1 /*=============================================================================
2 Copyright (c) 2001-2011 Joel de Guzman
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_05042005_0722)
8 #define FUSION_AT_05042005_0722
10 #include <boost/fusion/support/config.hpp>
11 #include <boost/mpl/int.hpp>
12 #include <boost/mpl/if.hpp>
13 #include <boost/mpl/or.hpp>
14 #include <boost/mpl/less.hpp>
15 #include <boost/mpl/empty_base.hpp>
16 #include <boost/type_traits/is_const.hpp>
17 #include <boost/fusion/sequence/intrinsic_fwd.hpp>
18 #include <boost/fusion/support/tag_of.hpp>
19 #include <boost/fusion/support/category_of.hpp>
21 namespace boost { namespace fusion
24 struct sequence_facade_tag;
25 struct boost_tuple_tag; // boost::tuples::tuple tag
26 struct boost_array_tag; // boost::array tag
27 struct mpl_sequence_tag; // mpl sequence tag
28 struct std_pair_tag; // std::pair tag
29 struct std_tuple_tag; // std::tuple tag
33 template <typename Tag>
36 template <typename Sequence, typename N>
41 struct at_impl<sequence_facade_tag>
43 template <typename Sequence, typename N>
44 struct apply : Sequence::template at<Sequence, N> {};
48 struct at_impl<boost_tuple_tag>;
51 struct at_impl<boost_array_tag>;
54 struct at_impl<mpl_sequence_tag>;
57 struct at_impl<std_pair_tag>;
60 struct at_impl<std_tuple_tag>;
65 template <typename Sequence, typename N, typename Tag>
69 mpl::less<N, typename extension::size_impl<Tag>::template apply<Sequence>::type>
70 , traits::is_unbounded<Sequence>
72 , typename extension::at_impl<Tag>::template apply<Sequence, N>
80 template <typename Sequence, typename N>
82 : detail::at_impl<Sequence, N, typename detail::tag_of<Sequence>::type>
85 template <typename Sequence, int N>
87 : at<Sequence, mpl::int_<N> >
92 template <typename N, typename Sequence>
93 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
97 , result_of::at<Sequence, N>
101 return result_of::at<Sequence, N>::call(seq);
104 template <typename N, typename Sequence>
105 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
106 inline typename result_of::at<Sequence const, N>::type
107 at(Sequence const& seq)
109 return result_of::at<Sequence const, N>::call(seq);
112 template <int N, typename Sequence>
113 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
117 , result_of::at_c<Sequence, N>
121 return fusion::at<mpl::int_<N> >(seq);
124 template <int N, typename Sequence>
125 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
126 inline typename result_of::at_c<Sequence const, N>::type
127 at_c(Sequence const& seq)
129 return fusion::at<mpl::int_<N> >(seq);