Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ukma!rutgers!bellcore!texbell!sugar!ficc!peter
From: peter@ficc.uu.net (Peter da Silva)
Newsgroups: comp.lang.c
Subject: Re: comma operator:  keep away?
Message-ID: <3953@ficc.uu.net>
Date: 24 Apr 89 13:53:51 GMT
References: <19913@iuvax.cs.indiana.edu> <10092@smoke.BRL.MIL> <1104@aplcen.apl.jhu.edu>
Distribution: usa
Organization: Xenix Support
Lines: 32

In article <1104@aplcen.apl.jhu.edu>, bink@aplcen.apl.jhu.edu (Ubben Greg) writes:
> In article <2179@pur-phy> (Sho Kuwamoto) writes:
> >	for(i=0, p=head; p->next != NULL; i++, p=p->next)

> People too often cram expressions in the for(;;) that are not related
> to the loop control, just to avoid a couple of extra lines.

I dispute that's the motivation in this case. But putting the i=0 and i++
in the loop you're providing extra information: that the variable 'i' is
tightly bound to the loop, and may be serving as a manufactured loop index.
The alternative:

	i = 0;
	for(p=head; p->next != NULL; p=p->next)
	{
		...
		i++;
	}

implies that 'i' might not be bound to the loop, and also means that you
would have to special-case any 'continue' statement in the expression if it
is so bound.

		if(gottagetouttahere)
			i++, continue;	/* :-> */

(Yes, I know you can't do that).
-- 
Peter da Silva, Xenix Support, Ferranti International Controls Corporation.

Business: uunet.uu.net!ficc!peter, peter@ficc.uu.net, +1 713 274 5180.
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