On Mon, Sep 28, 2026, 05:14 Yongwei Wu via SG16 <sg16_at_[hidden]>
wrote:

> First, I think the paper is a fantastic summary.
>
> Second, the encoding list in the Google Sheet may contain some false
> positives. As a Chinese, I noticed the weird GBGBK immediately. I have no
> idea what it is, and googling does not reveal interesting results, and
> GBGBK does not exist on macOS (Sequoia) or Ubuntu (24.04 LTS). Claude
> Sonnet says it might be an internal conversion module, but it does not give
> much detail. Currently I do not think it is worthwhile to dig out what it
> really is.
>
> I think there are fewer in-use encodings that require digraphs than the
> spreadsheet implies. From what I can recognize, GBBIG5 may be similar to
> GBGBK. What is ISO646 (as versus ISO646-something), which does not really
> make sense? On macOS there is an ISO646-BASIC:1983 (I don't see
> an equivalent on Ubuntu), but it behaves differently than the spreadsheet
> too.
>

That table is missing some critical information: how many if these
encodings are in common use, and used to write C++ code (or code in general)

Or rather, the question of whether a given encoding needs digraphs is sort
of irrelevant, the question is whether digraphs are used.

EBCDIC-derived encodings use trigraphs and we should keep accepting the
magical phase one mapping of trigraphs to be a conforming extension.
And if we really want to do encoding agnostic pragma without trigraphs
(which there is no evidence of anyone doing today), we don't need digraphs.

As Matthias's research shows, digraphs were a solution to a problem that no
longer existed by the time digraphs where shoved in the standard, and
because of internalization, internet, standardization of keyboards, OSes,
programming languages, communication protocols and so forth, products that
don't support the range of ASCII characters would not have been viable,
since before the 00s.

Shift JIS is the only popular encoding that is not ASCII compatible but we
are all happy to pretend that ¥ and \ are the same character (same for
~/overline). Which is bonkers, but it is what it is. (Tom table also makes
that mistake).



> My 2 cents.
>
> On Sun, 27 Sept 2026 at 11:21, Tom Honermann via SG16 <
> sg16_at_[hidden]> wrote:
>
>> On 9/24/26 8:27 PM, Matthias Wippich wrote:
>> > On Thu, Sep 24, 2026 at 10:20 PM Tom Honermann via SG16
>> > <sg16_at_[hidden]> wrote:
>> >> If possible, it would be helpful to include that content as an
>> appendix in the paper itself.
>> > I'll try to do that, but I'm worried that it'll be impossible to
>> > format correctly. Maybe a link to a CSV export of that table (hosted
>> > on github/gist) is sufficient? The google link might indeed not be
>> > very stable.
>>
>> Any original content used to justify the motivation or design choices
>> really should be in the paper for the historical record.
>>
>> Attached is a quick hack job I did that I would personally call good
>> enough if you want to use it. The HTML isn't pretty and I didn't try to
>> style it in any way, so there is plenty of opportunity to make it
>> prettier.
>>
>> Tom.
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>
>
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> Yongwei Wu
> URL: http://wyw.dcweb.cn/
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