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From: torek@elf.ee.lbl.gov (Chris Torek)
Newsgroups: comp.lang.c
Subject: Re: When do you use "if ( a = b )"? (was Re: Funny mistake)
Message-ID: <11309@dog.ee.lbl.gov>
Date: 22 Mar 91 07:25:12 GMT
References: <8148@rsiatl.Dixie.Com> <15481@smoke.brl.mil> <775@camco.Celestial.COM> <65837@eerie.acsu.Buffalo.EDU> <1991Mar18.195351.11985@unlv.edu> <11109@dog.ee.lbl.gov> <dxj+VD@ppcger.ppc.sub.org>
Reply-To: torek@elf.ee.lbl.gov (Chris Torek)
Organization: Lawrence Berkeley Laboratory, Berkeley
Lines: 48
X-Local-Date: Thu, 21 Mar 91 23:25:12 PST

[I wrote: `if your compiler generates different code for embedded
assignments than for separate assignments, that compiler is not worth
what you paid for it.']

In article <dxj+VD@ppcger.ppc.sub.org> Sepp@ppcger.ppc.sub.org (Josef Wolf)
writes:
>You might be right in this point of view, but...
[and goes on to argue that embedded assignment tends to be clearer.]

I happen to agree---most often, a loop like:

	while ((c = getchar()) != EOF) {
		do some work;
	}

is MUCH better, stylistically, than

	c = getchar();
	while (c != EOF) {
		do some work;
		c = getchar();
	}

(Never mind translating into `for' loop syntax :-) )

>Well, the above is _my_ opinion. You have to find _your_ way to get
>around this problem.

Do not make the mistake of thinking that every argument I make is a
direct clue to my own opinions.  I could, for instance, show how VMS
is better than <pick some version here> Unix at some particular task.
(Such tasks do exist, especially with older Unixes.)  Nonetheless, I
have managed to avoid VMS systems for many years now, and plan to
continue avoiding them.

In this particular case, I would be quite happy with a compiler that
warns about

	if (a = expr) ...

but not about

	if ((a = expr) != 0) ...

and I tend to write the latter when I mean `assign, then test the result'.
-- 
In-Real-Life: Chris Torek, Lawrence Berkeley Lab CSE/EE (+1 415 486 5427)
Berkeley, CA		Domain:	torek@ee.lbl.gov