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<title>Concept InputIterator</title>
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<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" lang="en">
<a name="id975397"></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" lang="en">
<a name="id975412"></a><h2>Refinement of</h2>
<div class="itemizedlist"><ul type="disc">
<li><p><a href="Assignable.html" title="Concept Assignable">Assignable</a></p></li>
<li><p><a href="DefaultConstructible.html" title="Concept DefaultConstructible">DefaultConstructible</a></p></li>
<li><p><a href="EqualityComparable.html" title="Concept EqualityComparable">EqualityComparable</a></p></li>
</ul></div>
</div>
<div class="refsect1" lang="en">
<a name="id975441"></a><h2>Associated types</h2>
<div class="itemizedlist"><ul type="disc">
<li>
<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>
<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>
<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" lang="en">
<a name="id975504"></a><h2>Notation</h2>
<div class="variablelist"><dl>
<dt><span class="term">Iter</span></dt>
<dd>A type playing the role of iterator-type in the <a 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" lang="en">
<a name="id975542"></a><h2>Type expressions</h2>
<div class="variablelist"><dl>
<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 href="DefaultConstructible.html" title="Concept DefaultConstructible">DefaultConstructible</a>,  and  a model  of <a 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 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 href="SignedInteger.html" title="Concept SignedInteger">SignedInteger</a>.
                </p></dd>
</dl></div>
</div>
<div class="refsect1" lang="en">
<a name="id975612"></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 &amp;</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" lang="en">
<a name="id975758"></a><h2>Complexity</h2>
<p>
  All iterator operations must take amortized constant time.
  </p>
</div>
<div class="refsect1" lang="en">
<a name="id975765"></a><h2>Models</h2>
<div class="itemizedlist"><ul type="disc"><li><span class="simplelist"><span class="type">std::istream_iterator</span></span></li></ul></div>
</div>
<div class="refsect1" lang="en">
<a name="id975777"></a><h2>See also</h2>
<div class="itemizedlist"><ul type="disc">
<li><p><a href="DefaultConstructible.html" title="Concept DefaultConstructible">DefaultConstructible</a></p></li>
<li><p><a href="EqualityComparable.html" title="Concept EqualityComparable">EqualityComparable</a></p></li>
<li><p><a href="ForwardIterator.html" title="Concept ForwardIterator">ForwardIterator</a></p></li>
<li><p><a href="OutputIterator.html" title="Concept OutputIterator">OutputIterator</a></p></li>
</ul></div>
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