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<title>Issue 554: Problem with lwg DR 184 numeric_limits&lt;bool&gt;</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="554"><a href="lwg-closed.html#554">554</a>. Problem with lwg DR 184 numeric_limits&lt;bool&gt;</h3>
<p><b>Section:</b> 17.3.5.3 <a href="https://wg21.link/numeric.special">[numeric.special]</a> <b>Status:</b> <a href="lwg-active.html#NAD">NAD</a>
 <b>Submitter:</b> Howard Hinnant <b>Opened:</b> 2006-01-29 <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#numeric.special">issues</a> in [numeric.special].</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 believe we have a bug in the resolution of:
<a href="lwg-defects.html#184" title="numeric_limits&lt;bool&gt; wording problems (Status: CD1)">184</a><sup><a href="https://cplusplus.github.io/LWG/issue184" title="Latest snapshot">(i)</a></sup>
(WP status).
</p>

<p>
The resolution spells out each member of <code>numeric_limits&lt;bool&gt;</code>.
The part I'm having a little trouble with is:
</p>
<blockquote><pre>
static const bool traps = false;
</pre></blockquote>

<p>
Should this not be implementation defined?  Given:
</p>

<blockquote><pre>
int main()
{
     bool b1 = true;
     bool b2 = false;
     bool b3 = b1/b2;
}
</pre></blockquote>

<p>
If this causes a trap, shouldn't <code>numeric_limits&lt;bool&gt;::traps</code> be
<code>true</code>?
</p>


<p id="res-554"><b>Proposed resolution:</b></p>
<p>
Change 18.2.1.5p3:
</p>

<blockquote><p>
-3- The specialization for <code>bool</code> shall be provided as follows: </p>
<blockquote><pre>
namespace std { 
   template &lt;&gt; class numeric_limits&lt;bool&gt; {
      ...
      static const bool traps = <del>false</del> <ins><i>implementation-defined</i></ins>;
      ...
   };
}
</pre></blockquote>
</blockquote>

<p><i>[
Redmond:  NAD because traps refers to values, not operations.  There is no bool
value that will trap.
]</i></p>







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