Re: [RFC/PATCH]: transform builtin isdigit (okay with locales?)

[Dale Johannesen <dalej at apple dot com>]

On Apr 8, 2004, at 2:07 PM, Paul Koning wrote:

> > > > > > "Kaveh" == Kaveh R Ghazi <ghazi@caip.rutgers.edu> writes:
>
>  Kaveh> I've seen in various source code people define isdigit(c) to
>  Kaveh> (unsigned)(c) - '0' <= 9
>
>  Kaveh> I believe that even in the various dialects of EBCDIC, the
>  Kaveh> digits '0' to '9' are continuous and ascending.  (And I don't
>  Kaveh> think we have any more EBCDIC targets anyway.)  So I thought
>  Kaveh> perhaps it's okay to do this transformation inside GCC.
>
>  Kaveh> Just to confirm though, this doesn't hold up in the face of
>  Kaveh> locales, right?  So maybe not...
>
> If "isdigit" is defined to match a digit in the charset of the current
> locale, then no -- what you describe wouldn't match Arabic digits, nor
> Chinese/Japanese ones, never mind lesser known locales.

But it isn't.  "isdigit" is defined to match a decimal digit "as 
defined in 5.2.1" (c99)
which requires the 10 familiar digits, and further requires they have 
values
in consecutive ascending order.  Locales don't affect this that I can 
see.