[Python-Dev] Re: PEP239 (Rational Numbers) Reference Implementation and new issues

[Raymond Hettinger]

From: "Greg Ewing" <greg@cosc.canterbury.ac.nz>
> > The HP32SII calculator implements a useful rational model using
> > flags and a maximum denominator register.  If the first flag is clear,
> > fractions are have denominators upto the maximum value.  If only
> > the first flag is set, fractions always use the maximum denominator
> > as the denominator and are then reduced (i.e. if the max is 8, then
> > .5 is represented as 1/2 and .1 is represented as 1/8).
> 
> I can see that being useful when you're doing calculations
> with, e.g. measurements in 64ths of an inch and you don't
> care if anything smaller than that isn't quite exact.
> 
> But I get the impression that the folks who want rationals
> in Python want them precisely because they're *always*
> exact. If you couldn't rely on them to always be exact,
> it would defeat the purpose.

For that, I propose maxdenom=None to let the rationals
grow without bound.


Raymond Hettinger