On 09/14/2016 05:09 PM, Bill Woodger wrote:
> Yes, "the rules of algebra" has lead to a minus zero... but it is still zero,
> the sign for zero has no significance in algebra.
>
> In two's-complement, there is no negative zero.
>
> In packed-decimal 'rithmetic, there is, as explained in the PoP. The sign of
> the result is according to the rules of algebra, even when the result is zero.
>
>
I'm not sure what you mean by "the rules of algebra" lead to minus
zero. In algebra and mathematics "0" is "0", neither positive or
negative. A signed zero is not a concept in algebra but purely an
artifact of the way we choose to represent the abstract concept of real
and natural numbers on a physical device -- namely, the choice of a
sign-magnitude representation, with one bit reserved for sign. The sign
bit is meaningless mathematically for a zero magnitude value but must
still have some state in the physical representation for the number..
Some architectures may choose to allow such "-0" values to have special
meaning rather than ever allowing it to be used as a zero value in a
computation or be generated for a zero result.
Joel C. Ewing
--
Joel C. Ewing, Bentonville, AR jcew...@acm.org
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