1
2#ifndef BOOST_MPL_SEQUENCE_TAG_HPP_INCLUDED
3#define BOOST_MPL_SEQUENCE_TAG_HPP_INCLUDED
4
5// Copyright Aleksey Gurtovoy 2000-2004
6//
7// Distributed under the Boost Software License, Version 1.0.
8// (See accompanying file LICENSE_1_0.txt or copy at
9// http://www.boost.org/LICENSE_1_0.txt)
10//
11// See http://www.boost.org/libs/mpl for documentation.
12
13// $Id$
14// $Date$
15// $Revision$
16
17#include <boost/mpl/sequence_tag_fwd.hpp>
18#include <boost/mpl/aux_/has_tag.hpp>
19#include <boost/mpl/aux_/has_begin.hpp>
20#include <boost/mpl/aux_/na_spec.hpp>
21#include <boost/mpl/aux_/is_msvc_eti_arg.hpp>
22#include <boost/mpl/aux_/config/eti.hpp>
23#include <boost/mpl/aux_/yes_no.hpp>
24#include <boost/mpl/aux_/config/workaround.hpp>
25
26namespace boost { namespace mpl {
27
28// agurt, 27/nov/02: have to use a simplistic 'sequence_tag' implementation
29// on MSVC to avoid dreadful "internal structure overflow" error
30#if BOOST_WORKAROUND(BOOST_MSVC, < 1300) \
31 || defined(BOOST_MPL_CFG_NO_HAS_XXX)
32
33template<
34 typename BOOST_MPL_AUX_NA_PARAM(Sequence)
35 >
36struct sequence_tag
37{
38 typedef typename Sequence::tag type;
39};
40
41#elif BOOST_WORKAROUND(BOOST_MSVC, == 1300)
42
43// agurt, 07/feb/03: workaround for what seems to be MSVC 7.0-specific ETI issue
44
45namespace aux {
46
47template< bool >
48struct sequence_tag_impl
49{
50 template< typename Sequence > struct result_
51 {
52 typedef typename Sequence::tag type;
53 };
54};
55
56template<>
57struct sequence_tag_impl<false>
58{
59 template< typename Sequence > struct result_
60 {
61 typedef int type;
62 };
63};
64
65} // namespace aux
66
67template<
68 typename BOOST_MPL_AUX_NA_PARAM(Sequence)
69 >
70struct sequence_tag
71 : aux::sequence_tag_impl< !aux::is_msvc_eti_arg<Sequence>::value >
72 ::template result_<Sequence>
73{
74};
75
76#else
77
78namespace aux {
79
80template< bool has_tag_, bool has_begin_ >
81struct sequence_tag_impl
82{
83 // agurt 24/nov/02: MSVC 6.5 gets confused in 'sequence_tag_impl<true>'
84 // specialization below, if we name it 'result_' here
85 template< typename Sequence > struct result2_;
86};
87
88# define AUX_CLASS_SEQUENCE_TAG_SPEC(has_tag, has_begin, result_type) \
89template<> struct sequence_tag_impl<has_tag,has_begin> \
90{ \
91 template< typename Sequence > struct result2_ \
92 { \
93 typedef result_type type; \
94 }; \
95}; \
96/**/
97
98AUX_CLASS_SEQUENCE_TAG_SPEC(true, true, typename Sequence::tag)
99AUX_CLASS_SEQUENCE_TAG_SPEC(true, false, typename Sequence::tag)
100AUX_CLASS_SEQUENCE_TAG_SPEC(false, true, nested_begin_end_tag)
101AUX_CLASS_SEQUENCE_TAG_SPEC(false, false, non_sequence_tag)
102
103# undef AUX_CLASS_SEQUENCE_TAG_SPEC
104
105} // namespace aux
106
107template<
108 typename BOOST_MPL_AUX_NA_PARAM(Sequence)
109 >
110struct sequence_tag
111 : aux::sequence_tag_impl<
112 ::boost::mpl::aux::has_tag<Sequence>::value
113 , ::boost::mpl::aux::has_begin<Sequence>::value
114 >::template result2_<Sequence>
115{
116};
117
118#endif // BOOST_MSVC
119
120BOOST_MPL_AUX_NA_SPEC(1, sequence_tag)
121
122}}
123
124#endif // BOOST_MPL_SEQUENCE_TAG_HPP_INCLUDED
125

source code of boost/boost/mpl/sequence_tag.hpp