1 /*=============================================================================
2     Copyright (c) 2001-2011 Joel de Guzman
3 
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_HAS_KEY_09232005_1454)
8 #define FUSION_HAS_KEY_09232005_1454
9 
10 #include <boost/fusion/support/config.hpp>
11 #include <boost/fusion/sequence/intrinsic_fwd.hpp>
12 #include <boost/fusion/support/tag_of.hpp>
13 #include <boost/fusion/iterator/equal_to.hpp>
14 #include <boost/fusion/algorithm/query/find.hpp>
15 #include <boost/fusion/sequence/intrinsic/end.hpp>
16 #include <boost/mpl/not.hpp>
17 
18 namespace boost { namespace fusion
19 {
20     struct void_;
21 
22     // Special tags:
23     struct sequence_facade_tag;
24     struct boost_array_tag; // boost::array tag
25     struct mpl_sequence_tag; // mpl sequence tag
26     struct std_pair_tag; // std::pair tag
27 
28     namespace extension
29     {
30         template <typename Tag>
31         struct has_key_impl
32         {
33             template <typename Seq, typename Key>
34             struct apply
35               : mpl::not_<
36                     typename result_of::equal_to<
37                         typename result_of::find<Seq, Key>::type
38                       , typename result_of::end<Seq>::type
39                     >::type
40                 >::type
41             {};
42         };
43 
44         template <>
45         struct has_key_impl<sequence_facade_tag>
46         {
47             template <typename Sequence, typename Key>
48             struct apply : Sequence::template has_key<Sequence, Key> {};
49         };
50 
51         template <>
52         struct has_key_impl<boost_array_tag>;
53 
54         template <>
55         struct has_key_impl<mpl_sequence_tag>;
56 
57         template <>
58         struct has_key_impl<std_pair_tag>;
59     }
60 
61     namespace result_of
62     {
63         template <typename Sequence, typename Key>
64         struct has_key
65             : extension::has_key_impl<typename detail::tag_of<Sequence>::type>::
66                 template apply<Sequence, Key>
67         {};
68     }
69 
70     template <typename Key, typename Sequence>
71     BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
72     inline typename result_of::has_key<Sequence, Key>::type
has_key(Sequence const &)73     has_key(Sequence const&)
74     {
75         typedef typename result_of::has_key<Sequence, Key>::type result;
76         return result();
77     }
78 }}
79 
80 #endif
81 
82