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1 | // (C) Copyright Jeremy Siek 2002. |
2 | // Distributed under the Boost Software License, Version 1.0. (See | |
3 | // accompanying file LICENSE_1_0.txt or copy at | |
4 | // http://www.boost.org/LICENSE_1_0.txt) | |
5 | ||
6 | #ifndef BOOST_ITERATOR_CATEGORIES_HPP | |
7 | # define BOOST_ITERATOR_CATEGORIES_HPP | |
8 | ||
9 | # include <boost/config.hpp> | |
10 | # include <boost/detail/iterator.hpp> | |
11 | # include <boost/iterator/detail/config_def.hpp> | |
12 | ||
13 | # include <boost/detail/workaround.hpp> | |
14 | ||
15 | # include <boost/mpl/eval_if.hpp> | |
16 | # include <boost/mpl/identity.hpp> | |
17 | # include <boost/mpl/placeholders.hpp> | |
18 | # include <boost/mpl/aux_/lambda_support.hpp> | |
19 | ||
20 | # include <boost/type_traits/is_convertible.hpp> | |
21 | ||
22 | # include <boost/static_assert.hpp> | |
23 | ||
24 | namespace boost { | |
25 | namespace iterators { | |
26 | ||
27 | // | |
28 | // Traversal Categories | |
29 | // | |
30 | ||
31 | struct no_traversal_tag {}; | |
32 | ||
33 | struct incrementable_traversal_tag | |
34 | : no_traversal_tag | |
35 | { | |
36 | // incrementable_traversal_tag() {} | |
37 | // incrementable_traversal_tag(std::output_iterator_tag const&) {}; | |
38 | }; | |
39 | ||
40 | struct single_pass_traversal_tag | |
41 | : incrementable_traversal_tag | |
42 | { | |
43 | // single_pass_traversal_tag() {} | |
44 | // single_pass_traversal_tag(std::input_iterator_tag const&) {}; | |
45 | }; | |
46 | ||
47 | struct forward_traversal_tag | |
48 | : single_pass_traversal_tag | |
49 | { | |
50 | // forward_traversal_tag() {} | |
51 | // forward_traversal_tag(std::forward_iterator_tag const&) {}; | |
52 | }; | |
53 | ||
54 | struct bidirectional_traversal_tag | |
55 | : forward_traversal_tag | |
56 | { | |
57 | // bidirectional_traversal_tag() {}; | |
58 | // bidirectional_traversal_tag(std::bidirectional_iterator_tag const&) {}; | |
59 | }; | |
60 | ||
61 | struct random_access_traversal_tag | |
62 | : bidirectional_traversal_tag | |
63 | { | |
64 | // random_access_traversal_tag() {}; | |
65 | // random_access_traversal_tag(std::random_access_iterator_tag const&) {}; | |
66 | }; | |
67 | ||
68 | namespace detail | |
69 | { | |
70 | // | |
71 | // Convert a "strictly old-style" iterator category to a traversal | |
72 | // tag. This is broken out into a separate metafunction to reduce | |
73 | // the cost of instantiating iterator_category_to_traversal, below, | |
74 | // for new-style types. | |
75 | // | |
76 | template <class Cat> | |
77 | struct old_category_to_traversal | |
78 | : mpl::eval_if< | |
79 | is_convertible<Cat,std::random_access_iterator_tag> | |
80 | , mpl::identity<random_access_traversal_tag> | |
81 | , mpl::eval_if< | |
82 | is_convertible<Cat,std::bidirectional_iterator_tag> | |
83 | , mpl::identity<bidirectional_traversal_tag> | |
84 | , mpl::eval_if< | |
85 | is_convertible<Cat,std::forward_iterator_tag> | |
86 | , mpl::identity<forward_traversal_tag> | |
87 | , mpl::eval_if< | |
88 | is_convertible<Cat,std::input_iterator_tag> | |
89 | , mpl::identity<single_pass_traversal_tag> | |
90 | , mpl::eval_if< | |
91 | is_convertible<Cat,std::output_iterator_tag> | |
92 | , mpl::identity<incrementable_traversal_tag> | |
93 | , void | |
94 | > | |
95 | > | |
96 | > | |
97 | > | |
98 | > | |
99 | {}; | |
100 | ||
101 | } // namespace detail | |
102 | ||
103 | // | |
104 | // Convert an iterator category into a traversal tag | |
105 | // | |
106 | template <class Cat> | |
107 | struct iterator_category_to_traversal | |
108 | : mpl::eval_if< // if already convertible to a traversal tag, we're done. | |
109 | is_convertible<Cat,incrementable_traversal_tag> | |
110 | , mpl::identity<Cat> | |
