On Fri, Sep 22, 2017 at 8:37 AM, Guido van Rossum guido@python.org wrote:
On Thu, Sep 21, 2017 at 9:20 PM, Nick Coghlan ncoghlan@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
> >
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