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<title>Issue 981: Unordered container requirements should add  initializer_list support</title>
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<p><em>This page is a snapshot from the LWG issues list, see the <a href="lwg-active.html">Library Active Issues List</a> for more information and the meaning of <a href="lwg-active.html#C++11">C++11</a> status.</em></p>
<h3 id="981"><a href="lwg-defects.html#981">981</a>. Unordered container requirements should add  <code>initializer_list</code> support</h3>
<p><b>Section:</b> 23.2.8 <a href="https://wg21.link/unord.req">[unord.req]</a> <b>Status:</b> <a href="lwg-active.html#C++11">C++11</a>
 <b>Submitter:</b> Daniel Kr&uuml;gler <b>Opened:</b> 2009-02-08 <b>Last modified:</b> 2016-01-28</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View other</b> <a href="lwg-index-open.html#unord.req">active issues</a> in [unord.req].</p>
<p><b>View all other</b> <a href="lwg-index.html#unord.req">issues</a> in [unord.req].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#C++11">C++11</a> status.</p>
<p><b>Discussion:</b></p>
<p>
Refering to
<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2800.pdf">N2800</a>
all container requirements tables (including those for
associative containers) provide useful member function overloads
accepting <code>std::initializer_list</code> as argument, the only exception is
Table 87. There seems to be no reason for not providing them, because 23.5 <a href="https://wg21.link/unord">[unord]</a>
is already <code>initializer_list</code>-aware. For the sake of 
library interface consistency and user-expectations corresponding 
overloads should be added to the table requirements of unordered 
containers as well.
</p>

<p><i>[
Batavia (2009-05):
]</i></p>

<blockquote>
<p>
We agree with the proposed resolution.
</p>
<p>
Move to Tentatively Ready.
</p>
</blockquote>


<p id="res-981"><b>Proposed resolution:</b></p>

<p>
In 23.2.8 <a href="https://wg21.link/unord.req">[unord.req]</a>/9 insert:
</p>

<blockquote><p>
... <code>[q1, q2)</code> is a valid range in <code>a</code>, <ins><code>il</code>
designates an object of type <code>initializer_list&lt;value_type&gt;</code>, </ins><code>t</code> is a value of type
<code>X::value_type</code>, ...
</p></blockquote>

<p>
In 23.2.8 <a href="https://wg21.link/unord.req">[unord.req]</a>, Table 87 insert:
</p>

<blockquote>
<table border="1">
<caption>Table 87 - Unordered associative container requirements (in addition to container)</caption>
<tr>
<th>Expression</th> <th>Return type</th> <th>Assertion/note<br/>pre-/post-condition</th> <th>Complexity</th>
</tr>
<tr>
<td><code>X(i, j)<br/>X a(i, j)</code></td> <td><code>X</code></td> <td>...</td> <td>...</td>
</tr>
<tr>
<td><ins><code>X(il)</code></ins></td> <td><ins><code>X</code></ins></td> 
<td><ins>Same as <code>X(il.begin(), il.end())</code>.</ins></td> 
<td><ins>Same as <code>X(il.begin(), il.end())</code>.</ins></td>
</tr>
<tr>
<td>...</td> <td>...</td> <td>...</td> <td>...</td>
</tr>
<tr>
<td><code>a = b</code></td> <td><code>X</code></td> <td>...</td> <td>...</td>
</tr>
<tr>
<td><ins><code>a = il</code></ins></td> <td><ins><code>X&amp;</code></ins></td> 
<td><ins><code>a = X(il); return *this;</code></ins></td> 
<td><ins>Same as <code>a = X(il)</code>.</ins></td>
</tr>
<tr>
<td>...</td> <td>...</td> <td>...</td> <td>...</td>
</tr>
<tr>
<td><code>a.insert(i, j)</code></td> <td><code>void</code></td> <td>...</td> <td>...</td>
</tr>
<tr>
<td><ins><code>a.insert(il)</code></ins></td> <td><ins><code>void</code></ins></td> 
<td><ins>Same as <code>a.insert(il.begin(), il.end())</code>.</ins></td> 
<td><ins>Same as <code>a.insert(il.begin(), il.end())</code>.</ins></td>
</tr>
</table>
</blockquote>






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