On Fri, Sep 22, 2017 at 8:37 AM, Guido van Rossum <gu...@python.org> wrote:
> On Thu, Sep 21, 2017 at 9:20 PM, Nick Coghlan <ncogh...@gmail.com> wrote: > >> >>> one_tenth = 0x1.0 / 0xA.0 >> >>> two_tenths = 0x2.0 / 0xA.0 >> >>> three_tenths = 0x3.0 / 0xA.0 >> >>> three_tenths == one_tenth + two_tenths >> False >> > > OMG Regardless of whether we introduce this feature, .hex() is the way to > show what's going on here: > > >>> 0.1.hex() > '0x1.999999999999ap-4' > >>> 0.2.hex() > '0x1.999999999999ap-3' > >>> 0.3.hex() > '0x1.3333333333333p-2' > >>> (0.1+0.2).hex() > '0x1.3333333333334p-2' > >>> > > This shows so clearly that there's 1 bit difference! > Thanks! I really should add this example to the math.isclose() docs.... .hex is mentioned in: https://docs.python.org/3/tutorial/floatingpoint.html but I don't see it used in a nice clear example like this. -CHB > > > -- > --Guido van Rossum (python.org/~guido <http://python.org/%7Eguido>) > > _______________________________________________ > Python-ideas mailing list > Python-ideas@python.org > https://mail.python.org/mailman/listinfo/python-ideas > Code of Conduct: http://python.org/psf/codeofconduct/ > > -- 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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