I think there's another useful guarantee that could be provided, but I'm
not sure whether it should be done as part of this proposal: In any
encoding, it looks like alphabetic characters always appear in their
lexicographical order, even if they aren't always contiguous.

Consequently, (a <=> b) is meaningful and useful between two characters if
you know that a and b are letters.

On Sat, 28 Feb 2026 at 10:04, Jan Schultke <janschultke_at_[hidden]>
wrote:

> Hi,
>
> https://isocpp.org/files/papers/D4039R0.html
>
> In the recent discussion of D4040R0, it was brought up that C2y now
> provides the guarantee that hexadecimal digit characters are contiguous.
> This was done by
> https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3192%2epdf
>
> I've drafted up a proposal that adopts that guarantee into C++. Feedback
> is welcome.
>
> I expect we can make this a DR against C++98 and pretend it's always been
> guaranteed.
>
>
>
> Jan
>