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7 | <title>The MPL Reference Manual: iterator_category</title> | |
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12 | <td class="header-group page-location"><a href="../refmanual.html" class="navigation-link">Front Page</a> / <a href="./iterators.html" class="navigation-link">Iterators</a> / <a href="./iterator-metafunctions.html" class="navigation-link">Iterator Metafunctions</a> / <a href="./iterator-category.html" class="navigation-link">iterator_category</a></td> | |
13 | </tr></table><div class="header-separator"></div> | |
14 | <div class="section" id="iterator-category"> | |
15 | <h1><a class="toc-backref" href="./iterator-metafunctions.html#id1459">iterator_category</a></h1> | |
16 | <div class="section" id="id445"> | |
17 | <h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> | |
18 | <pre class="literal-block"> | |
19 | template< | |
20 | typename Iterator | |
21 | > | |
22 | struct <a href="./iterator-category.html" class="identifier">iterator_category</a> | |
23 | { | |
24 | typedef typename Iterator::category type; | |
25 | }; | |
26 | </pre> | |
27 | </div> | |
28 | <div class="section" id="id446"> | |
29 | <h3><a class="subsection-title" href="#description" name="description">Description</a></h3> | |
30 | <p>Returns one of the following iterator category tags:</p> | |
31 | <ul class="simple"> | |
32 | <li><tt class="literal"><span class="pre">forward_iterator_tag</span></tt></li> | |
33 | <li><tt class="literal"><span class="pre">bidirectional_iterator_tag</span></tt></li> | |
34 | <li><tt class="literal"><span class="pre">random_access_iterator_tag</span></tt></li> | |
35 | </ul> | |
36 | </div> | |
37 | <div class="section" id="id447"> | |
38 | <h3><a class="subsection-title" href="#header" name="header">Header</a></h3> | |
39 | <pre class="literal-block"> | |
40 | #include <<a href="../../../../boost/mpl/iterator_category.hpp" class="header">boost/mpl/iterator_category.hpp</a>> | |
41 | #include <<a href="../../../../boost/mpl/iterator_tags.hpp" class="header">boost/mpl/iterator_tags.hpp</a>> | |
42 | </pre> | |
43 | </div> | |
44 | <div class="section" id="id448"> | |
45 | <h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> | |
46 | <table border="1" class="docutils table"> | |
47 | <colgroup> | |
48 | <col width="19%" /> | |
49 | <col width="28%" /> | |
50 | <col width="53%" /> | |
51 | </colgroup> | |
52 | <thead valign="bottom"> | |
53 | <tr><th class="head">Parameter</th> | |
54 | <th class="head">Requirement</th> | |
55 | <th class="head">Description</th> | |
56 | </tr> | |
57 | </thead> | |
58 | <tbody valign="top"> | |
59 | <tr><td><tt class="literal"><span class="pre">Iterator</span></tt></td> | |
60 | <td><a class="reference internal" href="./forward-iterator.html">Forward Iterator</a></td> | |
61 | <td>The iterator to obtain a category for.</td> | |
62 | </tr> | |
63 | </tbody> | |
64 | </table> | |
65 | </div> | |
66 | <div class="section" id="id449"> | |
67 | <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> | |
68 | <p>For any <a class="reference internal" href="./forward-iterator.html">Forward Iterator</a>s <tt class="literal"><span class="pre">iter</span></tt>:</p> | |
69 | <pre class="literal-block"> | |
70 | typedef <a href="./iterator-category.html" class="identifier">iterator_category</a><iter>::type tag; | |
71 | </pre> | |
72 | <table class="docutils field-list" frame="void" rules="none"> | |
73 | <col class="field-name" /> | |
74 | <col class="field-body" /> | |
75 | <tbody valign="top"> | |
76 | <tr class="field"><th class="field-name">Return type:</th><td class="field-body"><p class="first"><a class="reference internal" href="./integral-constant.html">Integral Constant</a>.</p> | |
77 | </td> | |
78 | </tr> | |
79 | <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first"><tt class="literal"><span class="pre">tag</span></tt> is <tt class="literal"><span class="pre">forward_iterator_tag</span></tt> if <tt class="literal"><span class="pre">iter</span></tt> is a model of <a class="reference internal" href="./forward-iterator.html">Forward Iterator</a>, | |
80 | <tt class="literal"><span class="pre">bidirectional_iterator_tag</span></tt> if <tt class="literal"><span class="pre">iter</span></tt> is a model of <a class="reference internal" href="./bidirectional-iterator.html">Bidirectional Iterator</a>, | |
81 | or <tt class="literal"><span class="pre">random_access_iterator_tag</span></tt> if <tt class="literal"><span class="pre">iter</span></tt> is a model of <a class="reference internal" href="./random-access-iterator.html">Random Access Iterator</a>;</p> | |
82 | </td> | |
83 | </tr> | |
84 | <tr class="field"><th class="field-name">Postcondition:</th><td class="field-body"><dl class="first last docutils"> | |
85 | <dt><tt class="literal"><span class="pre">forward_iterator_tag::value</span> <span class="pre"><</span> <span class="pre">bidirectional_iterator_tag::value</span></tt>,</dt> | |
86 | <dd><p class="first last"><tt class="literal"><span class="pre">bidirectional_iterator_tag::value</span> <span class="pre"><</span> <span class="pre">random_access_iterator_tag::value</span></tt>.</p> | |
87 | </dd> | |
88 | </dl> | |
89 | </td> | |
90 | </tr> | |
91 | </tbody> | |
92 | </table> | |
93 | </div> | |
94 | <div class="section" id="id450"> | |
95 | <h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3> | |
96 | <p>Amortized constant time.</p> | |
97 | </div> | |
98 | <div class="section" id="id451"> | |
99 | <h3><a class="subsection-title" href="#example" name="example">Example</a></h3> | |
100 | <pre class="literal-block"> | |
101 | template< typename Tag, typename Iterator > | |
102 | struct algorithm_impl | |
103 | { | |
104 | // <em>O(n)</em> implementation | |
105 | }; | |
106 | ||
107 | template< typename Iterator > | |
108 | struct algorithm_impl<random_access_iterator_tag,Iterator> | |
109 | { | |
110 | // <em>O(1)</em> implementation | |
111 | }; | |
112 | ||
113 | template< typename Iterator > | |
114 | struct algorithm | |
115 | : algorithm_impl< | |
116 | <a href="./iterator-category.html" class="identifier">iterator_category</a><Iterator>::type | |
117 | , Iterator | |
118 | > | |
119 | { | |
120 | }; | |
121 | </pre> | |
122 | </div> | |
123 | <div class="section" id="id452"> | |
124 | <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3> | |
125 | <p><a class="reference internal" href="./iterators.html">Iterators</a>, <a class="reference internal" href="./begin.html">begin</a> / <a class="reference internal" href="./end.html">end</a>, <a class="reference internal" href="./advance.html">advance</a>, <a class="reference internal" href="./distance.html">distance</a>, <a class="reference internal" href="./next.html">next</a></p> | |
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