Math errors in python

Andrea Griffini agriff at tin.it
Mon Sep 20 07:56:08 CEST 2004


On 19 Sep 2004 15:24:31 -0700, danb_83 at yahoo.com (Dan Bishop) wrote:

>Also, the
>IEEE 754 double-precision representation of pi is equal to the
>rational number 4503599627370496/281474976710656.

I know the real uses of a precise pi are not that many... but
isn't that a quite raw approximation ? that fraction equals 16...

>Base 10 _is_ more accurate for monetary amounts, and for this reason I
>agreed with the addition of a decimal class.  But it would be a
>mistake to use decimal arithmetic, which has a performance
>disadvantage with no accuracy advantage, in the general case.

For monetary computation why not using fixed point instead
(i.e. integers representing the number of thousands of cents,
for example) ? IMO using floating point instead of something
like arbitrary precision integers is looking for trouble in
that area as often what is required is accuracy up to a
specified fraction of the unit.

Andrea

PS: From a study seems that 75.7% of people tends to believe
    more in messages that contain precise numbers (like 75.7%).



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