Is it viable to defer to Unicode for the definitions of new-line and whitespace?

             Peter

From: SG16 <sg16-bounces@lists.isocpp.org> On Behalf Of Corentin via SG16
Sent: 01 June 2020 13:54
To: SG16 <sg16@lists.isocpp.org>
Cc: Corentin <corentin.jabot@gmail.com>
Subject: [SG16] During lexing, What constitute new lines and whitespaces ?

EXTERNAL MAIL

The standard doesn't specify what the new-line character is.

According to Unicode, the following codepoint sequences should be considered lines terminators

 LF:    Line Feed, U+000A
 VT:    Vertical Tab, U+000B
 FF:    Form Feed, U+000C
 CR:    Carriage Return, U+000D
 CR+LF: CR (U+000D) followed by LF (U+000A)
 NEL:   Next Line, U+0085
 LS:    Line Separator, U+2028
 PS:    Paragraph Separator, U+2029

Similarly, the standard defines "white spaces" loosely as "blanks, horizontal and vertical tabs", however there are more white space characters in unicode https://en.wikipedia.org/wiki/Whitespace_character

What I would like to do:

* Define new-line and white-spaces as grammar term, with an explicit list of codepoint sequences.   

* In phase 2, replace all characters which represent a line termination with Line Feed (which is reverted later for raw string literals). this would notably fix https://wg21.link/cwg1655

* It would also help to mandate that trailing whitespaces are removed in phase 2

Does that make sense to anyone ?