1/*=============================================================================
2 Copyright (c) 2001-2011 Joel de Guzman
3 Copyright (c) 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_AT_KEY_20060304_1755)
9#define BOOST_FUSION_AT_KEY_20060304_1755
10
11#include <boost/fusion/support/config.hpp>
12#include <boost/type_traits/is_const.hpp>
13#include <boost/fusion/sequence/intrinsic_fwd.hpp>
14#include <boost/fusion/sequence/intrinsic/has_key.hpp>
15#include <boost/fusion/algorithm/query/find.hpp>
16#include <boost/fusion/iterator/deref_data.hpp>
17#include <boost/fusion/support/tag_of.hpp>
18#include <boost/fusion/support/category_of.hpp>
19#include <boost/fusion/support/detail/access.hpp>
20#include <boost/mpl/empty_base.hpp>
21#include <boost/mpl/if.hpp>
22#include <boost/mpl/or.hpp>
23
24namespace boost { namespace fusion
25{
26 // Special tags:
27 struct sequence_facade_tag;
28 struct boost_array_tag; // boost::array tag
29 struct mpl_sequence_tag; // mpl sequence tag
30 struct std_pair_tag; // std::pair tag
31
32 namespace extension
33 {
34 template <typename Tag>
35 struct at_key_impl
36 {
37 template <typename Seq, typename Key>
38 struct apply
39 {
40 typedef typename
41 result_of::deref_data<
42 typename result_of::find<Seq, Key>::type
43 >::type
44 type;
45
46 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
47 static type
48 call(Seq& seq)
49 {
50 return fusion::deref_data(fusion::find<Key>(seq));
51 }
52 };
53 };
54
55 template <>
56 struct at_key_impl<sequence_facade_tag>
57 {
58 template <typename Sequence, typename Key>
59 struct apply : Sequence::template at_key_impl<Sequence, Key> {};
60 };
61
62 template <>
63 struct at_key_impl<boost_array_tag>;
64
65 template <>
66 struct at_key_impl<mpl_sequence_tag>;
67
68 template <>
69 struct at_key_impl<std_pair_tag>;
70 }
71
72 namespace detail
73 {
74 template <typename Sequence, typename Key, typename Tag>
75 struct at_key_impl
76 : mpl::if_<
77 mpl::or_<
78 typename extension::has_key_impl<Tag>::template apply<Sequence, Key>
79 , traits::is_unbounded<Sequence>
80 >
81 , typename extension::at_key_impl<Tag>::template apply<Sequence, Key>
82 , mpl::empty_base
83 >::type
84 {};
85 }
86
87 namespace result_of
88 {
89 template <typename Sequence, typename Key>
90 struct at_key
91 : detail::at_key_impl<Sequence, Key, typename detail::tag_of<Sequence>::type>
92 {};
93 }
94
95 template <typename Key, typename Sequence>
96 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
97 inline typename
98 lazy_disable_if<
99 is_const<Sequence>
100 , result_of::at_key<Sequence, Key>
101 >::type
102 at_key(Sequence& seq)
103 {
104 return result_of::at_key<Sequence, Key>::call(seq);
105 }
106
107 template <typename Key, typename Sequence>
108 BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
109 inline typename result_of::at_key<Sequence const, Key>::type
110 at_key(Sequence const& seq)
111 {
112 return result_of::at_key<Sequence const, Key>::call(seq);
113 }
114}}
115
116#endif
117