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  26 <a name="OutputIterator"></a><div class="titlepage"></div>
  27 <div class="refnamediv">
  28 <h2><span class="refentrytitle">Concept OutputIterator</span></h2>
  29 <p>OutputIterator</p>
  30 </div>
  31 <div class="refsect1">
  32 <a name="id1126732"></a><h2>Description</h2>
  33 <p>An output iterator is an iterator that can write a sequence of
  34   values.  It is single-pass (old values of the iterator cannot be
  35   re-used), and write-only.</p>
  36 <p>An output iterator represents a position in a (possibly infinite)
  37   sequence.  Therefore, the iterator can point into the sequence (returning
  38   a value when dereferenced and being incrementable), or be off-the-end
  39   (and not dereferenceable or incrementable).</p>
  40 </div>
  41 <div class="refsect1">
  42 <a name="id1126750"></a><h2>Associated types</h2>
  43 <div class="itemizedlist"><ul class="itemizedlist" type="disc">
  44 <li class="listitem">
  45 <p><span class="bold"><strong>value_type</strong></span></p>
  46 <pre class="literallayout">std::iterator_traits&lt;Iter&gt;::value_type</pre>
  47 <p>The stated value type of the iterator (should be
  48     <code class="computeroutput">void</code> for an output iterator that does not model some other
  49     iterator concept).</p>
  50 </li>
  51 <li class="listitem">
  52 <p><span class="bold"><strong>difference_type</strong></span></p>
  53 <pre class="literallayout">std::iterator_traits&lt;Iter&gt;::difference_type</pre>
  54 <p>The difference type of the iterator</p>
  55 </li>
  56 <li class="listitem">
  57 <p><span class="bold"><strong>category</strong></span></p>
  58 <pre class="literallayout">std::iterator_traits&lt;Iter&gt;::iterator_category</pre>
  59 <p>The category of the iterator</p>
  60 </li>
  61 </ul></div>
  62 </div>
  63 <div class="refsect1">
  64 <a name="id1126815"></a><h2>Notation</h2>
  65 <div class="variablelist"><dl>
  66 <dt><span class="term">Iter</span></dt>
  67 <dd>A type playing the role of iterator-type in the <a class="link" href="OutputIterator.html" title="Concept OutputIterator">OutputIterator</a> concept.</dd>
  68 <dt><span class="term">ValueType</span></dt>
  69 <dd>A type playing the role of value-type in the <a class="link" href="OutputIterator.html" title="Concept OutputIterator">OutputIterator</a> concept.</dd>
  70 <dt>
  71 <span class="term"><code class="varname">i</code>, </span><span class="term"><code class="varname">j</code></span>
  72 </dt>
  73 <dd>Objects of type Iter</dd>
  74 <dt><span class="term"><code class="varname">x</code></span></dt>
  75 <dd>Object of type ValueType</dd>
  76 </dl></div>
  77 </div>
  78 <div class="refsect1">
  79 <a name="id1126867"></a><h2>Type expressions</h2>
  80 <div class="variablelist"><dl>
  81 <dt><span class="term"></span></dt>
  82 <dd><p>The type <span class="type">Iter</span> must be a model of <a class="link" href="Assignable.html" title="Concept Assignable">Assignable</a>.</p></dd>
  83 <dt><span class="term"></span></dt>
  84 <dd><p>The type <span class="type">ValueType</span> must be a model of <a class="link" href="Assignable.html" title="Concept Assignable">Assignable</a>.</p></dd>
  85 <dt><span class="term"></span></dt>
  86 <dd><p>The type <span class="type">Iter</span> must be a model of <a class="link" href="DefaultConstructible.html" title="Concept DefaultConstructible">DefaultConstructible</a>.</p></dd>
  87 <dt><span class="term"></span></dt>
  88 <dd><p>The type <span class="type">Iter</span> must be a model of
  89   <a class="link" href="EqualityComparable.html" title="Concept EqualityComparable">EqualityComparable</a>.</p></dd>
  90 <dt><span class="term">Category tag</span></dt>
  91 <dd><p><span class="type">category</span> must be
  92                   derived from <span class="type">std::output_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>.
  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 class="link" href="SignedInteger.html" title="Concept SignedInteger">SignedInteger</a>.
  97                 </p></dd>
  98 </dl></div>
  99 </div>
 100 <div class="refsect1">
 101 <a name="id1126985"></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></p></td>
 124 <td><p><code class="computeroutput">i</code> is incrementable (not
 125     off-the-end)</p></td>
 126 <td>&#160;</td>
 127 <td>&#160;</td>
 128 </tr>
 129 <tr>
 130 <td><p>Dereference and assign</p></td>
 131 <td><p>*i = x</p></td>
 132 <td><p></p></td>
 133 <td><p><code class="computeroutput">i</code> is incrementable (not
 134     off-the-end)</p></td>
 135 <td>&#160;</td>
 136 <td><p><code class="computeroutput">*i</code> may not be written to again until it has
 137     been incremented.</p></td>
 138 </tr>
 139 <tr>
 140 <td><p>Preincrement</p></td>
 141 <td><p>++i</p></td>
 142 <td><p><span class="type">Iter &amp;</span></p></td>
 143 <td><p><code class="computeroutput">i</code> is incrementable (not
 144     off-the-end)</p></td>
 145 <td>&#160;</td>
 146 <td>&#160;</td>
 147 </tr>
 148 <tr>
 149 <td><p>Postincrement</p></td>
 150 <td><p>i++</p></td>
 151 <td><p></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">(void)(++i)</code></p></td>
 155 <td><p><code class="computeroutput">i</code> is dereferenceable or
 156     off-the-end</p></td>
 157 </tr>
 158 <tr>
 159 <td><p>Postincrement, dereference, and assign</p></td>
 160 <td><p>*i++ = x</p></td>
 161 <td><p></p></td>
 162 <td><p><code class="computeroutput">i</code> is incrementable (not
 163     off-the-end)</p></td>
 164 <td><p>Equivalent to <code class="computeroutput">{*i = t; ++i;}</code></p></td>
 165 <td><p><code class="computeroutput">i</code> is dereferenceable or
 166     off-the-end</p></td>
 167 </tr>
 168 </tbody>
 169 </table></div>
 170 </div>
 171 <div class="refsect1">
 172 <a name="id1127152"></a><h2>Complexity</h2>
 173 <p>
 174   All iterator operations must take amortized constant time.
 175   </p>
 176 </div>
 177 <div class="refsect1">
 178 <a name="id1127158"></a><h2>Models</h2>
 179 <div class="itemizedlist"><ul class="itemizedlist" type="disc">
 180 <li class="listitem"><span class="simplelist"><span class="type">std::ostream_iterator</span>, <span class="type">...</span></span></li>
 181 <li class="listitem"><span class="simplelist"><span class="type">std::insert_iterator</span>, <span class="type">...</span></span></li>
 182 <li class="listitem"><span class="simplelist"><span class="type">std::front_insert_iterator</span>, <span class="type">...</span></span></li>
 183 <li class="listitem"><span class="simplelist"><span class="type">std::back_insert_iterator</span>, <span class="type">...</span></span></li>
 184 </ul></div>
 185 </div>
 186 </div>
 187 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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