Path: utzoo!attcan!uunet!wuarchive!usc!elroy.jpl.nasa.gov!zardoz.cpd.com!dhw68k!felix!asylvain
From: asylvain@felix.UUCP (Alvin "the Chipmunk" Sylvain)
Newsgroups: comp.lang.c
Subject: Re: Is there a good example of how toupper() works?
Keywords: converting upper/lower case macros
Message-ID: <152638@felix.UUCP>
Date: 25 Oct 90 21:42:09 GMT
References: <1990Oct17.170914.683@wpi.WPI.EDU> <11021@hubcap.clemson.edu> <152580@felix.UUCP>
Sender: daemon@felix.UUCP
Reply-To: asylvain@felix.UUCP (Alvin "the Chipmunk" Sylvain)
Organization: FileNet Corp., Costa Mesa, CA
Lines: 36

Ye gadz, recursive follow-ups!

In article <152580@felix.UUCP> asylvain@felix.UUCP,
  I wrote:
> In article <11021@hubcap.clemson.edu> svissag@hubcap.clemson.edu
> (Steve L Vissage II) writes:
> > From article <1990Oct17.170914.683@wpi.WPI.EDU>, by profesor@wpi.WPI.EDU
> > (Matthew E Cross):
> > > Nope, won't work - the return value of 'toupper' is undefined if the input
> > > is not a lowercase character.
> >   
> > So define your own toupper() macro.  That's what I did.
> > #define toupper(ch) ((ch<123 && ch>96) ? ch-32 : ch)
> 
> Two points: first, your macro is *disgustingly unreadable* (and probably
> incorrect ...haven't checked).  This is better:
> 
> #define toupper(ch) (((ch) >= 'a' && (ch) <= 'z') ? (ch) + 'A' - 'a' : (ch))
> #define tolower(ch) (((ch) >= 'A' && (ch) <= 'Z') ? (ch) + 'a' - 'A' : (ch))

Upon re-reading this, I've decided that it's not *much* better from a
readability point of view.  Try this:

#define toupper(ch) (((ch) >= 'a' && (ch) <= 'z')      \
                                ?  (ch) + 'A' - 'a'     \
				:  (ch))

#define tolower(ch) (((ch) >= 'A' && (ch) <= 'Z')      \
                                ?  (ch) + 'a' - 'A'     \
				:  (ch))

Please note that spaces are deliberate.  This is also what is known as a
"dangerous" macro, in that if you pass it something like '*ch++', your
results may not be what you expect.  Therefore, following convention,
it ought to be TOUPPER and TOLOWER as warning.  I still maintain that
you should forget the whole thing and use the library functions.