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7 | <title>Iterator Traits</title> | |
8 | <meta name="author" content="David Abrahams" /> | |
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15 | <div class="document" id="iterator-traits"> | |
16 | <h1 class="title">Iterator Traits</h1> | |
17 | <table class="docinfo" frame="void" rules="none"> | |
18 | <col class="docinfo-name" /> | |
19 | <col class="docinfo-content" /> | |
20 | <tbody valign="top"> | |
21 | <tr><th class="docinfo-name">Author:</th> | |
22 | <td>David Abrahams</td></tr> | |
23 | <tr><th class="docinfo-name">Contact:</th> | |
24 | <td><a class="first last reference external" href="mailto:dave@boost-consulting.com">dave@boost-consulting.com</a></td></tr> | |
25 | <tr><th class="docinfo-name">Organization:</th> | |
26 | <td><a class="first last reference external" href="http://www.boost-consulting.com">Boost Consulting</a></td></tr> | |
27 | <tr><th class="docinfo-name">Date:</th> | |
28 | <td>$Date$</td></tr> | |
29 | <tr><th class="docinfo-name">Copyright:</th> | |
30 | <td>Copyright David Abrahams 2004.</td></tr> | |
31 | </tbody> | |
32 | </table> | |
33 | <!-- Distributed under the Boost --> | |
34 | <!-- Software License, Version 1.0. (See accompanying --> | |
35 | <!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) --> | |
36 | <table class="docutils field-list" frame="void" rules="none"> | |
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38 | <col class="field-body" /> | |
39 | <tbody valign="top"> | |
40 | <tr class="field"><th class="field-name">abstract:</th><td class="field-body">Header <tt class="docutils literal"><boost/iterator/iterator_traits.hpp></tt> provides | |
41 | the ability to access an iterator's associated types using | |
42 | MPL-compatible <a class="reference external" href="../../mpl/doc/index.html#metafunctions">metafunctions</a>.</td> | |
43 | </tr> | |
44 | </tbody> | |
45 | </table> | |
46 | <div class="section" id="overview"> | |
47 | <h1>Overview</h1> | |
48 | <p><tt class="docutils literal"><span class="pre">std::iterator_traits</span></tt> provides access to five associated types | |
49 | of any iterator: its <tt class="docutils literal">value_type</tt>, <tt class="docutils literal">reference</tt>, <tt class="docutils literal">pointer</tt>, | |
50 | <tt class="docutils literal">iterator_category</tt>, and <tt class="docutils literal">difference_type</tt>. Unfortunately, | |
51 | such a "multi-valued" traits template can be difficult to use in a | |
52 | metaprogramming context. <tt class="docutils literal"><boost/iterator/iterator_traits.hpp></tt> | |
53 | provides access to these types using a standard <a class="reference external" href="../../mpl/doc/index.html#metafunctions">metafunctions</a>.</p> | |
54 | </div> | |
55 | <div class="section" id="summary"> | |
56 | <h1>Summary</h1> | |
57 | <p>Header <tt class="docutils literal"><boost/iterator/iterator_traits.hpp></tt>:</p> | |
58 | <pre class="literal-block"> | |
59 | template <class Iterator> | |
60 | struct iterator_value | |
61 | { | |
62 | typedef typename | |
63 | std::iterator_traits<Iterator>::value_type | |
64 | type; | |
65 | }; | |
66 | ||
67 | template <class Iterator> | |
68 | struct iterator_reference | |
69 | { | |
70 | typedef typename | |
71 | std::iterator_traits<Iterator>::reference | |
72 | type; | |
73 | }; | |
74 | ||
75 | ||
76 | template <class Iterator> | |
77 | struct iterator_pointer | |
78 | { | |
79 | typedef typename | |
80 | std::iterator_traits<Iterator>::pointer | |
81 | type; | |
82 | }; | |
83 | ||
84 | template <class Iterator> | |
85 | struct iterator_difference | |
86 | { | |
87 | typedef typename | |
88 | detail::iterator_traits<Iterator>::difference_type | |
89 | type; | |
90 | }; | |
91 | ||
92 | template <class Iterator> | |
93 | struct iterator_category | |
94 | { | |
95 | typedef typename | |
96 | detail::iterator_traits<Iterator>::iterator_category | |
97 | type; | |
98 | }; | |
99 | </pre> | |
100 | </div> | |
101 | </div> | |
102 | <div class="footer"> | |
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