On 22/05/2022 23.40, Hubert Tong wrote:
> On Sun, May 22, 2022 at 5:11 PM Hubert Tong
> <hubert.reinterpretcast_at_[hidden]> wrote:
>>
>> On Sun, May 22, 2022 at 2:24 AM Jens Maurer via SG16
>> <sg16_at_[hidden]> wrote:

>>> It seems we need to check that the C++ understanding of whitespace is
>>> a subset of Pattern_White_Space.
>>
>> It is a subset (exactly the subset within U+0000 to U+007F, inclusive;
>> except U+000D CARRIAGE RETURN is not a member of the basic character
>> set(!)).
>
> Once we have P2348, adding U+000D CARRIAGE RETURN to the basic
> character set should actually be editorial.

I disagree with P2348's idea of carrying various spellings of
new-line through. Even in raw string literals, new-lines are
harmonized to "\n", always, so there is no point in preserving
the spelling of new-line during lexing. We should keep the
existing phrasing that phase 1 replaces end-of-line indicators
(which might be CR-LF) with new-line, which we should clarify to
be U+000A LINE FEED.

> Nothing in the wording as it is now precludes the grammar from having
> characters outside the basic character set be significant to parsing.

Agreed.

> \u000d is already ill-formed outside of string and character literals,
> and it is already in the basic literal character set.

Well, in the status quo, U+000D CARRIAGE RETURN could be part of
"new-line", which certainly appears outside of literals.
I agree that the UCN \u000d is ill-formed outside of literals,
though.

>> Also, whether the requirement means that a language has exactly
>> Pattern_White_Space as its definition for whitespace is in question.

Good question. That means WG21 probably shouldn't act on this
until the promised editorial rewrite of UAX31 is available.

Jens