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Re: Agenda for the 2022-07-13 SG16 telecon; no official meeting

From: Jens Maurer <Jens.Maurer_at_[hidden]>
Date: Sat, 9 Jul 2022 21:02:58 +0200
On 09/07/2022 18.25, Corentin Jabot via SG16 wrote:
> Hey Tom.
> If you are *really* bored, I guess you could take a gander at
> https://isocpp.org/files/papers/P2620R0.pdf <https://isocpp.org/files/papers/P2620R0.pdf>

This feels thoroughly confused.

Quote from the paper:

"This is by no mean a major issue in C++, as we don’t put restrictions
on universal-character-names (unlike C)"

Quote from the standard:

"If a universal-character-name outside the c-char-sequence, s-char-sequence, or r-char-sequence
of a character-literal or string-literal (in either case, including within a user-defined-literal) corresponds
to a control character or to a character in the basic character set, the program is ill-formed."

So, there are restrictions in C++ as well.

If the comparison with C wants to highlight the UCN vs. char/string-literal
treatment, it should say so.

Are there places other than identifiers where we can have UCNs
outside of char/string literals? If not, maybe we should massage
the grammar definition of _identifier_ instead of persisting
the handwaving in lex.phases p4.

> https://isocpp.org/files/papers/P2621R0.pdf <https://isocpp.org/files/papers/P2621R0.pdf>

Should this go to SG12, because it discusses undefined behavior?

> * Thinking about tailoring, unicode/cldr locales, localized numbers and dates formatting. Personally I think this is out of scope for 26 and I'm kinda hoping libicu 4x matures.
> But there are questions worth asking. Namely can C++ mandate a dependency on a lib like icu/icu4x, share a common implementation for all vendors, or are we not concerned about the implementation burden of that? Because I am. I think a locale object compliant with unicode is necessary, but if implementers can't take dependencies, an implementation of the cldr seems... asking too much.

In general, I think we can't mandate the dependency on a particular
third-party (non-ISO standardized) library, but we can certainly
standardize an interface that makes it easy to use a specific
third-party library to implement that interface.

But I'd really like to see a roadmap of proposed modern C++-style
interfaces before buying into anything at all.

> I'm already not really comfortable with the implementation burden for non tailored things (and at the same time unwilling to make the design amenable to ICU).

What does "non-tailored" mean?

> * If you folks think text processing would need some rope-like structure, I'm not sure it's text related but... I guess you could talk about that!
> * Some unicode algorithms are unbounded, and may require allocation. A small_vector would help specification,

Why would it help with the specification?

> but again that doesn't seem very in scope of this group.
> * We need *some* unicode properties, I'm not sure which to be honest. My current intent is to only provide things that would be generally useful outside of the algorithms that are otherwise provided.
> You could look at this swift paper https://github.com/apple/swift-evolution/blob/main/proposals/0211-unicode-scalar-properties.md <https://github.com/apple/swift-evolution/blob/main/proposals/0211-unicode-scalar-properties.md>


Received on 2022-07-09 19:03:05