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From: Florian Weimer <fw@deneb.enyo.de>
Newsgroups: comp.lang.ada,comp.lang.c,comp.lang.c++
Subject: Re: Subtle Bugs, kudos Ada (was How Ada ...Red Code ...)
Date: Wed, 29 Aug 2001 04:17:22 +0200
Organization: Enyo's not your organization
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Date: 2001-08-29T04:17:22+02:00
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Joe Maun <reply_to@yahoo.com> writes:

>> Under ones' complement, the bit pattern 1111...111 is non-negative;
>
> Wrong. If it's not a trap representation it's *negative* zero (ISO/IEC
> 9899:1999 - 6.2.6.2[2]).
>
>> it represents the value zero. When this is right shifted by 1, it must
>> result in the value 0.
>
> Since it is a negative value, the resulting value is
> implementation-defined. The resulting bits must have the form ?111...11.

How do you derive that from the standard?  From the phrase 'The result
of E1 >> E2 is E1 right-shifted E2 bit positions.'?  What happens when
we write down the bits starting with the least significant bit?