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From: Eric Sosman <esos...@ieee-dot-org.invalid>
Newsgroups: comp.lang.c,comp.std.c
Subject: Re: About the array subsripting operator
Followup-To: comp.std.c
Date: Thu, 30 Aug 2012 12:58:26 -0400
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On 8/30/2012 12:32 PM, Kirilenko wrote:
> Hey c.l.c. !
>
> I was reading the C11 standard (�6.5.2.1) :
>
>> The definition of the subscript operator [] is that E1[E2] is identical to
>> (*((E1)+(E2))).
>
> I would like to know why are brackets around E1 necessary (they were missing
> in the C89 standard), ie in which case can (*(E1+(E2))) be different from
> (*((E1)+(E2))) ?

     The parentheses would only make a difference if E1 were an
expression involving operators of lower precedence than `+'.
But any such operator would also have lower prececence than `[]',
so E1 would already need to be parenthesized:

	(which ? array1 : array2) [i]
not
	which ? array1 : array2 [i]

Perhaps the extra parentheses were added for clarity's sake, in
the fear that someone might think E1 in the first line above
was the "bare" `which ? array1 : array2', which would make hash
of the stated equivalence.

     (Questions about "Why is the Standard written in thus-and-such
a way?" will probably do better in comp.std.c than in comp.lang.c.
CC'ed, and follow-ups set.)

-- 
Eric Sosman
esos...@ieee-dot-org.invalid