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<title>Issue 680: move_iterator operator-&gt; return</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="680"><a href="lwg-defects.html#680">680</a>. move_iterator <code>operator-&gt;</code> return</h3>
<p><b>Section:</b> 24.5.4.2 <a href="https://wg21.link/move.iterator">[move.iterator]</a> <b>Status:</b> <a href="lwg-active.html#CD1">CD1</a>
 <b>Submitter:</b> Howard Hinnant <b>Opened:</b> 2007-06-11 <b>Last modified:</b> 2016-01-28</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View other</b> <a href="lwg-index-open.html#move.iterator">active issues</a> in [move.iterator].</p>
<p><b>View all other</b> <a href="lwg-index.html#move.iterator">issues</a> in [move.iterator].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#CD1">CD1</a> status.</p>
<p><b>Discussion:</b></p>
<p>
<code>move_iterator</code>'s <code>operator-&gt;</code> return type <code>pointer</code>
does not consistently match the type which is returned in the description
in  [move.iter.op.ref].
</p>

<blockquote><pre>
template &lt;class Iterator&gt;
class move_iterator {
public:
    ...
    typedef typename iterator_traits&lt;Iterator&gt;::pointer pointer;
    ...
    pointer operator-&gt;() const {return current;}
    ...
private: 
    Iterator current; // exposition only
};
</pre></blockquote>

<p>
There are two possible fixes.
</p>

<ol>
<li><code>pointer operator-&gt;() const {return &amp;*current;}</code></li>
<li><code>typedef Iterator pointer;</code></li>
</ol>

<p>
The first solution is the one chosen by <code>reverse_iterator</code>.  A potential
disadvantage of this is it may not work well with iterators which return a
proxy on dereference and that proxy has overloaded <code>operator&amp;()</code>.  Proxy
references often need to overloaad <code>operator&amp;()</code> to return a proxy
pointer.  That proxy pointer may or may not be the same type as the iterator's
<code>pointer</code> type.
</p>

<p>
By simply returning the <code>Iterator</code> and taking advantage of the fact that
the language forwards calls to <code>operator-&gt;</code> automatically until it
finds a non-class type, the second solution avoids the issue of an overloaded
<code>operator&amp;()</code> entirely.
</p>


<p id="res-680"><b>Proposed resolution:</b></p>
<p>
Change the synopsis in 24.5.4.2 <a href="https://wg21.link/move.iterator">[move.iterator]</a>:
</p>

<blockquote><pre>
typedef <del>typename iterator_traits&lt;</del>Iterator<del>&gt;::pointer</del> pointer;
</pre></blockquote>






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