[Python-Dev] Caching float(0.0)
"Martin v. Löwis"
martin at v.loewis.de
Tue Oct 3 19:27:05 CEST 2006
Nicko van Someren schrieb:
> It's only a semantic change on platforms that "happen to" use IEEE
> 754 float representations, or some other representation that exposes
> the sign of zero.
Right. Later, you admit that this is vast majority of modern machines.
> It would be instructive to understand how much, if any, python code
> would break if we lost -0.0. I'm do not believe that there is any
> reliable way for python code to tell the difference between all of
> the different types of IEEE 754 zeros and in the special case of -0.0
> the best test I can come up with is repr(n)=='-'. Is there an
> compelling case, to do with compatibility or otherwise, for exposing
> the sign of a zero? It seems like a numerical anomaly to me.
I think it is reasonable to admit that
a) this change is a change in semantics for the majority of the
b) it is likely that this change won't affect a significant number
of applications (I'm pretty sure someone will notice, though;
someone always notices).
More information about the Python-Dev