bug#51011: [GNU sort] Numerical sort with delimiter may be broken (bug)

[Pádraig Brady]

On 08/10/2021 21:48, Paul Eggert wrote:
> On 10/8/21 6:37 AM, Pádraig Brady wrote:
> > The difference here is due to ',' being treated as a thousands sep,
> > not a decimal point.
>
> Oh, thanks. Of course! I should have figured that out myself.
>
> It is unfortunate that "," is treated as a thousands seperator even
> though it's obviously not one (as it's not followed by 3 decimal
> digits). I don't think POSIX requires this behavior; it's not clear to
> me that POSIX even allows it.

Well in general it's not a thousands separator, rather a grouping character,
and groups can be in 2, 3, 4, and even 5.  So I don't think we should
change the logic here.

> This bug report suggests that we should alter the code so that 'sort -n'
> acts more like common practice, and requires thousands separators to be
> in the right places in order to treat nearby digits to be part of the
> number. Alternatively, we could document the existing behavior (even if
> it's not clear that it conforms to POSIX).

What we can do is have --debug warn when there is an overlap
in --field-separator and the grouping and decimal characters
when using numeric keys.  I'll have a look at that tomorrow.

cheers,
Pádraig