On Fri, 30 November 2001, "Barubary" wrote:

> If there is a positive infinity and a negative infinity, isn't there a

> positive zero and a negative zero, the reciprocals of the infinities?

Given the two assumtions:

If there is a positive and negative infinity which are distinct

_AND_

Both the positive and negative infinities are in the set with which you are permitted to perform divisions

_then maybe_ you can come up with a model that includes both a positive and a negative zero that's useful. However, the set you end up with will be sadly lacking in many of the sensible properties that we are familiar with with the reals.

So _don't_ make those two assumtions unless you're prepared for the consequences.

IEEE754 and 854 are both working models for arithmetic which contains the concept of +/-0 and +/-inf. However, they are _lousy_ as a substitute for the real reals.

Phil

Don't be fooled, CRC Press are _not_ the good guys.

They've taken Wolfram's money - _don't_ give them yours.

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