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<title>Issue 436: are cv-qualified facet types valid facets?</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="436"><a href="lwg-defects.html#436">436</a>. are cv-qualified facet types valid facets?</h3>
<p><b>Section:</b> 28.3.3.1.2.2 <a href="https://wg21.link/locale.facet">[locale.facet]</a> <b>Status:</b> <a href="lwg-active.html#CD1">CD1</a>
 <b>Submitter:</b> Martin Sebor <b>Opened:</b> 2003-10-15 <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#locale.facet">issues</a> in [locale.facet].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#CD1">CD1</a> status.</p>
<p><b>Discussion:</b></p>
<p>
Is "const std::ctype&lt;char>" a valid template argument to has_facet, use_facet,
and the locale template ctor? And if so, does it designate the same Facet as
the non-const "std::ctype&lt;char>?" What about "volatile std::ctype&lt;char>?"
Different implementations behave differently: some fail to compile, others
accept such types but behave inconsistently.
</p>


<p id="res-436"><b>Proposed resolution:</b></p>
<p>Change 22.1.1.1.2, p1 to read:</p>

<p>Template parameters in this clause which are required to be facets
are those named Facet in declarations. A program that passes a type
that is not a facet, or a type that refers to volatile-qualified
facet, as an (explicit or deduced) template parameter to a locale
function expecting a facet, is ill-formed.  A const-qualified facet is
a valid template argument to any locale function that expects a Facet
template parameter.</p>

<p><i>[Kona: changed the last sentence from a footnote to normative
text.]</i></p>






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