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| 22 | <div class="spirit-nav"> |
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| 23 | <a accesskey="p" href="InputIterator.html"><img src="images/prev.png" alt="Prev"></a><a accesskey="u" href="concepts/reference.html"><img src="images/up.png" alt="Up"></a><a accesskey="h" href="index.html"><img src="images/home.png" alt="Home"></a><a accesskey="n" href="ForwardIterator.html"><img src="images/next.png" alt="Next"></a> |
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| 24 | </div> |
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| 25 | <div class="refentry" lang="en"> |
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| 26 | <a name="OutputIterator"></a><div class="titlepage"></div> |
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| 27 | <div class="refnamediv"> |
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| 28 | <h2><span class="refentrytitle">Concept OutputIterator</span></h2> |
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| 29 | <p>OutputIterator</p> |
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| 30 | </div> |
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| 31 | <div class="refsect1" lang="en"> |
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| 32 | <a name="id2576510"></a><h2>Description</h2> |
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| 33 | <p>An output iterator is an iterator that can write a sequence of |
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| 34 | values. It is single-pass (old values of the iterator cannot be |
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| 35 | re-used), and write-only.</p> |
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| 36 | <p>An output iterator represents a position in a (possibly infinite) |
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| 37 | sequence. Therefore, the iterator can point into the sequence (returning |
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| 38 | a value when dereferenced and being incrementable), or be off-the-end |
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| 39 | (and not dereferenceable or incrementable).</p> |
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| 40 | </div> |
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| 41 | <div class="refsect1" lang="en"> |
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| 42 | <a name="id2576525"></a><h2>Associated types</h2> |
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| 43 | <div class="itemizedlist"><ul type="disc"> |
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| 44 | <li> |
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| 45 | <p><span class="bold"><strong>value_type</strong></span></p> |
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| 46 | <pre class="literallayout">std::iterator_traits<Iter>::value_type</pre> |
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| 47 | <p>The stated value type of the iterator (should be |
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| 48 | <code class="computeroutput">void</code> for an output iterator that does not model some other |
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| 49 | iterator concept).</p> |
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| 50 | </li> |
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| 51 | <li> |
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| 52 | <p><span class="bold"><strong>difference_type</strong></span></p> |
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| 53 | <pre class="literallayout">std::iterator_traits<Iter>::difference_type</pre> |
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| 54 | <p>The difference type of the iterator</p> |
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| 55 | </li> |
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| 56 | <li> |
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| 57 | <p><span class="bold"><strong>category</strong></span></p> |
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| 58 | <pre class="literallayout">std::iterator_traits<Iter>::iterator_category</pre> |
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| 59 | <p>The category of the iterator</p> |
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| 60 | </li> |
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| 61 | </ul></div> |
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| 62 | </div> |
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| 63 | <div class="refsect1" lang="en"> |
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| 64 | <a name="id2576590"></a><h2>Notation</h2> |
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| 65 | <div class="variablelist"><dl> |
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| 66 | <dt><span class="term">Iter</span></dt> |
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| 67 | <dd>A type playing the role of iterator-type in the <a href="OutputIterator.html" title="Concept OutputIterator">OutputIterator</a> concept.</dd> |
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| 68 | <dt><span class="term">ValueType</span></dt> |
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| 69 | <dd>A type playing the role of value-type in the <a href="OutputIterator.html" title="Concept OutputIterator">OutputIterator</a> concept.</dd> |
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| 70 | <dt> |
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| 71 | <span class="term"><code class="varname">i</code>, </span><span class="term"><code class="varname">j</code></span> |
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| 72 | </dt> |
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| 73 | <dd>Objects of type Iter</dd> |
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| 74 | <dt><span class="term"><code class="varname">x</code></span></dt> |
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| 75 | <dd>Object of type ValueType</dd> |
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| 76 | </dl></div> |
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| 77 | </div> |
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| 78 | <div class="refsect1" lang="en"> |
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| 79 | <a name="id2576644"></a><h2>Type expressions</h2> |
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| 80 | <div class="variablelist"><dl> |
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| 81 | <dt><span class="term"></span></dt> |
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| 82 | <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> |
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| 83 | <dt><span class="term"></span></dt> |
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| 84 | <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> |
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| 85 | <dt><span class="term"></span></dt> |
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| 86 | <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> |
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| 87 | <dt><span class="term"></span></dt> |
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| 88 | <dd><p>The type <span class="type">Iter</span> must be a model of |
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| 89 | <a href="EqualityComparable.html" title="Concept EqualityComparable">EqualityComparable</a>.</p></dd> |
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| 90 | <dt><span class="term">Category tag</span></dt> |
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| 91 | <dd><p><span class="type">category</span> must be |
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| 92 | 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>. |
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| 93 | </p></dd> |
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| 94 | <dt><span class="term">Difference type properties</span></dt> |
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| 95 | <dd><p><span class="type">difference_type</span> must be |
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| 96 | a model of <a href="SignedInteger.html" title="Concept SignedInteger">SignedInteger</a>. |
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| 97 | </p></dd> |
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| 98 | </dl></div> |
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| 99 | </div> |
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| 100 | <div class="refsect1" lang="en"> |
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| 101 | <a name="id2576762"></a><h2>Valid expressions</h2> |
