[PATCH][RFC] Avoid table lookup in isascii, isxdigit.

[Paul Eggert]

On 04/12/13 13:42, Rich Felker wrote:
> #define isdigit(c) ((unsigned)(c)-'0'<10)

Unfortunately, this implementation mishandles some
obscure usages, e.g.,:

   double eof = EOF;
   return isdigit (eof);

on systems where the implementation raises a signal
when converting an out-of-range floating-point value
to unsigned.