On 5/14/22 8:17 AM, Corentin Jabot wrote:
> Hey.
> Thanks for the work Barry.
>
> I'm still concerned how long are we still going to keep using the term
> character incorrectly and in context in which its meaning is ambiguous?

Chair hat on: We did discuss this usage during the last telecon
<https://github.com/sg16-unicode/sg16-meetings#may-11th-2022> and
consensus was for this direction though I have no doubt that stronger
consensus could be found with adoption of new terms.

Chair hat off ...

I don't agree that this wording uses "character" incorrectly, but I do
agree that the use here is as ambiguous as usage elsewhere throughout
the standard.

If we want to clean up our use of "character" (and I think we would all
like us to), then I think we need a paper that analyzes how it is
currently used and how many terms are needed to replace it. We could
then identify terms to fit to those uses. Unfortunately, such terms will
likely have to be distinct from what ISO/IEC 10646 provides since many
of those terms are defined in Unicode specific terms.

> Do we have precedence for the use of the term state-transition? (it's
> not an industry term to the best of my knowledge).
I'm not aware of any other uses of this term in the standard. I'll defer
to Hubert whether "state-transition" is an acceptable term of art or
whether there is another term that would be preferred.
>
> In all, I'm afraid i had a preference for the original "unspecified"
> wording, as it's now still unspecified in practice (there is a
> recommended practice without implementation experience, which doesn't
> seem to be much better), and it's using terms that are both imprecise
> and at the same time force implementer hands in
> undesirable implementations.

The recommended practice is only applicable to implementors that support
stateful encodings and was requested by the one participating
implementor that is most likely to be impacted by such encodings. I
don't see anyone's hands being forced. Note that the entire relevant
paragraph is:

  * Otherwise, if /X/ encodes a state transition, the effect on /E/ and
    further decoding of /S/ is unspecified./
    Recommended Practice/: a state transition should be represented in
    /E/ such that the original code unit sequence of /S/ can be
    reconstructed.

> ie, it is not clear to me that preserving shift state in the
> escaped string is a requirement or something implementers will want to
> do in all cases, and in particular, I would expect an escaped strings
> to be the same regardless of the encoding in a high quality implementation

While I tend to agree with your characteristic of a high-quality
implementation, "characters" that contribute solely to change in state
are particular to stateful encodings, so not generally applicable. If we
didn't specify weaker requirements for them, then I would expect them to
fall into the implementation-defined set of non-printable characters and
be rendered as \u{xx} sequences.

Tom.

