SG16 will hold a telecon on Wednesday, October 19th, at 19:30 UTC (timezone conversion).

The agenda is:

The details below are a copy of what was originally included with the agenda for the October 12th meeting.

INCITS has made US NB comments available to its members. I reviewed the list and identified the following as ones that I believe SG16 should establish a position on. There are other comments that are related to papers SG16 has previously discussed, but in those cases, I believe the concerns raised do not require SG16 input.

Due to duplicated comments in the list of US comments, it is possible that the comment identifiers below will change.

US-2: [defns.multibyte]

The notion of an "execution character set" is no longer given prominence in the Draft standard, aside from some notes about its relationship to the concept as defined by C, and clarifying that certain character encodings are unrelated to this character set. This makes it a questionable choice for use in the definition of "multibyte character".

Proposed change:

Change the definition of "multibyte character" to use a character encoding with a more definite specification given by the Standard.

US-38: [format.string.escaped]

The subject subclause describes how characters or strings are "escaped" to be formatted more suitably "for debugging or for logging".

The actual suitability for debugging or for logging depends on the needs of the application, and there is a conflict between formatting for human readability of the textual content and formatting for clarity and fidelity of encoding nuances. Indeed, for the latter, there can still be (for stateful encodings) a conflict between formatting for human visual inspection versus formatting for machine consumption of the output sequence as a C++ string/character literal.

The current design introduces extensions to the API and to the format string syntax that assume that there is one specific default that should be chosen "for debugging or for logging". The reasoning behind the chosen default and the extensibility of the current design does not appear to be sufficiently explored.

Note 1:
An example, for Unicode encodings, of a choice between prioritizing between human readability of the textual content and visual clarity of encoding nuances is in the treatment of characters having Unicode property Grapheme_Extend=Yes. The current design favors visual clarity of encoding nuances by outputing such characters as escape sequences.

Note 2:
For stateful encodings, the lack of return to the initial shift state at the end of the sequence cannot be represented using a C++ string/character literal unless if a prior shift sequence from the initial shift state is rendered via escape sequence(s). It is not clear that scanning forward is generally always an option (nor is it clear that doing so is desirable).

Proposed change:

Narrow the purported scope and affirm the design choices of the default behavior:
Modify "logging" to "technical logging" and spell out the priorities in order in the description (this has the benefit of clearly communicating intention and providing guidance for implementation choices).

  1. The output is intended to be a C++ string/character literal that reproduces the encoded sequence. (This seems to be taken for granted and not made explicit in the current draft.)
  2. Prefer visually distinguishing between different methods of encoding "equivalent" textual content.

Make any adjustments necessary to the API or the format string syntax associated with "escaped" strings to allow for future additions for alternative escaping.

US-64: [uaxid.pattern]

The Unicode org has clarified that the pattern whitespace and pattern syntax rules apply to the lexing and parsing of computer languages.

Proposed change:

Replace with "UAX#31 describes how formal languages such as computer languages should describe and implement their use of whitespace and syntactically significant characters during the processes of lexing and parsing. C++ does not claim conformance with this requirement."

Tom.