Weird numerical behavior regarding zero

From: matthias_k (nospam_at_digitalraid.com)
Date: 01/25/05 

Date: Tue, 25 Jan 2005 17:23:19 +0100

Hi,

I am currently implementing a solver for linear optimization problems
using the revised simplex method and I stumbled accross some strange
behavior regarding the treatment of the number 0.
I am not sure whether this is compiler or language related though.

The first problem is, that there are two representations of zero, namely
+0 and -0. Does IEEE for floating points allow this? Maybe I didn't
activate IEEE floating point numbers?
Anyway, this does have some very annoying consequences, since this
expression:
    x / -0 yields -inf (x is positive).

Which brings me to my second question. Shouldn't division by zero make
my computer go up in flames or so? Because, on my system (Arch Linux 0.7
i686) with my compiler (g++ 3.4.3), dividing by zero is allowed.
In fact, it yields +inf when dividing by +0 and -inf when dividing by
-0, given that the nominator (is that the english term for "Zähler"?) is
positive of course.

Any comments/ideas?

Regards,
Matthias

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