C++ Logo


Advanced search

Subject: Re: During lexing, What constitute new lines and whitespaces ?
From: Peter Brett (pbrett_at_[hidden])
Date: 2020-06-01 10:04:07

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


From: SG16 <sg16-bounces_at_[hidden]> On Behalf Of Corentin via SG16
Sent: 01 June 2020 13:54
To: SG16 <sg16_at_[hidden]>
Cc: Corentin <corentin.jabot_at_[hidden]>
Subject: [SG16] During lexing, What constitute new lines and whitespaces ?


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

Does that make sense to anyone ?

SG16 list run by sg16-owner@lists.isocpp.org