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<title>Issue 236: ctype&lt;char&gt;::is() member modifies facet</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#Dup">Dup</a> status.</em></p>
<h3 id="236"><a href="lwg-closed.html#236">236</a>. ctype&lt;char&gt;::is() member modifies facet</h3>
<p><b>Section:</b> 28.3.4.2.4.3 <a href="https://wg21.link/facet.ctype.char.members">[facet.ctype.char.members]</a> <b>Status:</b> <a href="lwg-active.html#Dup">Dup</a>
 <b>Submitter:</b> Dietmar K&uuml;hl <b>Opened:</b> 2000-04-24 <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#facet.ctype.char.members">issues</a> in [facet.ctype.char.members].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#Dup">Dup</a> status.</p>
<p><b>Duplicate of:</b> <a href="lwg-defects.html#28" title="Ctype&lt;char&gt;is ambiguous (Status: TC1)">28</a></p>
<p><b>Discussion:</b></p>
<p>The description of the <code>is()</code> member in paragraph 4 of 28.3.4.2.4.3 <a href="https://wg21.link/facet.ctype.char.members">[facet.ctype.char.members]</a> is broken: According to this description, the
second form of the <code>is()</code> method modifies the masks in the
<code>ctype</code> object. The correct semantics if, of course, to obtain
an array of masks. The corresponding method in the general case,
ie. the <code>do_is()</code> method as described in 28.3.4.2.2.3 <a href="https://wg21.link/locale.ctype.virtuals">[locale.ctype.virtuals]</a> paragraph 1 does the right thing.</p>


<p id="res-236"><b>Proposed resolution:</b></p>
  <p>Change paragraph 4 from</p>
    <blockquote><p>
    The second form, for all *p in the range [low, high), assigns
    vec[p-low] to table()[(unsigned char)*p].
    </p></blockquote>
  <p>to become</p>
    <blockquote><p>
    The second form, for all *p in the range [low, high), assigns
    table()[(unsigned char)*p] to vec[p-low].
  </p></blockquote>


<p><b>Rationale:</b></p>





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