How about adding rational fraction to Python?

M.-A. Lemburg mal at egenix.com
Mon Feb 25 10:56:29 CET 2008


If you're interested in rationals, then you might want to have a look
at mxNumber which is part of the eGenix mx Experimental
Distribution:

http://www.egenix.com/products/python/mxExperimental/mxNumber/

It provides fast rational operations based on the GNU MP
library.

On 2008-02-25 07:58, Carl Banks wrote:
> On Feb 24, 10:56 pm, Mensanator <mensana... at aol.com> wrote:
>> But that doesn't mean they become less manageable than
>> other unlimited precision usages. Did you see my example
>> of the polynomial finder using Newton's Forward Differences
>> Method? The denominator's certainly don't settle out, neither
>> do they become unmanageable. And that's general mathematics.
> 
> No, that's a specific algorithm.  That some random algorithm doesn't
> blow up the denominators to the point of disk thrashing doesn't mean
> they won't generally.
> 
> Try doing numerical integration sometime with rationals, and tell me
> how that works out.  Try calculating compound interest and storing
> results for 1000 customers every month, and compare the size of your
> database before and after.

It is well possible to limit the denominator before storing it
in a database or other external resource using Farey neighbors:

http://en.wikipedia.org/wiki/Farey_sequence#Farey_neighbours

mxNumber implements an algorithm for this (not the most efficient
one, but it works nicely).

-- 
Marc-Andre Lemburg
eGenix.com

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