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_TAG_OF_09232005_0845)
8#define FUSION_TAG_OF_09232005_0845
9
10#include <boost/fusion/support/config.hpp>
11#include <boost/utility/enable_if.hpp>
12#include <boost/type_traits/remove_const.hpp>
13#include <boost/fusion/support/tag_of_fwd.hpp>
14#include <boost/fusion/support/detail/is_mpl_sequence.hpp>
15#include <boost/mpl/has_xxx.hpp>
16#include <boost/mpl/identity.hpp>
17#include <boost/mpl/assert.hpp>
18#include <boost/mpl/bool.hpp>
19#include <boost/mpl/if.hpp>
20#include <boost/config/no_tr1/utility.hpp>
21
22namespace boost
23{
24 template <typename T, std::size_t N>
25 class array; // forward
26
27 namespace tuples
28 {
29 struct null_type;
30
31 template <
32 class T0, class T1, class T2, class T3, class T4,
33 class T5, class T6, class T7, class T8, class T9
34 >
35 class tuple;
36
37 template <class Head, class Tail>
38 struct cons;
39 }
40}
41
42namespace boost { namespace fusion
43{
44 struct non_fusion_tag;
45 struct mpl_sequence_tag;
46
47 namespace detail
48 {
49 BOOST_MPL_HAS_XXX_TRAIT_DEF(fusion_tag)
50
51 template <typename Sequence, typename Active>
52 struct tag_of_impl
53 : mpl::if_<fusion::detail::is_mpl_sequence<Sequence>,
54 mpl::identity<mpl_sequence_tag>,
55 mpl::identity<non_fusion_tag> >::type
56 {};
57
58 template <typename Sequence>
59 struct tag_of_impl<
60 Sequence
61 , typename boost::enable_if<detail::has_fusion_tag<Sequence> >::type>
62 {
63 typedef typename Sequence::fusion_tag type;
64 };
65 }
66
67 namespace traits
68 {
69 template <typename Sequence, typename Active>
70 struct tag_of
71 : boost::fusion::detail::tag_of_impl<Sequence, Active>
72 {};
73 }
74
75 namespace detail
76 {
77 template<typename T>
78 struct tag_of
79 : traits::tag_of<typename remove_const<T>::type>
80 {};
81 }
82}}
83#endif
84

source code of include/boost/fusion/support/tag_of.hpp