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| 102 | <div class="informaltable"><table class="table"> |
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| 103 | <colgroup> |
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| 104 | <col> |
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| 105 | <col> |
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| 106 | <col> |
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| 107 | <col> |
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| 108 | <col> |
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| 109 | <col> |
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| 110 | </colgroup> |
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| 111 | <thead><tr> |
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| 112 | <th>Name</th> |
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| 113 | <th>Expression</th> |
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| 114 | <th>Type</th> |
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| 115 | <th>Precondition</th> |
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| 116 | <th>Semantics</th> |
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| 117 | <th>Postcondition</th> |
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| 118 | </tr></thead> |
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| 119 | <tbody> |
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| 120 | <tr> |
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| 121 | <td><p>Dereference</p></td> |
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| 122 | <td><p>*i</p></td> |
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| 123 | <td><p></p></td> |
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| 124 | <td><p><code class="computeroutput">i</code> is incrementable (not |
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| 125 | off-the-end)</p></td> |
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| 126 | <td> </td> |
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| 127 | <td> </td> |
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| 128 | </tr> |
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| 129 | <tr> |
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| 130 | <td><p>Dereference and assign</p></td> |
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| 131 | <td><p>*i = x</p></td> |
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| 132 | <td><p></p></td> |
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| 133 | <td><p><code class="computeroutput">i</code> is incrementable (not |
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| 134 | off-the-end)</p></td> |
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| 135 | <td> </td> |
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| 136 | <td><p><code class="computeroutput">*i</code> may not be written to again until it has |
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| 137 | been incremented.</p></td> |
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| 138 | </tr> |
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| 139 | <tr> |
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| 140 | <td><p>Preincrement</p></td> |
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| 141 | <td><p>++i</p></td> |
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| 142 | <td><p><span class="type">Iter &</span></p></td> |
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| 143 | <td><p><code class="computeroutput">i</code> is incrementable (not |
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| 144 | off-the-end)</p></td> |
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| 145 | <td> </td> |
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| 146 | <td> </td> |
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| 147 | </tr> |
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| 148 | <tr> |
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| 149 | <td><p>Postincrement</p></td> |
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| 150 | <td><p>i++</p></td> |
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| 151 | <td><p></p></td> |
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| 152 | <td><p><code class="computeroutput">i</code> is incrementable (not |
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| 153 | off-the-end)</p></td> |
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| 154 | <td><p>Equivalent to <code class="computeroutput">(void)(++i)</code></p></td> |
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| 155 | <td><p><code class="computeroutput">i</code> is dereferenceable or |
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| 156 | off-the-end</p></td> |
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| 157 | </tr> |
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| 158 | <tr> |
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| 159 | <td><p>Postincrement, dereference, and assign</p></td> |
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| 160 | <td><p>*i++ = x</p></td> |
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| 161 | <td><p></p></td> |
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| 162 | <td><p><code class="computeroutput">i</code> is incrementable (not |
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| 163 | off-the-end)</p></td> |
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| 164 | <td><p>Equivalent to <code class="computeroutput">{*i = t; ++i;}</code></p></td> |
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| 165 | <td><p><code class="computeroutput">i</code> is dereferenceable or |
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| 166 | off-the-end</p></td> |
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| 167 | </tr> |
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| 168 | </tbody> |
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| 169 | </table></div> |
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| 170 | </div> |
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| 171 | <div class="refsect1" lang="en"> |
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| 172 | <a name="id2576931"></a><h2>Complexity</h2> |
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| 173 | <p> |
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| 174 | All iterator operations must take amortized constant time. |
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| 175 | </p> |
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| 176 | </div> |
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| 177 | <div class="refsect1" lang="en"> |
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| 178 | <a name="id2576937"></a><h2>Models</h2> |
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| 179 | <div class="itemizedlist"><ul type="disc"> |
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| 180 | <li><span class="simplelist"><span class="type">std::ostream_iterator</span>, <span class="type">...</span></span></li> |
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| 181 | <li><span class="simplelist"><span class="type">std::insert_iterator</span>, <span class="type">...</span></span></li> |
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| 182 | <li><span class="simplelist"><span class="type">std::front_insert_iterator</span>, <span class="type">...</span></span></li> |
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| 183 | <li><span class="simplelist"><span class="type">std::back_insert_iterator</span>, <span class="type">...</span></span></li> |
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| 184 | </ul></div> |
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| 185 | </div> |
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| 186 | <div class="refsect1" lang="en"> |
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| 187 | <a name="id2576987"></a><h2>See also</h2> |
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| 188 | <div class="itemizedlist"><ul type="disc"></ul></div> |
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| 189 | </div> |
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| 190 | </div> |
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| 191 | <table width="100%"><tr> |
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| 192 | <td align="left"></td> |
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| 193 | <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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| 194 | </tr></table> |
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| 195 | <hr> |
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