On Sat, 28 Nov 2009 15:14:31 -0800, Mark Dickinson wrote: >> 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.
I don't think that really has any bearing on the Original Poster's question -- presumably on such machines, Python should treat both -0 and +0 as false in a boolean context and generate the same result. When it comes to integers, I'm not aware of any mathematical or programming system which treats -0 and +0 as distinct entities, even if they have different internal representations. But the same doesn't apply for floats, where the IEEE standard requires that -0.0 and +0.0 be distinct and distinguishable (although it also requires that they compare as equal). -- Steven -- http://mail.python.org/mailman/listinfo/python-list
