Re: [pure-lang-users] complex 0

[Albert G. <Dr....@t-...>]

Eddie Rucker wrote:
>  > (2.0+:1.0)/0.0;
>  inf+:inf
>  > (2.0+:1.0)/(0.0+:0.0);
>  nan+:nan
> 
> Um. Should this be consistent?

Maybe, not sure. AFAICS, there are three possible perspectives:

- (2.0+:1.0)/0.0 has an exact 0 in the imaginary part of the divisior, 
so it's actually a vector multiplied with an infinite scalar, whereas in 
the case of (2.0+:1.0)/(0.0+:0.0) it's an inexact zero so the general 
formula must be used which yields nan+:nan because a zero meets a pole 
in both components. (OTOH, if we take this view then probably 
(2.0+:1.0)/(0.0+:0) should yield the same result as the former, whereas 
right now it yields the same result as the latter.)

- The divisor should be promoted to a complex 0.0+:0.0 in the first 
case, so you get nan+:nan in either case.

- The divisior should be promoted to a real 0.0 in the second case, 
yielding inf+:inf in either case. That's what I get with mzscheme, but 
it doesn't make any real sense (pun intended) to me because 0.0+:0.0 is 
*not* the same as 0.0+:0 (or just 0.0) in the IEEE 754 sense (the 
imaginary zero might as well be just an underflow).

I haven't checked the Goldberg paper, though. Maybe there's a "more 
defined" formula in the complex divisor case?

Albert

-- 
Dr. Albert Gr"af
Dept. of Music-Informatics, University of Mainz, Germany
Email:  Dr....@t-..., ag...@mu...
WWW:    http://www.musikinformatik.uni-mainz.de/ag