complex arithmetic in gcc (and various standards)

[Paolo Carlini]

Hi Gaby

>| > My question was a slightly different one. To me it is not clear whether the 
>| > standard allows the treatment of (r,0) as r in complex operations. For 
>| > example: is it allowed to handle (r,0)*(x,y) as r*(x,y)?
>| 
>| I don't think so; at least, it might affect negative 0.
>
>Hmm, how?
>
I'm not sure if the following is exactly Joseph' point, but I'd like to 
know your opinion about it anyway: if you look to Comment #19 in the 
audit trail of PR 28408, I noticed that, due to the rule about signed 
zero (with default rounding):
   
    (+0) + (-0) = +0

the result of the "same" multiplication considered as complex * complex 
(vs complex * real) has a different sign for the zero imaginary component.

Paolo.