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<title>Issue 3362: Strike stop_source's operator!=</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++20">C++20</a> status.</em></p>
<h3 id="3362"><a href="lwg-defects.html#3362">3362</a>. Strike <code>stop_source</code>'s <code>operator!=</code></h3>
<p><b>Section:</b> 32.3.5 <a href="https://wg21.link/stopsource">[stopsource]</a> <b>Status:</b> <a href="lwg-active.html#C++20">C++20</a>
 <b>Submitter:</b> Tim Song <b>Opened:</b> 2020-01-03 <b>Last modified:</b> 2021-02-25</p>
<p><b>Priority: </b>0
</p>
<p><b>View all issues with</b> <a href="lwg-status.html#C++20">C++20</a> status.</p>
<p><b>Discussion:</b></p>
<p>
Just like <code>stop_token</code> (see LWG <a href="lwg-defects.html#3254" title="Strike stop_token's operator!= (Status: C++20)">3254</a><sup><a href="https://cplusplus.github.io/LWG/issue3254" title="Latest snapshot">(i)</a></sup>), <code>stop_source</code> in 32.3.5 <a href="https://wg21.link/stopsource">[stopsource]</a>
declares an <code>operator!=</code> friend that is unnecessary in light of the new core language rules and 
should be struck.
</p>

<p><i>[2020-01-14 Status set to Tentatively Ready after six positive votes on the reflector.]</i></p>



<p id="res-3362"><b>Proposed resolution:</b></p>
<p>This wording is relative to <a href="https://wg21.link/n4842">N4842</a>.</p>

<ol>
<li><p>Modify 32.3.5 <a href="https://wg21.link/stopsource">[stopsource]</a>, class <code>stop_source</code> synopsis, as indicated:</p>

<blockquote>
<pre>
namespace std {
  [&hellip;]

  class stop_source {
  public:
    [&hellip;]

    [[nodiscard]] friend bool
    operator==(const stop_source&amp; lhs, const stop_source&amp; rhs) noexcept;
    <del>[[nodiscard]] friend bool
    operator!=(const stop_source&amp; lhs, const stop_source&amp; rhs) noexcept;</del>
    friend void swap(stop_source&amp; lhs, stop_source&amp; rhs) noexcept;
  };
}
</pre>
</blockquote>

</li>

<li><p>Modify  [stopsource.cmp] and  [stopsource.special] as indicated:</p>

<blockquote>
<p>
<b>32.3.4.3 <ins>Non-member functions</ins><del>Comparisons</del> [stopsource.<ins>nonmembers</ins><del>cmp</del>]</b>
</p>
<pre>
[[nodiscard]] bool operator==(const stop_source&amp; lhs, const stop_source&amp; rhs) noexcept;
</pre>
<blockquote>
<p>
-1- <i>Returns:</i> <code>true</code> if <code>lhs</code> and <code>rhs</code> have ownership of the same stop
state or if both <code>lhs</code> and <code>rhs</code> do not have ownership of a stop state; otherwise <code>false</code>.
</p>
</blockquote>
<pre>
<del>[[nodiscard]] bool operator!=(const stop_source&amp; lhs, const stop_source&amp; rhs) noexcept;</del>
</pre>
<blockquote>
<p>
<del>-2- <i>Returns:</i> <code>!(lhs==rhs)</code>.</del>
</p>
</blockquote>
<p>
<del><b>32.3.4.4 Specialized algorithms [stopsource.special]</b></del>
</p>
<pre>
friend void swap(stop_source&amp; x, stop_source&amp; y) noexcept;
</pre>
<blockquote>
<p>
-1- <i>Effects:</i> Equivalent to: <code>x.swap(y)</code>.
</p>
</blockquote>
</blockquote>

</li>
</ol>





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