>
> (I understand that LWG already decided on that (sorry for not
> following) so, it might land on my pile of NB comments)
>
> Thanks,
>
> Corentin
>
> On Sat, May 14, 2022 at 4:48 AM Hubert Tong via SG16
> <sg16_at_[hidden]> wrote:
>
> On Fri, May 13, 2022 at 8:55 PM Tom Honermann via SG16
> <sg16_at_[hidden]> wrote:
>
> Thanks for the update, Barry. No concerns from me!
>
>
> Thanks for the heads up, Barry. Looks okay to me too.
>
>
> Tom.
>
>> On May 13, 2022, at 8:04 PM, Barry Revzin
>> <barry.revzin_at_[hidden]> wrote:
>>
>> 
>> Thank you for making all these iterations!
>>
>> LWG re-affirmed this paper today, making one change. The
>> wording you all provided me had a note:
>>
>> [ *Note*: the intent is that a state transition be
>> represented in `$E$` such that the original code unit
>> sequence of `$S$` can be reconstructed -*end note* ]
>>
>> which LWG wanted to elevate into recommended practice:
>>
>> *Recommended Practice*: a state transition should be
>> represented in `$E$` such that the original code unit
>> sequence of `$S$` can be reconstructed.
>>
>> Same words, just slightly more intentional about the intent.
>> I hope that's okay with everybody. (dif:
>> https://github.com/brevzin/cpp_proposals/commit/fc263d0be55e189a6f98996a7cb06f2f87f82bfd,
>> rendered:
>> https://brevzin.github.io/cpp_proposals/2286_fmt_ranges/p2286r8.html#pnum_21)
>>
>> Thanks again,
>>
>> Barry
>>
>> On Thu, May 12, 2022 at 8:56 AM Tom Honermann
>> <tom_at_[hidden]> wrote:
>>
>> Ship it!
>>
>> Thank you for sticking with us through all these iterations!
>>
>> Tom.
>>
>> On 5/11/22 9:44 PM, Barry Revzin wrote:
>>> Done!
>>>
>>> Barry "Ship it?" Revzin
>>>
>>> On Wed, May 11, 2022 at 3:36 PM Tom Honermann
>>> <tom_at_[hidden]> wrote:
>>>
>>> Hi, Barry. We discussed in today's SG16 meeting and
>>> identified one last minor change to make. We then
>>> polled forwarding the paper to LWG with unanimous
>>> consent so this is definitely the last change!
>>>
>>> In 2.3.1, substitute "character" for "UCS scalar
>>> value" in the first sentence and in the table header.
>>>
>>> If /C/ is one of the UCS scalar
>>> values_characters_ in the table below, then the
>>> two characters shown as the corresponding escape
>>> sequence are appended to /E/:
>>>
>>> UCS scalar value_character_
>>> escape sequence
>>> U+0009 CHARACTER TABULATION |\t|
>>> U+000A LINE FEED |\n|
>>> U+000D CARRIAGE RETURN |\r|
>>> U+0022 QUOTATION MARK |\"|
>>> U+005C REVERSE SOLIDUS |\\|
>>>
>>> Tom.
>>>
>>> On 5/11/22 12:56 PM, Tom Honermann via SG16 wrote:
>>>>
>>>> I have a weak preference for "character" given that
>>>> the wording is intended to address Unicode and
>>>> non-Unicode behavior. I don't think we have any
>>>> normative uses of "code point" at present.
>>>>
>>>> The definition of "code point" we have via our
>>>> normative reference to ISO/IEC 10646 is: "value in
>>>> the UCS codespace". That doesn't really work for
>>>> the non-Unicode case and, regardless, would include
>>>> surrogate code points which I don't think we want
>>>> in this context.
>>>>
>>>> Tom.
>>>>
>>>> On 5/11/22 12:24 PM, Victor Zverovich via SG16 wrote:
