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    CWG Issue 2636</TITLE>
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<P><EM>This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21
  Core Issues List revision 118b.
  See http://www.open-std.org/jtc1/sc22/wg21/ for the official
  list.</EM></P>
<P>2025-09-28</P>
<HR>
<A NAME="2636"></A><H4>2636.
  
Update Annex E based on Unicode 15.0 UAX #31
</H4>
<B>Section: </B>Clause Annex E&#160; [<A href="https://wg21.link/ub">ub</A>]
 &#160;&#160;&#160;

 <B>Status: </B>C++23
 &#160;&#160;&#160;

 <B>Submitter: </B>Steve Downey
 &#160;&#160;&#160;

 <B>Date: </B>2022-10-20<BR><BR>


<A href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p2720r0.pdf#US64-132">P2720R0 comment
  US&#160;64-132<BR></A>

<P>[Accepted as a DR at the November, 2022 meeting.]</P>

<P>Unicode 15.0 UAX #31 clarified that rule R3 was, in fact, intended
to apply to programming languages.  WG21's prior understanding was
that programming languages are not in scope of that rule.  The
proposed resolution updates E.4 [<A href="https://wg21.link/ub.stmt.stmt">ub.stmt.stmt</A>] to the revised
understanding. See paper P2653R1 (Update Annex E based on Unicode 15.0
UAX 31) for more details.</P>

<P><B>Proposed resolution (approved by CWG 2022-10-21):</B></P>

<P>Change in E.4 [<A href="https://wg21.link/ub.stmt.stmt">ub.stmt.stmt</A>] as follows:</P>

<BLOCKQUOTE>

<P>
UAX #31 describes how <INS>formal</INS> languages <DEL>that use or
interpret patterns of characters, such as regular expressions or
number formats, may describe that syntax with Unicode properties</DEL>
<INS>such as computer languages should describe and implement their
use of whitespace and syntactically significant characters during the
processes of lexing and parsing</INS>.
</P>

<P>
C++ does not <DEL>do this as part of the language, deferring to
library components for such usage of patterns.  This requirement does
not apply to C++</DEL> <INS>claim conformance with this
requirement</INS>.
</P>

</BLOCKQUOTE>

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