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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="idm45853371055952"></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="idm45853371054208"></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="idm45853371050640"></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&lt;Iter&gt;::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&lt;Iter&gt;::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&lt;Iter&gt;::iterator_category</pre>
<p>The category of the iterator</p>
</li>
</ul></div>
</div>
<div class="refsect1">
<a name="idm45853371043104"></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="idm45853365540624"></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="idm45853365534160"></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>&#160;</td>
<td>&#160;</td>
</tr>
<tr>
<td><p>Preincrement</p></td>
<td><p>++i</p></td>
<td><p><span class="type">Iter &amp;</span></p></td>
<td><p><code class="computeroutput">i</code> is incrementable (not
    off-the-end)</p></td>
<td>&#160;</td>
<td>&#160;</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="idm45853365518176"></a><h2>Complexity</h2>
<p>
  All iterator operations must take amortized constant time.
  </p>
</div>
<div class="refsect1">
<a name="idm45853365517536"></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="idm45853365516144"></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>
<li class="listitem"><p><a class="link" href="ForwardIterator.html" title="Concept ForwardIterator">ForwardIterator</a></p></li>
<li class="listitem"><p><a class="link" href="OutputIterator.html" title="Concept OutputIterator">OutputIterator</a></p></li>
</ul></div>
</div>
</div>
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<td align="right"><div class="copyright-footer">Copyright &#169; 2001, 2002 Indiana University<br>Copyright &#169; 2000, 2001 University of Notre Dame du Lac<br>Copyright &#169; 2000 Jeremy Siek, Lie-Quan Lee, Andrew Lumsdaine<br>Copyright &#169; 1996-1999 Silicon Graphics Computer Systems, Inc.<br>Copyright &#169; 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>)
      </p>
<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
      at the Pervasive Technology Labs at Indiana University.  For
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      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: 
        </p>
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