1/* Copyright 2003-2013 Joaquin M Lopez Munoz.
2 * Distributed under the Boost Software License, Version 1.0.
3 * (See accompanying file LICENSE_1_0.txt or copy at
4 * http://www.boost.org/LICENSE_1_0.txt)
5 *
6 * See http://www.boost.org/libs/multi_index for library home page.
7 */
8
9#ifndef BOOST_MULTI_INDEX_DETAIL_NO_DUPLICATE_TAGS_HPP
10#define BOOST_MULTI_INDEX_DETAIL_NO_DUPLICATE_TAGS_HPP
11
12#if defined(_MSC_VER)
13#pragma once
14#endif
15
16#include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */
17#include <boost/mpl/fold.hpp>
18#include <boost/mpl/set/set0.hpp>
19
20namespace boost{
21
22namespace multi_index{
23
24namespace detail{
25
26/* no_duplicate_tags check at compile-time that a tag list
27 * has no duplicate tags.
28 * The algorithm deserves some explanation: tags
29 * are sequentially inserted into a mpl::set if they were
30 * not already present. Due to the magic of mpl::set
31 * (mpl::has_key is contant time), this operation takes linear
32 * time, and even MSVC++ 6.5 handles it gracefully (other obvious
33 * solutions are quadratic.)
34 */
35
36struct duplicate_tag_mark{};
37
38struct duplicate_tag_marker
39{
40 template <typename MplSet,typename Tag>
41 struct apply
42 {
43 typedef mpl::s_item<
44 typename mpl::if_<mpl::has_key<MplSet,Tag>,duplicate_tag_mark,Tag>::type,
45 MplSet
46 > type;
47 };
48};
49
50template<typename TagList>
51struct no_duplicate_tags
52{
53 typedef typename mpl::fold<
54 TagList,
55 mpl::set0<>,
56 duplicate_tag_marker
57 >::type aux;
58
59 BOOST_STATIC_CONSTANT(
60 bool,value=!(mpl::has_key<aux,duplicate_tag_mark>::value));
61};
62
63/* Variant for an index list: duplication is checked
64 * across all the indices.
65 */
66
67struct duplicate_tag_list_marker
68{
69 template <typename MplSet,typename Index>
70 struct apply:mpl::fold<
71 BOOST_DEDUCED_TYPENAME Index::tag_list,
72 MplSet,
73 duplicate_tag_marker>
74 {
75 };
76};
77
78template<typename IndexList>
79struct no_duplicate_tags_in_index_list
80{
81 typedef typename mpl::fold<
82 IndexList,
83 mpl::set0<>,
84 duplicate_tag_list_marker
85 >::type aux;
86
87 BOOST_STATIC_CONSTANT(
88 bool,value=!(mpl::has_key<aux,duplicate_tag_mark>::value));
89};
90
91} /* namespace multi_index::detail */
92
93} /* namespace multi_index */
94
95} /* namespace boost */
96
97#endif
98

source code of boost/boost/multi_index/detail/no_duplicate_tags.hpp