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Re: [SG16] Agenda for the 2021-12-01 SG16 telecon

From: Victor Zverovich <victor.zverovich_at_[hidden]>
Date: Wed, 1 Dec 2021 07:26:03 -0800
> Is there value in specifying it?

Yes, I think there is value in handling this case consistently across
implementations. Option 1 is problematic for width = 2 and not just with
alignment to the end so it looks like 3 is the most sensible one (option 2
is clearly wrong and just there for completeness).


On Tue, Nov 30, 2021 at 10:13 AM Tom Honermann via SG16 <
sg16_at_[hidden]> wrote:

> This is your friendly reminder that this telecon will take place tomorrow.
> If we manage to get through both LWG3639 and P2286R3, we'll resume
> discussion of P2361R4 (Unevaluated strings) and potentially poll forwarding
> it.
> Tom.
> On 11/27/21 7:30 PM, Tom Honermann via SG16 wrote:
> SG16 will hold a telecon on Wednesday, December 1st at 19:30 UTC (timezone
> conversion
> <https://www.timeanddate.com/worldclock/converter.html?iso=20211201T193000&p1=1440&p2=tz_pst&p3=tz_mst&p4=tz_cst&p5=tz_est&p6=tz_cet>
> ).
> The agenda is:
> - LWG3639: Handling of fill character width is underspecified in
> std::format <https://wg21.link/lwg3639>
> - P2286R3: Formatting Ranges <https://wg21.link/p2286r3>
> For LWG3639 <https://wg21.link/lwg3639>, the issue discussion enumerates
> three possible solutions, though others are possible. There is also a
> related wording omission; table [tab.format.align]
> <http://eel.is/c++draft/tab:format.align> doesn't actually specify how
> alignment is achieved for the '<' and '>' options (the wording doesn't
> state to insert fill characters as it does for the '^' option).
> Additionally, further tweaking (and possibly new LWG issues) may be needed
> to address these concerns:
> 1. If the width of the value exceeds the field width, then alignment
> to the end of the available space is not possible.
> [format.string.std]p8 <http://eel.is/c++draft/format.string.std#8>
> should be updated to address this possibility, presumably by noting that
> the content may overflow the available space resulting in misalignment.
> std::format("{:X>1}}, 9999);
> 2. If the estimated width of the fill character is greater than 1,
> then alignment to the end of the available space might not be possible. The
> choice here is whether to under-fill or over-fill the available space. This
> possibility is avoided if fill characters are restricted to characters with
> an estimated width of exactly 1.
> std::format("{:🤡>4}", 123);
> For P2286R3 <https://wg21.link/p2286r3>, LEWG requested
> <https://lists.isocpp.org/sg16/2021/11/2845.php> that SG16 consider the
> ramifications for support of user defined delimiters. We should also
> discuss the "?" specifier proposed to explicitly opt in to quoted and
> escaped formats for std::string, std::string_view, and arrays of char/
> wchar_t.
> Tom.
> --
> SG16 mailing list
> SG16_at_[hidden]
> https://lists.isocpp.org/mailman/listinfo.cgi/sg16

Received on 2021-12-01 09:26:17