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<title>Issue 2747: Possibly redundant std::move in [alg.foreach]</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++17">C++17</a> status.</em></p>
<h3 id="2747"><a href="lwg-defects.html#2747">2747</a>. Possibly redundant <code>std::move</code> in [alg.foreach]</h3>
<p><b>Section:</b> 26.6.5 <a href="https://wg21.link/alg.foreach">[alg.foreach]</a> <b>Status:</b> <a href="lwg-active.html#C++17">C++17</a>
 <b>Submitter:</b> Jonathan Wakely <b>Opened:</b> 2016-07-15 <b>Last modified:</b> 2017-07-30</p>
<p><b>Priority: </b>0
</p>
<p><b>View other</b> <a href="lwg-index-open.html#alg.foreach">active issues</a> in [alg.foreach].</p>
<p><b>View all other</b> <a href="lwg-index.html#alg.foreach">issues</a> in [alg.foreach].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#C++17">C++17</a> status.</p>
<p><b>Discussion:</b></p>
<p>
26.6.5 <a href="https://wg21.link/alg.foreach">[alg.foreach]</a> p3 says <i>Returns:</i> <code>std::move(f)</code>.
<p/>
 [class.copy] says that since <code>f</code> is a function parameter overload resolution to select the constructor 
for the return value is first performed as if for an rvalue, so the <code>std::move</code> is redundant.
<p/>
It could be argued that it isn't entirely redundant, because it says that implementations can't do something slightly different like return an lvalue reference that is bound to <code>f</code>, which would prevent it being treated as an rvalue. We should discuss it.
</p>
<p><i>[2016-07 Chicago]</i></p>

<p>Monday: P0 - tentatively ready</p>


<p id="res-2747"><b>Proposed resolution:</b></p>
<p>This wording is relative to N4606.</p>

<ol>
<li><p>Change 26.6.5 <a href="https://wg21.link/alg.foreach">[alg.foreach]</a> as indicated:</p>

<blockquote>
<pre>
template&lt;class InputIterator, class Function&gt;
  Function for_each(InputIterator first, InputIterator last, Function f);
</pre>
<blockquote>
<p>
[&hellip;]
<p/>
-3- <i>Returns:</i> <code><del>std::move(</del>f<del>)</del></code>.
<p/>
[&hellip;]
</p>
</blockquote>
</blockquote>
</li>
</ol>





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