On Mon, Mar 12, 2018, 3:25 PM Tim Peters <tim.pet...@gmail.com> wrote:
> [David Mertz <me...@gnosis.cx>] > > ... > > I can see no sane reason why anyone would ever call float.is_integer() > > actually. That should always be spelled math.isclose(x, int(x)) because > > IEEE-754. Attractive nuisance is probably too generous, I'd simply call > the > > method a bug. > > Sometimes it's necessary to know, and especially when _implementing_ > 754-conforming functions. For example, what negative infinity raised > to a power needs to return depends on whether the power is an integer > (specifically on whether it's an odd integer): > > >>> (-math.inf) ** 3.1 > inf > Weird. I take it that's what IEEE-754 says. NaN would sure be more intuitive here since inf+inf-j is not in the domain of Reals. Well, technically neither is inf, but at least it's the limit of the domain. :-). >>> (-math.inf) ** 3.0 # NOTE THIS ONE > -inf > >>> (-math.inf) ** 2.9 > inf > > But, ya, for most people most of the time I agree is_integer() is an > attractive nuisance. People implementing math functions are famous > for cheerfully enduring any amount of pain needed to get the job done > ;-) >
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