Re: About -0 and type complex

[Daniel J Sebald]

On 10/09/2012 10:03 PM, Michael D. Godfrey wrote:
> On 10/09/2012 08:55 PM, Daniel J Sebald wrote:
[snip]
> ========================
> But, of course, nothing can be done with x as complex
> that does not explicitly modify its imaginary part.

I know.

It would be really nice to have useful limit/supremum representation, 
and it probably can be done but at a cost of extra CPU for something 
that may not find a great deal of use.  Perhaps a mode that has more 
robust limit checking or something.  The +0, -0 really only makes sense 
for limits, otherwise it is just zero.  For example, this sort of thing

octave-cli:14> x = -0
x = -0
octave-cli:15> x
x = -0

in most cases should just produce zero.  The problem is that if some 
routine wants to set the value of a variable to -0 meaning the limit or 
supremum, it is the same expression as "- 0".  Maybe if it were +Z, 0, 
and -Z.  Or actually, the following syntax might work (this isn't actual 
output, I'm just hypothesizing)

oct> x = -0
x = 0
oct> x = (-0)
x = -0
oct> x = (+0)
x = +0

but there is no IEEE 754 representation for +0.  Because of that, one 
can't devise any system that uses the underlying math libraries without 
imposing some first pass on the data that causes a performance hit.

Dan