(From:

http://paddy3118.blogspot.com/2008/0...ons-issue.html)

There seems to be a problem/difference in calculating with the new

fractions module when comparing Python 26rc2 and 30rc1

I was reading the paper "Interval Arithmetic: Python Implementation

and Applications" and thought to try the first example function

f(x,y), which needs more precision than Python floating point provides

(on my Windows PC), to calculate a sensible answer.

Ahah, I thought, lets try this with Fractions - so I first installed

Python 30rc1, typed in the Function - saw the rubbish result, then

used Fractions and got the 'right' result.

I then wondered if fractions had been back-ported to Python 2.6rc2,

found that it had, but got different results.

As you can see from the table, Python 2.6rc2 has a problem calculating

t3 = F(11,2) * y**8 + x/(2*y), where F is Fraction.

I wonder where the problem lies?

(For the Table, please see the blog entry).

- Paddy.