From: wconrad@...
Date: 2002-05-31T02:56:52+09:00
Subject: Re: Infinity (?!)

On Thu, May 30, 2002 at 11:04:30PM +0900, Sean Russell wrote:
> Dossy wrote:
> 
> > Float allowing division by zero is certainly not of least surprise
> > to me.  ;-)
> 
> Yeah, I think it is sort of silly, too.  From what I remember of my math, 
> dividing by zero is "illegal".

True, but the math we do with floats bears only a passing resemblance
to the math we learned in our youth (floats are not reals, no matter
what Wirth says).  Nor is it too odd to define 1 / 0 as infinity --
infinity is a just as reasonable a result as "you can't do that,"
considering that 1 / n approaches infinity as n approaches 0.

Computer math is a little surprising.

> However, IEEE 754 (Institute of Electrical and Electronics Engineers. IEEE 
> Standard for Binary Floating-Point Arithmetic. ANSI/IEEE Std 754-1985.) 
> defines rules for operations such as this, and it specifies that n/0 -> 
> Infinity, -n/0 -> -Infinity, and 0/0 -> NaN.  Because of this, I'm a little 
> surprised that Integer math in Ruby doesn't follow the same rules.

I'd be very surprised to find IEEE 754 applied to integers.  Integers
are quite different animals.

        Wayne Conrad