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Subject: Agenda for the 2021-04-28 SG16 telecon
From: Tom Honermann (tom_at_[hidden])
Date: 2021-04-19 09:58:45


SG16 will hold a telecon on Wednesday, April 28th at 19:30 UTC (timezone
conversion
<https://www.timeanddate.com/worldclock/converter.html?iso=20210428T193000&p1=1440&p2=tz_pdt&p3=tz_mdt&p4=tz_cdt&p5=tz_edt&p6=tz_cest>).

The agenda is:

  * P2093R5: Formatted output <https://wg21.link/p2093r5>
  * P2348R0: Whitespaces Wording Revamp
    <https://isocpp.org/files/papers/P2348R0.pdf>

LEWG discussed P2093R5 at their 2021-04-06 telecon and decided to refer
the paper back to SG16 for further discussion.  LEWG meeting minutes are
available here
<https://wiki.edg.com/bin/view/Wg21telecons2021/P2093#Library-Evolution-2021-04-06>;
please review them prior to the telecon.  LEWG reviewed the list of
prior SG16 deferred questions posted to them here
<http://lists.isocpp.org/lib-ext/2021/03/18189.php>. Of those, they
established consensus on an answer for #2 (they agreed not to block
std::print() on a proposal for underlying terminal facilities), but
referred the rest back to us.  My interpretation of their actions is
that LEWG would like a revision of the paper to address these concerns
based on SG16 input (e.g., discuss design options and SG16 consensus or
lack thereof).  We'll therefore focus on these questions at this telecon.

Hubert provided the following very interesting example usage.

std::print("{:%r}\n", std::chrono::system_clock::now().time_since_epoch());

At issue is the encoding used by locale sensitive chrono formatters. 
Search [time.format] <http://eel.is/c++draft/time.format> for "locale"
to find example chrono format specifiers that are locale dependent.  The
example above contains the %r specifier and is locale sensitive because
AM/PM designations may be localized.  In a Chinese locale the desired
translation of "PM" is "下午", but the locale will provide the translation
in the locale encoding.  As specified in P2093R5, if the execution
(literal) encoding is UTF-8, than std::print() will expect the
translation to be provided in UTF-8, but if the locale is not
UTF-8-based (e.g., Big5; perhaps Shift-JIS for the Japanese 午後
translation), then the result is mojibake. This is a good example of how
locale conflates translation and character encoding.

Addressing the above will be our first order of business.  Please
reserve some time to independently think about this problem (ignore
responses to this message for a few days if you need to). I am
explicitly not listing possible approaches to address this concern in
this message so as to avoid adding (further) bias in any specific
direction.  I suspect the answers to the previously deferred SG16
questions will be easier to answer once this concern is resolved.

I do not intend to time limit discussion of P2093R5 as I believe this is
an important matter to resolve.  If we are able to complete discussion
of P2093R5, then we'll discuss P2348R0.

Tom.



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