111 | , boost::iterators::detail::old_category_to_traversal<Cat> | |
112 | > | |
113 | {}; | |
114 | ||
115 | // Trait to get an iterator's traversal category | |
116 | template <class Iterator = mpl::_1> | |
117 | struct iterator_traversal | |
118 | : iterator_category_to_traversal< | |
119 | typename boost::detail::iterator_traits<Iterator>::iterator_category | |
120 | > | |
121 | {}; | |
122 | ||
123 | # ifdef BOOST_MPL_CFG_NO_FULL_LAMBDA_SUPPORT | |
124 | // Hack because BOOST_MPL_AUX_LAMBDA_SUPPORT doesn't seem to work | |
125 | // out well. Instantiating the nested apply template also | |
126 | // requires instantiating iterator_traits on the | |
127 | // placeholder. Instead we just specialize it as a metafunction | |
128 | // class. | |
129 | template <> | |
130 | struct iterator_traversal<mpl::_1> | |
131 | { | |
132 | template <class T> | |
133 | struct apply : iterator_traversal<T> | |
134 | {}; | |
135 | }; | |
136 | template <> | |
137 | struct iterator_traversal<mpl::_> | |
138 | : iterator_traversal<mpl::_1> | |
139 | {}; | |
140 | # endif | |
141 | ||
142 | // | |
143 | // Convert an iterator traversal to one of the traversal tags. | |
144 | // | |
145 | template <class Traversal> | |
146 | struct pure_traversal_tag | |
147 | : mpl::eval_if< | |
148 | is_convertible<Traversal,random_access_traversal_tag> | |
149 | , mpl::identity<random_access_traversal_tag> | |
150 | , mpl::eval_if< | |
151 | is_convertible<Traversal,bidirectional_traversal_tag> | |
152 | , mpl::identity<bidirectional_traversal_tag> | |
153 | , mpl::eval_if< | |
154 | is_convertible<Traversal,forward_traversal_tag> | |
155 | , mpl::identity<forward_traversal_tag> | |
156 | , mpl::eval_if< | |
157 | is_convertible<Traversal,single_pass_traversal_tag> | |
158 | , mpl::identity<single_pass_traversal_tag> | |
159 | , mpl::eval_if< | |
160 | is_convertible<Traversal,incrementable_traversal_tag> | |
161 | , mpl::identity<incrementable_traversal_tag> | |
162 | , void | |
163 | > | |
164 | > | |
165 | > | |
166 | > | |
167 | > | |
168 | { | |
169 | }; | |
170 | ||
171 | // | |
172 | // Trait to retrieve one of the iterator traversal tags from the iterator category or traversal. | |
173 | // | |
174 | template <class Iterator = mpl::_1> | |
175 | struct pure_iterator_traversal | |
176 | : pure_traversal_tag<typename iterator_traversal<Iterator>::type> | |
177 | {}; | |
178 | ||
179 | # ifdef BOOST_MPL_CFG_NO_FULL_LAMBDA_SUPPORT | |
180 | template <> | |
181 | struct pure_iterator_traversal<mpl::_1> | |
182 | { | |
183 | template <class T> | |
184 | struct apply : pure_iterator_traversal<T> | |
185 | {}; | |
186 | }; | |
187 | template <> | |
188 | struct pure_iterator_traversal<mpl::_> | |
189 | : pure_iterator_traversal<mpl::_1> | |
190 | {}; | |
191 | # endif | |
192 | ||
193 | } // namespace iterators | |
194 | ||
195 | using iterators::no_traversal_tag; | |
196 | using iterators::incrementable_traversal_tag; | |
197 | using iterators::single_pass_traversal_tag; | |
198 | using iterators::forward_traversal_tag; | |
199 | using iterators::bidirectional_traversal_tag; | |
200 | using iterators::random_access_traversal_tag; | |
201 | using iterators::iterator_category_to_traversal; | |
202 | using iterators::iterator_traversal; | |
203 | ||
204 | // This import is needed for backward compatibility with Boost.Range: | |
205 | // boost/range/detail/demote_iterator_traversal_tag.hpp | |
206 | // It should be removed when that header is fixed. | |
207 | namespace detail { | |
208 | using iterators::pure_traversal_tag; | |
209 | } // namespace detail | |
210 | ||
211 | } // namespace boost | |
212 | ||
213 | #include <boost/iterator/detail/config_undef.hpp> | |
214 | ||
215 | #endif // BOOST_ITERATOR_CATEGORIES_HPP |