>>>>> Thanks Tom and others for revising the wording.
>>>>> The latest version of the escaping section looks
>>>>> good to me with only one minor question: is it
>>>>> clear that "character" in
>>>>> https://brevzin.github.io/cpp_proposals/2286_fmt_ranges/p2286r8.html#pnum_14
>>>>> means a code point or shall we use the term code
>>>>> point instead?
>>>>>
>>>>> Cheers,
>>>>> Victor
>>>>>
>>>>> On Tue, May 10, 2022 at 6:32 PM Barry Revzin
>>>>> <barry.revzin_at_[hidden]> wrote:
>>>>>
>>>>>
>>>>>
>>>>> On Tue, May 10, 2022 at 1:31 PM Tom Honermann
>>>>> <tom_at_[hidden]> wrote:
>>>>>
>>>>> On 5/9/22 7:34 PM, Barry Revzin wrote:
>>>>>>
>>>>>>
>>>>>> On Mon, May 9, 2022 at 4:14 PM Tom
>>>>>> Honermann <tom_at_[hidden]> wrote:
>>>>>>
>>>>>> On 5/8/22 4:04 PM, Barry Revzin via
>>>>>> SG16 wrote:
>>>>>>>
>>>>>>>
>>>>>>> On Sun, May 8, 2022 at 9:22 AM
>>>>>>> Victor Zverovich
>>>>>>> <victor.zverovich_at_[hidden]> wrote:
>>>>>>>
>>>>>>> > One thing I noticed is that
>>>>>>> the wording about
>>>>>>> Grapheme_Extend is gone. I
>>>>>>> didn't know what this meant
>>>>>>> before, so I don't know now if
>>>>>>> this is a good removal or a bad
>>>>>>> removal.
>>>>>>>
>>>>>>> I don't recall any requests
>>>>>>> for removing it and think that
>>>>>>> it should be reintroduced.
>>>>>>>
>>>>>>> - Victor
>>>>>>>
>>>>>>> On Wed, May 4, 2022 at 10:44 PM
>>>>>>> Jens Maurer
>>>>>>> <Jens.Maurer_at_[hidden]> wrote:
>>>>>>>
>>>>>>> On 05/05/2022 04.08, Barry
>>>>>>> Revzin wrote:
>>>>>>> > I think I have applied
>>>>>>> this. Here's the rendered
>>>>>>> version:
>>>>>>> https://brevzin.github.io/cpp_proposals/2286_fmt_ranges/p2286r8.html#pnum_12
>>>>>>> <https://brevzin.github.io/cpp_proposals/2286_fmt_ranges/p2286r8.html#pnum_12>
>>>>>>>
>>>>>>> > How does this look?
>>>>>>>
>>>>>>> p2.2
>>>>>>>
>>>>>>> For each code sequence X in
>>>>>>> S that either encodes a
>>>>>>> single character or encoding
>>>>>>> state transition or that is
>>>>>>> a sequence of ill-formed
>>>>>>> code units is processed in
>>>>>>> order as follows:
>>>>>>>
>>>>>>> That feels like bad English
>>>>>>> grammar to me.
>>>>>>>
>>>>>>> Why "encoding", yet there is
>>>>>>> an "encodes" before that?
>>>>>>> Why "either" and there are
>>>>>>> three things that don't
>>>>>>> exactly correspond
>>>>>>> grammatically?
>>>>>>>
>>>>>>> Maybe make a bulleted
>>>>>>> sub-list with the three items
>>>>>>> so that the structure is clear.
>>>>>>>
>>>>>>> "If C is one of the UCS
>>>>>>> scalar values the table below,"
>>>>>>>
>>>>>>> add "in"
>>>>>>>
>>>>>>> better clarify: "the two
>>>>>>> characters shown as the
>>>>>>> corresponding escape
>>>>>>> sequence are appended to E"
>>>>>>>
>>>>>>>
>>>>>>> after p2.3.4, p2.5
>>>>>>>
>>>>>>> "simple-hexadecimal-digit-sequence"
>>>>>>>
>>>>>>> I would not re-use lexing
>>>>>>> grammar for a local placeholder,
>>>>>>> just say
>>>>>>> \u{/hex-digit-sequence/} or so.
>>>>>>>
>>>>>>>
>>>>>>> p2.5
>>>>>>>
>>>>>>> "Otherwise, X is a sequence
>>>>>>> of ill-formed code units. Each"
>>>>>>>
>>>>>>> -> "Otherwise (X is a
>>>>>>> sequence of ill-formed code
>>>>>>> units), each code unit ..."
>>>>>>>
>>>>>>>
>>>>>>> "U+0027 APOSTROPHE is
>>>>>>> escaped as \' while U+0022
