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<title>Issue 4191: P1467 changed the return type of pow(complex&lt;float&gt;, int)</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="4191"><a href="lwg-defects.html#4191">4191</a>. P1467 changed the return type of <code>pow(complex&lt;float&gt;, int)</code></h3>
<p><b>Section:</b> 29.4.10 <a href="https://wg21.link/cmplx.over">[cmplx.over]</a> <b>Status:</b> <a href="lwg-active.html#WP">WP</a>
 <b>Submitter:</b> Tim Song <b>Opened:</b> 2025-01-10 <b>Last modified:</b> 2025-02-16</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View all other</b> <a href="lwg-index.html#cmplx.over">issues</a> in [cmplx.over].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#WP">WP</a> status.</p>
<p><b>Discussion:</b></p>
<p>
Before C++20, 29.4.10 <a href="https://wg21.link/cmplx.over">[cmplx.over]</a> says that this produces a <code>complex&lt;double&gt;</code>. 
This was confirmed by LWG <a href="lwg-defects.html#844" title="complex pow return type is ambiguous (Status: CD1)">844</a><sup><a href="https://cplusplus.github.io/LWG/issue844" title="Latest snapshot">(i)</a></sup> and consistent with C99.
<p/>
<a href="https://wg21.link/P1467" title=" Extended floating-point types and standard names">P1467</a> changed the return type to <code>complex&lt;common_type_t&lt;float, int&gt;&gt;</code>, 
which is <code>complex&lt;float&gt;</code>. This is a breaking change that does not appear to have been 
intentional.
</p>

<p><i>[2025-02-07; Reflector poll]</i></p>

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

<p><i>[Hagenberg 2025-02-16; Status changed: Voting &rarr; WP.]</i></p>



<p id="res-4191"><b>Proposed resolution:</b></p>
<p>
This wording is relative to <a href="https://wg21.link/N5001" title=" Working Draft, Programming Languages — C++">N5001</a>.
</p>

<ol>

<li><p>Modify 29.4.10 <a href="https://wg21.link/cmplx.over">[cmplx.over]</a> as indicated:</p>

<blockquote><p>
-3- Function template <code class='backtick'>pow</code> has additional constexpr overloads sufficient to ensure, for a call with one argument of
type <code>complex&lt;T1&gt;</code> and the other argument of type <code class='backtick'>T2</code> or <code>complex&lt;T2&gt;</code>, both arguments 
are effectively cast to <code>complex&lt;common_type_t&lt;T1, <ins>T3</ins><del>T2</del>&gt;&gt;</code><ins>, where 
<code class='backtick'>T3</code> is <code class='backtick'>double</code> if <code class='backtick'>T2</code> is an integer type and <code class='backtick'>T2</code> otherwise</ins>. If <code>common_type_t&lt;T1, <ins>T3</ins><del>T2</del>&gt;</code> 
is not well-formed, then the program is ill-formed.
</p></blockquote>
</li>
</ol>






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