array[-1] -- permitted?
George Kyriazis
kyriazis at rpics
Thu Sep 22 16:42:13 AEST 1988
In article <2583 at ingr.UUCP> jones at ingr.UUCP (Mark Jones) writes:
>In article <1988Sep19.164701.11136 at ateng.uucp>, chip at ateng.uucp (Chip Salzenberg) writes:
>> According to news at ism780c.isc.com:
>> >But consider what might have happened had dpANS mandated that the compution
>> >of a pointer to x[-1] be a valid operation.
>>
>> Okay, let's imagine: X3J11 says that x[-1] must be valid.
>> then: int must be 32 bits.
>
>Excuse my ignorance, but why must an int be 32 bits for the above to work?
>
>> then: address space must be linear.
>
>Does X3J11 say that the contents of x[-1] must be valid?
>
>Mark Jones
Excuse for the question, but that is the first time I am looking at that
subject and I don't see any reason why x[-a] can't be permitted, mainly
for two basic reasons:
(a) x[a] == *(x+a) therefore x[-1] == *(x-1), which looks
perfectly ok to me.
(b) yacc uses array[-1]. If it is considered invalid, that will mean
that yacc has to be rewriten for the new standard?
Am I missing something?
George Kyriazis
kyriazis at turing.cs.rpi.edu
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