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From: arnold@ucsfcgl.UUCP (Ken Arnold%CGL)
Newsgroups: net.lang.c
Subject: Re: CTRL(X) in ANSI standard (last one I hope)
Message-ID: <507@ucsfcgl.UUCP>
Date: Tue, 21-May-85 20:30:46 EDT
Article-I.D.: ucsfcgl.507
Posted: Tue May 21 20:30:46 1985
Date-Received: Fri, 24-May-85 03:55:04 EDT
References: <10747@brl-tgr.ARPA>
Reply-To: arnold@ucsfcgl.UUCP (PUT YOUR NAME HERE)
Organization: UCSF Computer Graphics Lab
Lines: 29

In article <10747@brl-tgr.ARPA> Purtill@MIT-MULTICS.ARPA (Mark Purtill) writes:
>I'm suprised no one caught me on this. When I said
>>#define CTRL(XX) ( ($XX)[0] & '\037')
>I should have said
>>#define CTRL(XX) ( (#XX)[0] & '\037')
>(ie, the $ should have been a #!!)  Sorry about that...

Unless the compiler is incredibly smart, this won't work in 'case'
statements, which is rather important.  Although "a"[0] is, in fact,
a constant, it is only a constant because it is a constant offset
into a *constant array*, which is a rather unusual beast.  The VAX
pcc doesn't figure this out.  Try this on your compiler and see if it
does:

		switch (i) {
		  case "a"[0]:
			break;
		}

Actually, when you think about it, since strings are writeable, "a"[0]
is NOT a constant, since someone else might modify the string.  It is
an indirection off of a constant location, but it is not a constant.

Face it.  We are going to have to kill ourselves trying to work around
the standard committee's refusal to let C work the way it has been working.
I have made my opinion on this known ad nauseum, I'm sure, so I'll just
leave it alone for now...

		Ken Arnold