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4<title>Concept InputIterator</title>
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25<div class="refentry" lang="en">
26<a name="InputIterator"></a><div class="titlepage"></div>
27<div class="refnamediv">
28<h2><span class="refentrytitle">Concept InputIterator</span></h2>
29<p>InputIterator</p>
30</div>
31<div class="refsect1" lang="en">
32<a name="id942539"></a><h2>Description</h2>
33<p>An input iterator is an iterator that can read through a sequence of
34  values.  It is single-pass (old values of the iterator cannot be
35  re-used), and read-only.</p>
36<p>An input iterator represents a position in a sequence.  Therefore, the
37  iterator can point into the sequence (returning a value when dereferenced
38  and being incrementable), or be off-the-end (and not dereferenceable or
39  incrementable).</p>
40</div>
41<div class="refsect1" lang="en">
42<a name="id942557"></a><h2>Refinement of</h2>
43<div class="itemizedlist"><ul type="disc">
44<li><p><a href="Assignable.html" title="Concept Assignable">Assignable</a></p></li>
45<li><p><a href="DefaultConstructible.html" title="Concept DefaultConstructible">DefaultConstructible</a></p></li>
46<li><p><a href="EqualityComparable.html" title="Concept EqualityComparable">EqualityComparable</a></p></li>
47</ul></div>
48</div>
49<div class="refsect1" lang="en">
50<a name="id942586"></a><h2>Associated types</h2>
51<div class="itemizedlist"><ul type="disc">
52<li>
53<p><span class="bold"><strong>value_type</strong></span></p>
54<pre class="literallayout">std::iterator_traits&lt;Iter&gt;::value_type</pre>
55<p>The value type of the iterator (not necessarily what
56    <code class="computeroutput">*i</code> returns)</p>
57</li>
58<li>
59<p><span class="bold"><strong>difference_type</strong></span></p>
60<pre class="literallayout">std::iterator_traits&lt;Iter&gt;::difference_type</pre>
61<p>The difference type of the iterator</p>
62</li>
63<li>
64<p><span class="bold"><strong>category</strong></span></p>
65<pre class="literallayout">std::iterator_traits&lt;Iter&gt;::iterator_category</pre>
66<p>The category of the iterator</p>
67</li>
68</ul></div>
69</div>
70<div class="refsect1" lang="en">
71<a name="id942649"></a><h2>Notation</h2>
72<div class="variablelist"><dl>
73<dt><span class="term">Iter</span></dt>
74<dd>A type playing the role of iterator-type in the <a href="InputIterator.html" title="Concept InputIterator">InputIterator</a> concept.</dd>
75<dt>
76<span class="term"><code class="varname">i</code>, </span><span class="term"><code class="varname">j</code></span>
77</dt>
78<dd>Objects of type Iter</dd>
79<dt><span class="term"><code class="varname">x</code></span></dt>
80<dd>Object of type value_type</dd>
81</dl></div>
82</div>
83<div class="refsect1" lang="en">
84<a name="id942687"></a><h2>Type expressions</h2>
85<div class="variablelist"><dl>
86<dt><span class="term">Category tag</span></dt>
87<dd><p><span class="type">category</span> must be
88                  derived from <span class="type">std::input_iterator_tag</span>,  a model  of <a href="DefaultConstructible.html" title="Concept DefaultConstructible">DefaultConstructible</a>,  and  a model  of <a href="CopyConstructible.html" title="Concept CopyConstructible">CopyConstructible</a>.
89                </p></dd>
90<dt><span class="term">Value type copy constructibility</span></dt>
91<dd><p><span class="type">value_type</span> must be
92                   a model  of <a href="CopyConstructible.html" title="Concept CopyConstructible">CopyConstructible</a>.
93                </p></dd>
94<dt><span class="term">Difference type properties</span></dt>
95<dd><p><span class="type">difference_type</span> must be
96                   a model  of <a href="SignedInteger.html" title="Concept SignedInteger">SignedInteger</a>.
97                </p></dd>
98</dl></div>
99</div>
100<div class="refsect1" lang="en">
101<a name="id942757"></a><h2>Valid expressions</h2>
102<div class="informaltable"><table class="table">
103<colgroup>
104<col>
105<col>
106<col>
107<col>
108<col>
109<col>
110</colgroup>
111<thead><tr>
112<th>Name</th>
113<th>Expression</th>
114<th>Type</th>
115<th>Precondition</th>
116<th>Semantics</th>
117<th>Postcondition</th>
118</tr></thead>
119<tbody>
120<tr>
121<td><p>Dereference</p></td>
122<td><p>*i</p></td>
123<td><p>Convertible to <span class="type">value_type</span></p></td>
124<td><p><code class="computeroutput">i</code> is incrementable (not
125    off-the-end)</p></td>
126<td> </td>
127<td> </td>
128</tr>
129<tr>
130<td><p>Preincrement</p></td>
131<td><p>++i</p></td>
132<td><p><span class="type">Iter &amp;</span></p></td>
133<td><p><code class="computeroutput">i</code> is incrementable (not
134    off-the-end)</p></td>
135<td> </td>
136<td> </td>
137</tr>
138<tr>
139<td><p>Postincrement</p></td>
140<td><p>i++</p></td>
141<td><p></p></td>
142<td><p><code class="computeroutput">i</code> is incrementable (not
143    off-the-end)</p></td>
144<td><p>Equivalent to <code class="computeroutput">(void)(++i)</code></p></td>
145<td><p><code class="computeroutput">i</code> is dereferenceable or
146    off-the-end</p></td>
147</tr>
148<tr>
149<td><p>Postincrement and dereference</p></td>
150<td><p>*i++</p></td>
151<td><p>Convertible to <span class="type">value_type</span></p></td>
152<td><p><code class="computeroutput">i</code> is incrementable (not
153    off-the-end)</p></td>
154<td><p>Equivalent to <code class="computeroutput">{value_type t = *i; ++i; return t;}</code></p></td>
155<td><p><code class="computeroutput">i</code> is dereferenceable or
156    off-the-end</p></td>
157</tr>
158</tbody>
159</table></div>
160</div>
161<div class="refsect1" lang="en">
162<a name="id942903"></a><h2>Complexity</h2>
163<p>
164  All iterator operations must take amortized constant time.
165  </p>
166</div>
167<div class="refsect1" lang="en">
168<a name="id942910"></a><h2>Models</h2>
169<div class="itemizedlist"><ul type="disc"><li><span class="simplelist"><span class="type">std::istream_iterator</span></span></li></ul></div>
170</div>
171<div class="refsect1" lang="en">
172<a name="id942922"></a><h2>See also</h2>
173<div class="itemizedlist"><ul type="disc">
174<li><p><a href="DefaultConstructible.html" title="Concept DefaultConstructible">DefaultConstructible</a></p></li>
175<li><p><a href="EqualityComparable.html" title="Concept EqualityComparable">EqualityComparable</a></p></li>
176<li><p><a href="ForwardIterator.html" title="Concept ForwardIterator">ForwardIterator</a></p></li>
177<li><p><a href="OutputIterator.html" title="Concept OutputIterator">OutputIterator</a></p></li>
178</ul></div>
179</div>
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183<td align="right"><small>Copyright © 2001, 2002 Indiana University<br>Copyright © 2000, 2001 University of Notre Dame du Lac<br>Copyright © 2000 Jeremy Siek, Lie-Quan Lee, Andrew Lumsdaine<br>Copyright © 1996-1999 Silicon Graphics Computer Systems, Inc.<br>Copyright © 1994 Hewlett-Packard Company</small></td>
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