need clarification on -0

[Mark Dickinson]

On Nov 28, 8:39 pm, Tim Roberts <t... at probo.com> wrote:
> moijes12 <moije... at gmail.com> wrote:
>
> >I know the value -0 is quite meaningless and makes little sense.But I
> >was just fiddling.I am unable to figure out the below result
>
> >>>> -0 and True
> >0 ----------> (Why is this 0 and not say True or False)
> >>>> -0 and false
> >0
> >>>> -0 or True
> >True
>
> >Could someone please provide me some resources on how these operations
> >take place.I'd wanna find it out myself
>
> Actually, there ARE computers where you might not see this result.
> Virtually all of the processors on which Python runs use two's complement
> arithmetic.  In two's complement, there is no separate value called -0.  0
> and -0 have the same bit representation.
>
> In one's complement, -0 and 0 have different representations.

While that's true, I think the implementation of Python is
such that the Python objects -0 and 0 should always be
indistinguishable even on machines where the underlying
architecture represents integers using ones' complement or
sign-magnitude.

At least that's certainly the intention:  there are bits of
CPython's source code that are deliberately written in
convoluted ways in order to avoid the assumption of two's
complement.  But I have a nasty suspicion that, were Python
ever unlucky enough to meet a ones' complement machine,
we'd quickly find that there were many *other* bits of the
source code that tacitly (and incorrectly) assumed a two's
complement representation.

Mark