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<title>Concept OutputIterator</title>
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<div class="refentry" lang="en">
<a name="OutputIterator"></a><div class="titlepage"></div>
<div class="refnamediv">
<h2><span class="refentrytitle">Concept OutputIterator</span></h2>
<p>OutputIterator</p>
</div>
<div class="refsect1" lang="en">
<a name="id2576510"></a><h2>Description</h2>
<p>An output iterator is an iterator that can write a sequence of
values. It is single-pass (old values of the iterator cannot be
re-used), and write-only.</p>
<p>An output iterator represents a position in a (possibly infinite)
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="id2576525"></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<Iter>::value_type</pre>
<p>The stated value type of the iterator (should be
<code class="computeroutput">void</code> for an output iterator that does not model some other
iterator concept).</p>
</li>
<li>
<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>
<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" lang="en">
<a name="id2576590"></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="OutputIterator.html" title="Concept OutputIterator">OutputIterator</a> concept.</dd>
<dt><span class="term">ValueType</span></dt>
<dd>A type playing the role of value-type in the <a href="OutputIterator.html" title="Concept OutputIterator">OutputIterator</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 ValueType</dd>
</dl></div>
</div>
<div class="refsect1" lang="en">
<a name="id2576644"></a><h2>Type expressions</h2>
<div class="variablelist"><dl>
<dt><span class="term"></span></dt>
<dd><p>The type <span class="type">Iter</span> must be a model of <a href="Assignable.html" title="Concept Assignable">Assignable</a>.</p></dd>
<dt><span class="term"></span></dt>
<dd><p>The type <span class="type">ValueType</span> must be a model of <a href="Assignable.html" title="Concept Assignable">Assignable</a>.</p></dd>
<dt><span class="term"></span></dt>
<dd><p>The type <span class="type">Iter</span> must be a model of <a href="DefaultConstructible.html" title="Concept DefaultConstructible">DefaultConstructible</a>.</p></dd>
<dt><span class="term"></span></dt>
<dd><p>The type <span class="type">Iter</span> must be a model of
<a href="EqualityComparable.html" title="Concept EqualityComparable">EqualityComparable</a>.</p></dd>
<dt><span class="term">Category tag</span></dt>
<dd><p><span class="type">category</span> must be
derived from <span class="type">std::output_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">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="id2576762"></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></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>Dereference and assign</p></td>
<td><p>*i = x</p></td>
<td><p></p></td>
<td><p><code class="computeroutput">i</code> is incrementable (not
off-the-end)</p></td>
<td> </td>
<td><p><code class="computeroutput">*i</code> may not be written to again until it has
been incremented.</p></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, dereference, and assign</p></td>
<td><p>*i++ = x</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">{*i = t; ++i;}</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="id2576931"></a><h2>Complexity</h2>
<p>
All iterator operations must take amortized constant time.
</p>
</div>
<div class="refsect1" lang="en">
<a name="id2576937"></a><h2>Models</h2>
<div class="itemizedlist"><ul type="disc">
<li><span class="simplelist"><span class="type">std::ostream_iterator</span>, <span class="type">...</span></span></li>
<li><span class="simplelist"><span class="type">std::insert_iterator</span>, <span class="type">...</span></span></li>
<li><span class="simplelist"><span class="type">std::front_insert_iterator</span>, <span class="type">...</span></span></li>
<li><span class="simplelist"><span class="type">std::back_insert_iterator</span>, <span class="type">...</span></span></li>
</ul></div>
</div>
<div class="refsect1" lang="en">
<a name="id2576987"></a><h2>See also</h2>
<div class="itemizedlist"><ul type="disc"></ul></div>
</div>
</div>
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<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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