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devel / alt.lang.asm / Re: 0.0 / 0.0 = -NAN ?

Re: 0.0 / 0.0 = -NAN ?

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https://www.novabbs.com/devel/article-flat.php?id=263&group=alt.lang.asm#263

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From: kle...@unibwm.de (Herbert Kleebauer)
Newsgroups: alt.lang.asm
Subject: Re: 0.0 / 0.0 = -NAN ?
Date: Sat, 30 Apr 2022 21:02:10 +0200
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by: Herbert Kleebauer - Sat, 30 Apr 2022 19:02 UTC

On 30.04.2022 17:31, Skybuck Flying wrote:

> When exception masks are all enabled to stop the processor from > throwing floating point exceptions the following calculation
> produces a somewhat strange result:
>
> 0.0 / 0.0 = -nan

Why is this strange? 0/0 is undefined and therefore "Not A Number"

> Problem is with the code, example:
>
> T := 0;
> D := 0.0 / 0.0;
> P := T * D;
>

Why should P be zero? Suppose T=x and D=x/x^2
For x=0 you get T=0, D=0/0 and you say P should be 0,
but P=T*D = x*x/x^2 = 1

> This screws up P. instead of P being zero, P is now also -NAN ?!?

"Something" multiplied with "NotANumber" is also "NotANumber" even if the
"something" is zero.

Subject	Author
Re: 0.0 / 0.0 = -NAN ?	Herbert Kleebauer