> On Jun 22, 2016, at 7:59 AM, Grant Edwards <grant.b.edwa...@gmail.com> wrote: > >> On 2016-06-22, Random832 <random...@fastmail.com> wrote: >>> On Wed, Jun 22, 2016, at 10:19, Grant Edwards wrote: >>> >>> Is that guaranteed by Python, or just a side-effect of the >>> implementation? Back in the days when Python used native C >>> integers I think the latter. >> >> AIUI, native C integers have never reliably supported signed zero >> even with representations that naively seem to have it. There's no >> well-defined way to detect it - no int version of copysign, for >> instance - and implementations are free to erase the distinction on >> every load/store or define one of them to be a trap representation. > > It's been almost 25 years since I used hardware that supported signed > zero integers (CDC 6600). I don't recall there being a C compiler > available. We used Pascal and assembly, though I think FORTRAN was > what most people used. I don't recall whether the Pascal > implementation exposed the existence of -0 to the user or not.
When I took mathematics in college, the following was true: -1 * 0 = 0 I would probably have gotten rapped on the knuckles by my instructors if I answered -0. Zero was zero. No plus or minus about that. No discussion of signed integers ever mentioned signed zero. Did I miss something in college? Or did -0 represent zero volts on the negative rail of an op-amp in electronics? Thank you, Chris R. -- https://mail.python.org/mailman/listinfo/python-list
