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<title>Issue 4232: datapar::resize does not resize</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#WP">WP</a> status.</em></p>
<h3 id="4232"><a href="lwg-defects.html#4232">4232</a>. <code class='backtick'>datapar::resize</code> does not resize</h3>
<p><b>Section:</b> 29.10.4 <a href="https://wg21.link/simd.traits">[simd.traits]</a> <b>Status:</b> <a href="lwg-active.html#WP">WP</a>
 <b>Submitter:</b> Tim Song <b>Opened:</b> 2025-03-24 <b>Last modified:</b> 2025-06-23</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View all issues with</b> <a href="lwg-status.html#WP">WP</a> status.</p>
<p><b>Discussion:</b></p>
<p>
The wording actually requires the size to be left unchanged.
</p>

<p><i>[2025-06-12; Reflector poll]</i></p>

<p>
Set status to Tentatively Ready after seven votes in favour during reflector poll.
</p>

<p><i>[Sofia 2025-06-21; Status changed: Voting &rarr; WP.]</i></p>



<p id="res-4232"><b>Proposed resolution:</b></p>
<p>
This wording is relative to <a href="https://wg21.link/N5008" title=" Working Draft, Programming Languages — C++">N5008</a>.
</p>

<ol>

<li><p>Modify 29.10.4 <a href="https://wg21.link/simd.traits">[simd.traits]</a> as indicated:</p>

<blockquote>
<pre>
template&lt;<i>simd-size-type</i> N, class V&gt; struct resize { using type = <i>see below</i>; };
</pre>
<blockquote>
<p>
[&hellip;]
<p/>
-9- If <code class='backtick'>V</code> is a specialization of <code class='backtick'>basic_simd</code>, let <code class='backtick'>Abi1</code> denote an ABI tag such that 
<code>basic_simd&lt;T, Abi1&gt;::size()</code> equals <code><del>V::size()</del><ins>N</ins></code>. 
If <code class='backtick'>V</code> is a specialization of <code class='backtick'>basic_simd_mask</code>, let <code class='backtick'>Abi1</code> denote an ABI tag such that 
<code>basic_simd_mask&lt;sizeof(T), Abi1&gt;::size()</code> equals <code><del>V::size()</del><ins>N</ins></code>.
</p>
</blockquote>
</blockquote>
</li>

</ol>





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