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<title>Issue 11: Bitset minor problems</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#TC1">TC1</a> status.</em></p>
<h3 id="11"><a href="lwg-defects.html#11">11</a>. Bitset minor problems</h3>
<p><b>Section:</b> 22.9.2 <a href="https://wg21.link/template.bitset">[template.bitset]</a> <b>Status:</b> <a href="lwg-active.html#TC1">TC1</a>
 <b>Submitter:</b> Matt Austern <b>Opened:</b> 1998-01-22 <b>Last modified:</b> 2016-08-09</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View other</b> <a href="lwg-index-open.html#template.bitset">active issues</a> in [template.bitset].</p>
<p><b>View all other</b> <a href="lwg-index.html#template.bitset">issues</a> in [template.bitset].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#TC1">TC1</a> status.</p>
<p><b>Discussion:</b></p>
<p>(1) bitset&lt;&gt;::operator[] is mentioned in the class synopsis (23.3.5), but it is
not documented in 23.3.5.2. </p>

<p>(2) The class synopsis only gives a single signature for bitset&lt;&gt;::operator[],
reference operator[](size_t pos). This doesn't make much sense. It ought to be overloaded
on const. reference operator[](size_t pos); bool operator[](size_t pos) const. </p>

<p>(3) Bitset's stream input function (23.3.5.3) ought to skip all whitespace before
trying to extract 0s and 1s. The standard doesn't explicitly say that, though. This should
go in the Effects clause.</p>


<p id="res-11"><b>Proposed resolution:</b></p>
<p>ITEMS 1 AND 2:<br/>
<br/>
In the bitset synopsis (22.9.2 <a href="https://wg21.link/template.bitset">[template.bitset]</a>), 
replace the member function <br/>
<br/>
<code>&nbsp;&nbsp;&nbsp; reference operator[](size_t pos);<br/>
</code><br/>
with the two member functions<br/>
<br/>
<code>&nbsp;&nbsp;&nbsp; bool operator[](size_t pos) const; <br/>
&nbsp;&nbsp;&nbsp; reference operator[](size_t pos); <br/>
</code><br/>
Add the following text at the end of 22.9.2.3 <a href="https://wg21.link/bitset.members">[bitset.members]</a>, 
immediately after paragraph 45:</p>

<blockquote>
  <p><code>bool operator[](size_t pos) const;</code><br/>
  Requires: pos is valid<br/>
  Throws: nothing<br/>
  Returns: <code>test(pos)</code><br/>
  <br/>
  <code>bitset&lt;N&gt;::reference operator[](size_t pos);</code> <br/>
  Requires: pos is valid<br/>
  Throws: nothing<br/>
  Returns: An object of type <code>bitset&lt;N&gt;::reference</code> such that <code>(*this)[pos]
  == this-&gt;test(pos)</code>, and such that <code>(*this)[pos] = val</code> is equivalent to <code>this-&gt;set(pos,
  val);</code></p>
</blockquote>


<p><b>Rationale:</b></p>
<p>The LWG believes Item 3 is not a defect. &quot;Formatted
input&quot; implies the desired semantics. See 31.7.5.3 <a href="https://wg21.link/istream.formatted">[istream.formatted]</a>.
</p>





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