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<title>Issue 903: back_insert_iterator issue</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#NAD">NAD</a> status.</em></p>
<h3 id="903"><a href="lwg-closed.html#903">903</a>. <code>back_insert_iterator</code> issue</h3>
<p><b>Section:</b> 24.5.2.2 <a href="https://wg21.link/back.insert.iterator">[back.insert.iterator]</a> <b>Status:</b> <a href="lwg-active.html#NAD">NAD</a>
 <b>Submitter:</b> Dave Abrahams <b>Opened:</b> 2008-09-19 <b>Last modified:</b> 2016-01-28</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View all other</b> <a href="lwg-index.html#back.insert.iterator">issues</a> in [back.insert.iterator].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#NAD">NAD</a> status.</p>
<p><b>Discussion:</b></p>
<p>
I just noticed this; don't know how far the problem(?) extends or
whether it's new or existing: <code>back_insert_iterator</code>'s <code>operator*</code> is not
<code>const</code>, so you can't dereference a <code>const</code> one.
</p>

<p><i>[
Post Summit Daniel adds:
]</i></p>


<blockquote>
<p>
If done, this change should be applied for <code>front_insert_iterator</code>,
<code>insert_iterator</code>, <code>ostream_iterator</code>, and <code>ostreambuf_iterator</code> as well.
</p>
</blockquote>

<p><i>[
Batavia (2009-05):
]</i></p>

<blockquote>
<p>
Alisdair notes that these all are output iterators.
Howard points out that <code>++*i</code>
would no longer work if we made this change.
</p>
<p>
Move to NAD.
</p>
</blockquote>

<p><i>[
2009-05-25 Daniel adds:
]</i></p>


<ol>
<li>
If <a href="lwg-closed.html#1009" title="InputIterator post-increment dangerous (Status: NAD)">1009</a><sup><a href="https://cplusplus.github.io/LWG/issue1009" title="Latest snapshot">(i)</a></sup> is accepted, <code>OutputIterator</code> does no longer support post increment.
</li>
<li>
To support backward compatibility a second overload of <code>operator*</code>
can be added.
Note that the <code>HasDereference</code> concept (and the <code>HasDereference</code> part of concept
<code>Iterator</code>) was specifically refactored to cope with optional const
qualification and
to properly reflect the dual nature of built-in <code>operator*</code> as of
12.6 <a href="https://wg21.link/over.literal">[over.literal]</a>/6.
</li>
</ol>


<p id="res-903"><b>Proposed resolution:</b></p>





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