Path: utzoo!mnetor!uunet!husc6!mailrus!nrl-cmf!cmcl2!brl-adm!brl-smoke!gwyn
From: gwyn@brl-smoke.ARPA (Doug Gwyn )
Newsgroups: comp.lang.c
Subject: Re: Character handling functions -- Jan 88, dpANS
Message-ID: <7571@brl-smoke.ARPA>
Date: 28 Mar 88 13:37:22 GMT
References: <6192@dhw68k.cts.com>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 15
Keywords: isalpha islower isupper locale confusion

In article <6192@dhw68k.cts.com> david@dhw68k.cts.com (David H. Wolfskill) writes:
>1)	It would seem to be possible for a character -- interpreted in a
>	locale other than the "C" locale -- to cause isalpha to return
>	true, yet cause both isupper and islower to fail to return true.

Yes, this is right.  Not all character sets have a meaningful concept
of "case".  (Consider Chinese.)  Instead of arbitrarily picking either
lower or upper (or both), the implementor can simply tell the truth.

>2)	Similarly, it would seem to be possible for a character to be
>	able to cause isalpha to fail to return true, and yet cause
>	either (or both!) of isupper and islower to return true.

No, read the specification of isalpha again.  islower => isalpha
and  isupper => isalpha  but not the converse.