>>>>>>> QUOTATION MARK is left
>>>>>>> unchanged."
>>>>>>>
>>>>>>> Can we rephrase that to
>>>>>>> avoid "is escaped as"? We
>>>>>>> were on such a good
>>>>>>> track to just append
>>>>>>> characters and avoid any
>>>>>>> judgment calls.
>>>>>>>
>>>>>>> suggestion "
>>>>>>> - for each character U+0027
>>>>>>> APOSTROPHE in S, the two
>>>>>>> characters \' are appended to E
>>>>>>> - U+0022 QUOTATION MARK is
>>>>>>> left unchanged"
>>>>>>>
>>>>>>>
>>>>>>> Jens
>>>>>>>
>>>>>>>
>>>>>>> Thanks Jens and Victor! I did my
>>>>>>> best to apply the suggested changes:
>>>>>>>
>>>>>>> * Updated rendered wording:
>>>>>>> https://brevzin.github.io/cpp_proposals/2286_fmt_ranges/p2286r8.html#pnum_12
>>>>>>> * New diff:
>>>>>>> https://github.com/brevzin/cpp_proposals/commit/3d93043f5c296810d7e18b11d5b7083143554309
>>>>>>>
>>>>>>>
>>>>>>> Hopefully, this gradient is slowly
>>>>>>> descending to the correct solution :-)
>>>>>>
>>>>>> Thanks, Barry. This appears to have
>>>>>> incorporated the parts of my prior
>>>>>> suggestions that did not have
>>>>>> opposition, so just minor issues
>>>>>> noted below.
>>>>>>
>>>>>> Discussion at the last meeting
>>>>>> <https://github.com/sg16-unicode/sg16-meetings#april-27th-2022>
>>>>>> revealed that we're failing to
>>>>>> specify the encoding used to
>>>>>> interpret /S/. Change p2 as follows:
>>>>>> (perhaps substitute "as described
>>>>>> below" for "as follows")
>>>>>>
>>>>>> The escaped string /E/
>>>>>> representation of a string /S/ is
>>>>>> constructed by encoding a
>>>>>> sequence of characters_as
>>>>>> follows._in t_T_he associated
>>>>>> character encoding /CE/ for charT
>>>>>> ([lex.string.literal]
>>>>>> <http://eel.is/c++draft/tab:lex.string.literal>)as
>>>>>> follows:_is used both to
>>>>>> interpret /S/ and to construct /E/._
>>>>>>
>>>>>> In p2.2, "code sequence" -> "code
>>>>>> unit sequence".
>>>>>>
>>>>>> In p2.3.4 and p2.5, I don't think we
>>>>>> should re-use the /hexadecimal-digit/
>>>>>> grammar term here. Just say,
>>>>>> "hexadecimal digits".
>>>>>>
>>>>>> Add the following note to p2.4 to
>>>>>> address a request by Hubert:
>>>>>>
>>>>>> Otherwise, if /X/ encodes a state
>>>>>> transition, the effect on /E/ is
>>>>>> unspecified._[ /Note:/ the intent
>>>>>> is that a state transition be
>>>>>> represented in /E/ such that its
>>>>>> original code unit sequence can
>>>>>> be reconstructed /- end note/ ]_
>>>>>>
>>>>>> Hubert pointed out during the last
>>>>>> meeting that we should not be trying
>>>>>> to interpret state transitions for
>>>>>> stateful encodings as I had
>>>>>> previously been trying to do. I think
>>>>>> we can now simplify p2.5:
>>>>>>
>>>>>> Otherwise (/X/ is a sequence of
>>>>>> ill-formed code units), each code
>>>>>> unit /U/ is appended to /E/ in
>>>>>> order as the sequence
>>>>>> /\x{hex-digit-sequence}/, where
>>>>>> /hex-digit-sequence/ is the
>>>>>> shortest hexadecimal
>>>>>> representation of /U/ using
>>>>>> lower-case hexadecimal
>>>>>> digits.When encoding a stateful
>>>>>> character encoding, these
>>>>>> additions should have no effect
>>>>>> on encoding state.
>>>>>>
>>>>>> In p3, we now need to drop "in a
