How about adding rational fraction to Python?

[Jeff Schwab]

Carl Banks wrote:
> On Feb 16, 5:51 pm, Jeff Schwab <j... at schwabcenter.com> wrote:
>> Carl Banks wrote:
>>> On Feb 16, 3:03 pm, Lie <Lie.1... at gmail.com> wrote:
>>>> Although rationals have its limitations too, it is a much
>>>> better choice compared to floats/Decimals for most cases.
>>> Maybe that's true for your use cases, but it's not true for most cases
>>> in general.
>>> Rationals are pretty useless for almost any extended calculations,
>>> since the denominator tends to grow in size till it's practically
>>> unusbale,
>> What do you mean by "practically unusable?"
> 
> So big that a fraction takes 10 minutes to reduce to simplest form and/
> or your hard disk starts thrashing.
> 
> It can easily happen with seemingly innocuous calculations.
> 
> 
>> I heard similar arguments
>> made against big integers at one point ("Primitive types are usually big
>> enough, why risk performance?") but I fell in love with them when I
>> first saw them in Smalltalk, and I'm glad Python supports them natively.
> 
> It's not the same argument, though.
> 
> Repeated calculations don't make bignums too large to manage unless
> they're growing it exponentially.
> 
> With rationals, the accumulating calculations usually makes the
> denominator grow out of control (unless there's some mitigating
> factor, like in Paul Rubin's example where there were only a ever few
> denominators.)

OK, thanks for explaining.  It doesn't seem to me intuitively like 
something that would be a problem, but I'm willing to take your word for it.