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<title>Issue 693: std::bitset::all() missing</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="693"><a href="lwg-defects.html#693">693</a>. <code>std::bitset::all()</code> missing</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#CD1">CD1</a>
 <b>Submitter:</b> Martin Sebor <b>Opened:</b> 2007-06-22 <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#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#CD1">CD1</a> status.</p>
<p><b>Discussion:</b></p>
<p>
The  <code>bitset</code> class template  provides the  member function
<code>any()</code> to determine whether an  object of the type has any
bits  set, and  the member  function <code>none()</code>  to determine
whether all of an object's  bits are clear. However, the template does
not   provide  a   corresponding  function   to  discover   whether  a
<code>bitset</code>  object  has  all  its  bits  set.   While  it  is
possible,  even easy,  to  obtain this  information  by comparing  the
result of <code>count()</code>  with the result of <code>size()</code>
for  equality  (i.e.,  via  <code>b.count()  ==  b.size()</code>)  the
operation  is   less  efficient   than  a  member   function  designed
specifically  for that purpose  could be.   (<code>count()</code> must
count  all non-zero bits  in a  <code>bitset</code> a  word at  a time
while <code>all()</code> could stop counting as soon as it encountered
the first word with a zero bit).
</p>


<p id="res-693"><b>Proposed resolution:</b></p>
<p>
Add a declaration of the new  member function <code>all()</code> to the
defintion of the <code>bitset</code> template in 22.9.2 <a href="https://wg21.link/template.bitset">[template.bitset]</a>, p1,
right above the declaration of <code>any()</code> as shown below:
</p>

<blockquote><pre>
bool operator!=(const bitset&lt;N&gt;&amp; rhs) const;
bool test(size_t pos) const;
<ins>bool all() const;</ins>
bool any() const;
bool none() const;
</pre></blockquote>

<p>
Add a description of the new member function to the end of 22.9.2.3 <a href="https://wg21.link/bitset.members">[bitset.members]</a> with the following text:
</p>
<blockquote><p>
<code>bool all() const;</code>
</p>
<blockquote><p>
<i>Returns</i>: <code>count() == size()</code>.
</p></blockquote>
</blockquote>

<p>
In  addition,   change  the  description   of  <code>any()</code>  and
<code>none()</code>   for  consistency   with   <code>all()</code>  as
follows:
</p>
<blockquote><p>
<code>bool any() const;</code>
</p>
<blockquote>
<p>
<i>Returns</i>: <del><code>true</code> if any bit in <code>*this</code>
is one</del><ins><code>count() != 0</code></ins>.
</p>
</blockquote>
<p>
<code>bool none() const;</code>
</p>
<blockquote>
<p>
<i>Returns</i>: <del><code>true</code> if no bit in <code>*this</code>
is one</del><ins><code>count() == 0</code></ins>.
</p>
</blockquote>
</blockquote>





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