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Re: python math problem

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On Fri, 15 Feb 2013 15:23:29 -0500, Kene Meniru <Kene.Meniru@illom.org>
declaimed the following in gmane.comp.python.general:

> Joel Goldstick wrote:
> 
> > 
> > This is not a string, it is scientific notion for 1.53... times 10 to the
> > -15th power.  Because of rounding errors caused by doing floating point
> > math on in binary, you get a very small number instead of 0.
> > 
> 
> I was just doing some testing and it was not equating to zero. Perhaps if I 
> rounded it up I may be more successful.

	Classical CompSci teachings when working with floating point numbers
is to NEVER compare for equality. Instead one should compare against
some epsilon:

	if x == y:	#don't do

	if abs(x - y) < epsilon:	#do this

	In your situation, "y" would be 0.0, so the test condenses to

	if abs(x) < epsilon:

and a possible epsilon may be 1.0E-14

-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
        wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

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Re: python math problem Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-02-15 17:25 -0500
  Re: python math problem Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-02-16 15:49 +1100
    Re: python math problem Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2013-02-16 13:56 -0500

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