On Fri, Feb 24, 2017 at 6:43 PM, Nathaniel Smith <n...@pobox.com> wrote:
> On Feb 24, 2017 5:29 PM, "David Mertz" <me...@gnosis.cx> wrote: > > Marc-André slightly misspelled the recent-ish addition of math.isclose(), > but I agree that it is absolutely where a "nextafter" belongs. > > > My 2c: I disagree -- numerical tolerance based closeness is fundamentally > different than floating point representation based closeness > agreed -- isclose() is a convenience function to provide folks a way to "do a reasonable thing" without delving into floating point representation issues, etc. INdeed, essentially the same approach could be used for Decimal and Fraction, though they aren't supported by math.isclose() due to the math module being written in C, and the rest of math being all about floats. It's also a little weird to jump from nextafter to isclose, since AFAIK > they have pretty much non-overlapping use cases... > Exactly -- and you can tell by this this thread that confusion is easy with this stuff -- putting them together will only sow more confusion. "Floating Point is Hard" Note how many really smart people on this list say things like " I'm no expert in numerical analysis.. " * nextafter > * a function for counting the number of ulps between two floats > * a function for checking that two floats differ by at most N ulps > > I'm not enough of an expert on numerical analysis to have an opinion on > how useful these would be for Python itself. They certainly are part of a > complete IEEE754 implementation, and useful for exploring the details of > how floats work, if nothing else. > I think there is little question that these are useful for numerical analysis. I think the question is if enough people want to use Python for that kind of analysis to add it to the stdlib. My tendency is to say yes -- if someone wants to write the code, it shouldn't be that hard to maintain -- it's mostly going to be calls to the underlying C lib, yes? -CHB -- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception chris.bar...@noaa.gov
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