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<title>Issue 520: Result_of and pointers to data members</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#CD1">CD1</a> status.</em></p>
<h3 id="520"><a href="lwg-defects.html#520">520</a>. Result_of and pointers to data members</h3>
<p><b>Section:</b> 22.10.15 <a href="https://wg21.link/func.bind">[func.bind]</a>, 99 [tr.func.bind] <b>Status:</b> <a href="lwg-active.html#CD1">CD1</a>
 <b>Submitter:</b> Pete Becker <b>Opened:</b> 2005-07-03 <b>Last modified:</b> 2016-01-28</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View all issues with</b> <a href="lwg-status.html#CD1">CD1</a> status.</p>
<p><b>Discussion:</b></p>
<p>
In the original proposal for binders, the return type of bind() when
called with a pointer to member data as it's callable object was
defined to be mem_fn(ptr); when Peter Dimov and I  unified the
descriptions of the TR1 function objects we hoisted the descriptions
of return types into the INVOKE pseudo-function and into result_of.
Unfortunately, we left pointer to member data out of result_of, so
bind doesn't have any specified behavior when called with a pointer
to  member data.
</p>


<p id="res-520"><b>Proposed resolution:</b></p>
<p><i>[
Pete and Peter will provide wording.
]</i></p>


<p>
In 20.5.4 [lib.func.ret] ([tr.func.ret]) p3 add the following bullet after bullet 2:
</p>
<ol>
<li>[&hellip;]</li>
<li>[&hellip;]</li>
<li>If <code>F</code> is a member data pointer type <code>R T::*</code>, <code>type</code>
shall be <code><i>cv</i> R&amp;</code> when <code>T1</code> is <code><i>cv</i> U1&amp;</code>,
<code>R</code> otherwise.</li>
</ol>

<p><i>[
Peter provided wording.
]</i></p>







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