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1 | // Copyright David Abrahams 2003. Use, modification and distribution is |
2 | // subject to the Boost Software License, Version 1.0. (See accompanying | |
3 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
4 | #ifndef FACADE_ITERATOR_CATEGORY_DWA20031118_HPP | |
5 | # define FACADE_ITERATOR_CATEGORY_DWA20031118_HPP | |
6 | ||
92f5a8d4 TL |
7 | # include <boost/core/use_default.hpp> |
8 | ||
7c673cae FG |
9 | # include <boost/iterator/iterator_categories.hpp> |
10 | ||
11 | # include <boost/mpl/or.hpp> // used in iterator_tag inheritance logic | |
12 | # include <boost/mpl/and.hpp> | |
13 | # include <boost/mpl/if.hpp> | |
14 | # include <boost/mpl/eval_if.hpp> | |
15 | # include <boost/mpl/identity.hpp> | |
16 | # include <boost/mpl/assert.hpp> | |
17 | ||
18 | # include <boost/type_traits/is_same.hpp> | |
19 | # include <boost/type_traits/is_const.hpp> | |
20 | # include <boost/type_traits/is_reference.hpp> | |
21 | # include <boost/type_traits/is_convertible.hpp> | |
22 | ||
23 | # include <boost/type_traits/is_same.hpp> | |
24 | ||
25 | # include <boost/iterator/detail/config_def.hpp> // try to keep this last | |
26 | ||
27 | # ifdef BOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY | |
28 | # include <boost/detail/indirect_traits.hpp> | |
29 | # endif | |
30 | ||
31 | // | |
32 | // iterator_category deduction for iterator_facade | |
33 | // | |
34 | ||
35 | namespace boost { | |
36 | namespace iterators { | |
37 | ||
92f5a8d4 | 38 | using boost::use_default; |
7c673cae FG |
39 | |
40 | namespace detail { | |
41 | ||
42 | struct input_output_iterator_tag | |
43 | : std::input_iterator_tag | |
44 | { | |
45 | // Using inheritance for only input_iterator_tag helps to avoid | |
46 | // ambiguities when a stdlib implementation dispatches on a | |
47 | // function which is overloaded on both input_iterator_tag and | |
48 | // output_iterator_tag, as STLPort does, in its __valid_range | |
49 | // function. I claim it's better to avoid the ambiguity in these | |
50 | // cases. | |
51 | operator std::output_iterator_tag() const | |
52 | { | |
53 | return std::output_iterator_tag(); | |
54 | } | |
55 | }; | |
56 | ||
57 | // | |
58 | // True iff the user has explicitly disabled writability of this | |
59 | // iterator. Pass the iterator_facade's Value parameter and its | |
60 | // nested ::reference type. | |
61 | // | |
62 | template <class ValueParam, class Reference> | |
63 | struct iterator_writability_disabled | |
64 | # ifdef BOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY // Adding Thomas' logic? | |
65 | : mpl::or_< | |
66 | is_const<Reference> | |
67 | , boost::detail::indirect_traits::is_reference_to_const<Reference> | |
68 | , is_const<ValueParam> | |
69 | > | |
70 | # else | |
71 | : is_const<ValueParam> | |
72 | # endif | |
73 | {}; | |
74 | ||
75 | ||
76 | // | |
77 | // Convert an iterator_facade's traversal category, Value parameter, | |
78 | // and ::reference type to an appropriate old-style category. | |
79 | // | |
80 | // Due to changeset 21683, this now never results in a category convertible | |
81 | // to output_iterator_tag. | |
82 | // | |
83 | // Change at: https://svn.boost.org/trac/boost/changeset/21683 | |
84 | template <class Traversal, class ValueParam, class Reference> | |
85 | struct iterator_facade_default_category | |
86 | : mpl::eval_if< | |
87 | mpl::and_< | |
88 | is_reference<Reference> | |
89 | , is_convertible<Traversal,forward_traversal_tag> | |
90 | > | |
91 | , mpl::eval_if< | |
92 | is_convertible<Traversal,random_access_traversal_tag> | |
93 | , mpl::identity<std::random_access_iterator_tag> | |
