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<title>Issue 3108: istreambuf_iterator::proxy::operator* should be const</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#New">New</a> status.</em></p>
<h3 id="3108"><a href="lwg-active.html#3108">3108</a>. <code>istreambuf_iterator::proxy::operator*</code> should be <code>const</code></h3>
<p><b>Section:</b> 24.6.4.2 <a href="https://wg21.link/istreambuf.iterator.proxy">[istreambuf.iterator.proxy]</a> <b>Status:</b> <a href="lwg-active.html#New">New</a>
 <b>Submitter:</b> Billy O'Neal III <b>Opened:</b> 2018-04-26 <b>Last modified:</b> 2020-09-06</p>
<p><b>Priority: </b>3
</p>
<p><b>View all issues with</b> <a href="lwg-status.html#New">New</a> status.</p>
<p><b>Discussion:</b></p>
<p>
<code>operator*</code> on iterators is usually intended to be <code>const</code>; see 24.3.5.3 <a href="https://wg21.link/input.iterators">[input.iterators]</a> 
Table 87, <code>*a</code>, where <code>a</code> is of type <code>X</code> or <code>const X</code>. (Technically, <code>proxy</code> 
is implementing the <code>*r++</code> requirement in this table, and <code>r</code> doesn't imply a const iterator, 
but there's no reason for the iterator's <code>operator*</code> to differ from the proxy)
</p>

<p><i>[2018-06-18 after reflector discussion]</i></p>

<p>Priority set to 3</p>


<p id="res-3108"><b>Proposed resolution:</b></p>
<p>
This wording is relative to <a href="https://wg21.link/n4741">N4741</a>.
</p>

<ol>
<li>
<p>Edit 24.6.4.2 <a href="https://wg21.link/istreambuf.iterator.proxy">[istreambuf.iterator.proxy]</a> as indicated:</p>
<blockquote>
<pre>
namespace std {
  template&lt;class charT, class traits = char_traits&lt;charT&gt;&gt;
  class istreambuf_iterator&lt;charT, traits&gt;::proxy { <i>// exposition only</i>
    charT keep_;
    basic_streambuf&lt;charT,traits&gt;* sbuf_;
    proxy(charT c, basic_streambuf&lt;charT,traits&gt;* sbuf)
      : keep_(c), sbuf_(sbuf) { }
    public:
      charT operator*() <ins>const</ins> { return keep_; }
  };
}
</pre>
</blockquote>
</li>
</ol>





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