>>>>>> Unicode encoding". I think the result
>>>>>> should also produce a string, not a
>>>>>> character.
>>>>>>
>>>>>> The escaped character_string_
>>>>>> representation of a character /C/
>>>>>> in a Unicode encoding is
>>>>>> equivalent to the escaped string
>>>>>> representation of a string of
>>>>>> /C/, except that:
>>>>>>
>>>>>> p4 should be removed now.
>>>>>>
>>>>>> The escaped character and escaped
>>>>>> string representations of a
>>>>>> character or string in a
>>>>>> non-Unicode encoding is unspecified.
>>>>>>
>>>>>> Hubert, the wording does not
>>>>>> explicitly address your request to be
>>>>>> able to specify spacing and separator
>>>>>> characters as a set of encoding
>>>>>> agnostic code point values. I think
>>>>>> the existing wording suffices to meet
>>>>>> your goals since an implementation
>>>>>> can document a method of identifying
>>>>>> the set of escaped characters by, for
>>>>>> example, specifying characters in
>>>>>> EBCDIC 1047 and describing how to map
>>>>>> those to other code pages. If you
>>>>>> don't agree, could you suggest how
>>>>>> the wording might be updated to
>>>>>> better address your concern?
>>>>>>
>>>>>> Tom.
>>>>>>
>>>>>>
>>>>>> Thanks, Tom! I applied these changes. The
>>>>>> diff can be found here:
>>>>>> https://github.com/brevzin/cpp_proposals/commit/6745d72f8c002b7ce8811f0c6aeb5591cff97d54
>>>>>
>>>>> Thanks, Barry. This looks good to me
>>>>> modulo Hubert's additional tweak.
>>>>>
>>>>> One last thing I noticed. The example
>>>>> section has this:
>>>>>
>>>>> string s4 = format("[{:?}]",
>>>>> string("\0 \n \t \x02 \x1b", 9));
>>>>>
>>>>> // s4 has value [\u{0} \n \t \u{2} \u{1b}]
>>>>>
>>>>> That example depends on the encoding being
>>>>> ASCII-based in order for the \x02 and \x1b
>>>>> escapes to be interpreted as characters
>>>>> \u{2} and \u{1b}. Similarly, s5 and s6
>>>>> have UTF-8 dependencies. Perhaps we should
>>>>> add a comment?
>>>>>
>>>>> string s0 = format("[{}]",
>>>>> "h\tllo"); // s0 has
>>>>> value: [h llo]
>>>>> string s1 = format("[{:?}]",
>>>>> "h\tllo"); // s1 has
>>>>> value: ["h\tllo"]
>>>>> string s2 = format("[{:?}]", "Спасибо,
>>>>> Виктор ♥!"); // s2 has value:
>>>>> ["Спасибо, Виктор ♥!"]
>>>>> string s3 = format("[{:?}] [{:?}]",
>>>>> '\'', '"'); // s3 has value: ['\'', '"']
>>>>> _// The following examples assume use
>>>>> of the UTF-8 encoding._
>>>>> string s4 = format("[{:?}]",
>>>>> string("\0 \n \t \x02 \x1b", 9));
>>>>>
>>>>> // s4 has value [\u{0} \n \t \u{2} \u{1b}]
>>>>> string s5 = format("[{:?}]",
>>>>> "\xc3\x28"); // invalid UTF-8
>>>>>
>>>>> // s5 has value: ["\x{c3}\x{28}"]
>>>>> string s6 = format("[{:?}]",
>>>>> "🤷🏻‍♂️"); // s6
>>>>> has value: ["🤷🏻\u{200d}♂\u{fe0f}"]
>>>>>
>>>>> I never got around to translating
>>>>> "Спасибо, Виктор ♥!" until now. Very nice :)
>>>>>
>>>>> Tom
>>>>>
>>>>>
>>>>> Applied Hubert's change and added this
>>>>> comment:
>>>>> https://brevzin.github.io/cpp_proposals/2286_fmt_ranges/p2286r8.html#pnum_12
>>>>> Thanks!
>>>>>
>>>>> The decreasing rate of requested changes is
>>>>> encouraging!
>>>>>
>>>>> Barry
>>>>>
>>>>>
>>>>
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