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<title>Concept InputIterator</title>
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<div class="refentry">
<a name="InputIterator"></a><div class="titlepage"></div>
<div class="refnamediv">
<h2><span class="refentrytitle">Concept InputIterator</span></h2>
<p>InputIterator</p>
</div>
<div class="refsect1">
<a name="idp615178544"></a><h2>Description</h2>
<p>An input iterator is an iterator that can read through a sequence of
values. It is single-pass (old values of the iterator cannot be
re-used), and read-only.</p>
<p>An input iterator represents a position in a sequence. Therefore, the
iterator can point into the sequence (returning a value when dereferenced
and being incrementable), or be off-the-end (and not dereferenceable or
incrementable).</p>
</div>
<div class="refsect1">
<a name="idp615180288"></a><h2>Refinement of</h2>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem"><p><a class="link" href="Assignable.html" title="Concept Assignable">Assignable</a></p></li>
<li class="listitem"><p><a class="link" href="DefaultConstructible.html" title="Concept DefaultConstructible">DefaultConstructible</a></p></li>
<li class="listitem"><p><a class="link" href="EqualityComparable.html" title="Concept EqualityComparable">EqualityComparable</a></p></li>
</ul></div>
</div>
<div class="refsect1">
<a name="idp615183616"></a><h2>Associated types</h2>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p><span class="bold"><strong>value_type</strong></span></p>
<pre class="literallayout">std::iterator_traits<Iter>::value_type</pre>
<p>The value type of the iterator (not necessarily what
<code class="computeroutput">*i</code> returns)</p>
</li>
<li class="listitem">
<p><span class="bold"><strong>difference_type</strong></span></p>
<pre class="literallayout">std::iterator_traits<Iter>::difference_type</pre>
<p>The difference type of the iterator</p>
</li>
<li class="listitem">
<p><span class="bold"><strong>category</strong></span></p>
<pre class="literallayout">std::iterator_traits<Iter>::iterator_category</pre>
<p>The category of the iterator</p>
</li>
</ul></div>
</div>
<div class="refsect1">
<a name="idp615190960"></a><h2>Notation</h2>
<div class="variablelist"><dl class="variablelist">
<dt><span class="term">Iter</span></dt>
<dd>A type playing the role of iterator-type in the <a class="link" href="InputIterator.html" title="Concept InputIterator">InputIterator</a> concept.</dd>
<dt>
<span class="term"><code class="varname">i</code>, </span><span class="term"><code class="varname">j</code></span>
</dt>
<dd>Objects of type Iter</dd>
<dt><span class="term"><code class="varname">x</code></span></dt>
<dd>Object of type value_type</dd>
</dl></div>
</div>
<div class="refsect1">
<a name="idp615195456"></a><h2>Type expressions</h2>
<div class="variablelist"><dl class="variablelist">
<dt><span class="term">Category tag</span></dt>
<dd><p><span class="type">category</span> must be
derived from <span class="type">std::input_iterator_tag</span>, a model of <a class="link" href="DefaultConstructible.html" title="Concept DefaultConstructible">DefaultConstructible</a>, and a model of <a class="link" href="CopyConstructible.html" title="Concept CopyConstructible">CopyConstructible</a>.
</p></dd>
<dt><span class="term">Value type copy constructibility</span></dt>
<dd><p><span class="type">value_type</span> must be
a model of <a class="link" href="CopyConstructible.html" title="Concept CopyConstructible">CopyConstructible</a>.
</p></dd>
<dt><span class="term">Difference type properties</span></dt>
<dd><p><span class="type">difference_type</span> must be
a model of <a class="link" href="SignedInteger.html" title="Concept SignedInteger">SignedInteger</a>.
</p></dd>
</dl></div>
</div>
<div class="refsect1">
<a name="idp615203264"></a><h2>Valid expressions</h2>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>Name</th>
<th>Expression</th>
<th>Type</th>
<th>Precondition</th>
<th>Semantics</th>
<th>Postcondition</th>
</tr></thead>
<tbody>
<tr>
<td><p>Dereference</p></td>
<td><p>*i</p></td>
<td><p>Convertible to <span class="type">value_type</span></p></td>
<td><p><code class="computeroutput">i</code> is incrementable (not
off-the-end)</p></td>
<td> </td>
<td> </td>
</tr>
<tr>
<td><p>Preincrement</p></td>
<td><p>++i</p></td>
<td><p><span class="type">Iter &</span></p></td>
<td><p><code class="computeroutput">i</code> is incrementable (not
off-the-end)</p></td>
<td> </td>
<td> </td>
</tr>
<tr>
<td><p>Postincrement</p></td>
<td><p>i++</p></td>
<td><p></p></td>
<td><p><code class="computeroutput">i</code> is incrementable (not
off-the-end)</p></td>
<td><p>Equivalent to <code class="computeroutput">(void)(++i)</code></p></td>
<td><p><code class="computeroutput">i</code> is dereferenceable or
off-the-end</p></td>
</tr>
<tr>
<td><p>Postincrement and dereference</p></td>
<td><p>*i++</p></td>
<td><p>Convertible to <span class="type">value_type</span></p></td>
<td><p><code class="computeroutput">i</code> is incrementable (not
off-the-end)</p></td>
<td><p>Equivalent to <code class="computeroutput">{value_type t = *i; ++i; return t;}</code></p></td>
<td><p><code class="computeroutput">i</code> is dereferenceable or
off-the-end</p></td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect1">
<a name="idp615220592"></a><h2>Complexity</h2>
<p>
All iterator operations must take amortized constant time.
</p>
</div>
<div class="refsect1">
<a name="idp615221344"></a><h2>Models</h2>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><span class="simplelist"><span class="type">std::istream_iterator</span></span></li></ul></div>
</div>
<div class="refsect1">
<a name="idp615222832"></a><h2>See also</h2>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem"><p><a class="link" href="DefaultConstructible.html" title="Concept DefaultConstructible">DefaultConstructible</a></p></li>
<li class="listitem"><p><a class="link" href="EqualityComparable.html" title="Concept EqualityComparable">EqualityComparable</a></p></li>
</ul></div>
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<td align="right"><div class="copyright-footer">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<p>Distributed under the Boost Software License, Version 1.0.
(See accompanying file <code class="filename">LICENSE_1_0.txt</code> or copy at
<a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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<p>This product includes software developed at the University
of Notre Dame and the Pervasive Technology Labs at Indiana
University. For technical information contact Andrew Lumsdaine
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administrative and license questions contact the Advanced
Research and Technology Institute at 351 West 10th Street.
Indianapolis, Indiana 46202, phone 317-278-4100, fax
317-274-5902.</p>
<p>Some concepts based on versions from the MTL draft manual
and Boost Graph and Property Map documentation, the SGI Standard
Template Library documentation and the Hewlett-Packard STL,
under the following license:
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