> In the architectural view, isw?xdigit(c) is not always true when
> isw?digit(c) is true, because SUSv3 defines 'digit' class and
> 'xdigit' class individually.  ctype.h would rathar be changed than
> iswctype.c.  The current ctype.h (derived from 4.3BSD) is not
> sufficient to conform to SUS and we need to overhaul ctype.h.

charactors in digit class are automatically included in xdigit.
see "Valid Character Class Combinations" in susv3.

YAMAMOTO Takashi