Date: Fri, 10 Aug 2001 15:46:30 -0700 From: "brian o'shea" <boshea@netapp.com> To: Raymond Wiker <Raymond.Wiker@fast.no> Cc: les@safety.net, Rob <europax@home.com>, "hackers@FreeBSD.ORG" <hackers@FreeBSD.ORG> Subject: Re: the =+ operator Message-ID: <20010810154630.A27553@netapp.com> In-Reply-To: <15220.9386.441669.962830@raw.grenland.fast.no>; from Raymond Wiker on Fri, Aug 10, 2001 at 08:15:06PM %2B0200 References: <3B73F0BC.548D40B3@home.com> <200108101446.HAA99867@safety.net> <15220.9386.441669.962830@raw.grenland.fast.no>
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On Fri, Aug 10, 2001 at 08:15:06PM +0200, Raymond Wiker wrote:
>
> This is actually wrong - the += and -= operators were
> originally written as =+ and =-. This is obviously ambiguous, given
> the fact that whitespace is ignored.
Why does this have to be ambiguous? Consider this:
int o = 2;
int *p = &o;
int q = 8;
int r;
r = q/*p /* comment */;
printf("r == %d\n", r);
Is this equivalent to the following:
r = q / *p;
Or is it equivalent to this:
r = q /* p /* comment */ ;
C disambiguates between these two possible interpretations by matching
the largest possible token. Thus, it is taken to be equivalent to:
r = q;
In other words, these two lines are not equivalent:
r = q/*p /* comment */;
r = q/ *p /* comment */;
So, the =+ operator could be interprited correctly as long as it is the
largest possible token. It does leave more of an opportunity for human
misinterpritation, while my example is less likely to be seen.
-brian
--
Brian O'Shea "Stare not too deeply into the pen, <boshea@netapp.com>
3.3.163(PEN) lest the pen stare back into you." (408) 822-3249
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