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
24namespace boost {
25namespace iterators {
26
27//
28// Traversal Categories
29//
30
31struct no_traversal_tag {};
32
33struct incrementable_traversal_tag
34 : no_traversal_tag
35{
36// incrementable_traversal_tag() {}
37// incrementable_traversal_tag(std::output_iterator_tag const&) {};
38};
39
40struct 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
47struct forward_traversal_tag
48 : single_pass_traversal_tag
49{
50// forward_traversal_tag() {}
51// forward_traversal_tag(std::forward_iterator_tag const&) {};
52};
53
54struct bidirectional_traversal_tag
55 : forward_traversal_tag
56{
57// bidirectional_traversal_tag() {};
58// bidirectional_traversal_tag(std::bidirectional_iterator_tag const&) {};
59};
60
61struct 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
68namespace 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//
106template <class Cat>
107struct 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
116template <class Iterator = mpl::_1>
117struct 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.
129template <>
130struct iterator_traversal<mpl::_1>
131{
132 template <class T>
133 struct apply : iterator_traversal<T>
134 {};
135};
136template <>
137struct 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//
145template <class Traversal>
146struct 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//
174template <class Iterator = mpl::_1>
175struct pure_iterator_traversal
176 : pure_traversal_tag<typename iterator_traversal<Iterator>::type>
177{};
178
179# ifdef BOOST_MPL_CFG_NO_FULL_LAMBDA_SUPPORT
180template <>
181struct pure_iterator_traversal<mpl::_1>
182{
183 template <class T>
184 struct apply : pure_iterator_traversal<T>
185 {};
186};
187template <>
188struct pure_iterator_traversal<mpl::_>
189 : pure_iterator_traversal<mpl::_1>
190{};
191# endif
192
193} // namespace iterators
194
195using iterators::no_traversal_tag;
196using iterators::incrementable_traversal_tag;
197using iterators::single_pass_traversal_tag;
198using iterators::forward_traversal_tag;
199using iterators::bidirectional_traversal_tag;
200using iterators::random_access_traversal_tag;
201using iterators::iterator_category_to_traversal;
202using 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.
207namespace detail {
208using 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
216