See accompanying
Chris@16:     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
Chris@16: ==============================================================================*/
Chris@16: #if !defined(BOOST_FUSION_DEQUE_AT_IMPL_09122006_2017)
Chris@16: #define BOOST_FUSION_DEQUE_AT_IMPL_09122006_2017
Chris@16: 
Chris@101: #include <boost/fusion/support/config.hpp>
Chris@16: #include <boost/fusion/container/deque/detail/keyed_element.hpp>
Chris@16: 
Chris@16: #include <boost/mpl/eval_if.hpp>
Chris@16: #include <boost/mpl/equal_to.hpp>
Chris@16: #include <boost/mpl/assert.hpp>
Chris@16: #include <boost/mpl/identity.hpp>
Chris@16: 
Chris@16: #include <boost/type_traits/is_const.hpp>
Chris@16: #include <boost/type_traits/add_const.hpp>
Chris@16: #include <boost/type_traits/add_reference.hpp>
Chris@16: 
Chris@16: namespace boost { namespace fusion
Chris@16: {
Chris@16:     struct deque_tag;
Chris@16: 
Chris@16:     namespace extension
Chris@16:     {
Chris@16:         template<typename T>
Chris@16:         struct at_impl;
Chris@16: 
Chris@16:         template<>
Chris@16:         struct at_impl<deque_tag>
Chris@16:         {
Chris@16:             template<typename Sequence, typename N>
Chris@16:             struct apply
Chris@16:             {
Chris@16:                 typedef typename Sequence::next_up next_up;
Chris@16:                 typedef typename Sequence::next_down next_down;
Chris@16:                 BOOST_MPL_ASSERT_RELATION(next_down::value, !=, next_up::value);
Chris@16: 
Chris@16:                 static int const offset = next_down::value + 1;
Chris@16:                 typedef mpl::int_<(N::value + offset)> adjusted_index;
Chris@16:                 typedef typename
Chris@16:                     detail::keyed_element_value_at<Sequence, adjusted_index>::type
Chris@16:                 element_type;
Chris@16: 
Chris@16:                 typedef typename
Chris@16:                     add_reference<
Chris@16:                       typename mpl::eval_if<
Chris@16:                       is_const<Sequence>,
Chris@16:                       add_const<element_type>,
Chris@16:                       mpl::identity<element_type> >::type
Chris@16:                     >::type
Chris@16:                 type;
Chris@16: 
Chris@101:                 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
Chris@16:                 static type call(Sequence& seq)
Chris@16:                 {
Chris@16:                     return seq.get(adjusted_index());
Chris@16:                 }
Chris@16:             };
Chris@16:         };
Chris@16:     }
Chris@16: }}
Chris@16: 
Chris@16: #endif