94 | , mpl::if_< | |
95 | is_convertible<Traversal,bidirectional_traversal_tag> | |
96 | , std::bidirectional_iterator_tag | |
97 | , std::forward_iterator_tag | |
98 | > | |
99 | > | |
100 | , typename mpl::eval_if< | |
101 | mpl::and_< | |
102 | is_convertible<Traversal, single_pass_traversal_tag> | |
103 | ||
104 | // check for readability | |
105 | , is_convertible<Reference, ValueParam> | |
106 | > | |
107 | , mpl::identity<std::input_iterator_tag> | |
108 | , mpl::identity<Traversal> | |
109 | > | |
110 | > | |
111 | { | |
112 | }; | |
113 | ||
114 | // True iff T is convertible to an old-style iterator category. | |
115 | template <class T> | |
116 | struct is_iterator_category | |
117 | : mpl::or_< | |
118 | is_convertible<T,std::input_iterator_tag> | |
119 | , is_convertible<T,std::output_iterator_tag> | |
120 | > | |
121 | { | |
122 | }; | |
123 | ||
124 | template <class T> | |
125 | struct is_iterator_traversal | |
126 | : is_convertible<T,incrementable_traversal_tag> | |
127 | {}; | |
128 | ||
129 | // | |
130 | // A composite iterator_category tag convertible to Category (a pure | |
131 | // old-style category) and Traversal (a pure traversal tag). | |
132 | // Traversal must be a strict increase of the traversal power given by | |
133 | // Category. | |
134 | // | |
135 | template <class Category, class Traversal> | |
136 | struct iterator_category_with_traversal | |
137 | : Category, Traversal | |
138 | { | |
139 | // Make sure this isn't used to build any categories where | |
140 | // convertibility to Traversal is redundant. Should just use the | |
141 | // Category element in that case. | |
142 | BOOST_MPL_ASSERT_NOT(( | |
143 | is_convertible< | |
144 | typename iterator_category_to_traversal<Category>::type | |
145 | , Traversal | |
146 | >)); | |
147 | ||
148 | BOOST_MPL_ASSERT((is_iterator_category<Category>)); | |
149 | BOOST_MPL_ASSERT_NOT((is_iterator_category<Traversal>)); | |
150 | BOOST_MPL_ASSERT_NOT((is_iterator_traversal<Category>)); | |
151 | # if !BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1310)) | |
152 | BOOST_MPL_ASSERT((is_iterator_traversal<Traversal>)); | |
153 | # endif | |
154 | }; | |
155 | ||
156 | // Computes an iterator_category tag whose traversal is Traversal and | |
157 | // which is appropriate for an iterator | |
158 | template <class Traversal, class ValueParam, class Reference> | |
159 | struct facade_iterator_category_impl | |
160 | { | |
161 | BOOST_MPL_ASSERT_NOT((is_iterator_category<Traversal>)); | |
162 | ||
163 | typedef typename iterator_facade_default_category< | |
164 | Traversal,ValueParam,Reference | |
165 | >::type category; | |
166 | ||
167 | typedef typename mpl::if_< | |
168 | is_same< | |
169 | Traversal | |
170 | , typename iterator_category_to_traversal<category>::type | |
171 | > | |
172 | , category | |
173 | , iterator_category_with_traversal<category,Traversal> | |
174 | >::type type; | |
175 | }; | |
176 | ||
177 | // | |
178 | // Compute an iterator_category for iterator_facade | |
179 | // | |
180 | template <class CategoryOrTraversal, class ValueParam, class Reference> | |
181 | struct facade_iterator_category | |
182 | : mpl::eval_if< | |
183 | is_iterator_category<CategoryOrTraversal> | |
184 | , mpl::identity<CategoryOrTraversal> // old-style categories are fine as-is | |
185 | , facade_iterator_category_impl<CategoryOrTraversal,ValueParam,Reference> | |
186 | > | |
187 | { | |
188 | }; | |
189 | ||
190 | }}} // namespace boost::iterators::detail | |
191 | ||
192 | # include <boost/iterator/detail/config_undef.hpp> | |
193 | ||
194 | #endif // FACADE_ITERATOR_CATEGORY_DWA20031118_HPP |