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

[M.-A. Lemburg]

Guido van Rossum wrote:
>>But those feelings are no proof of anything.  How do we get the
>>confirmation that using rationals in Python would be easy going and
>>innocuous in practice, beforehand?
> 
> 
> By adding them to the language but as an isolated type.  The right
> conversions should happen when you mix rationals with other types of
> numbers (int/long -> rational -> float -> complex), but no operations
> should return rationals unless a rational goes in.

+1

Note that I started to work on mxNumber to get a feeling for
how well rationals et al. fit the existing world. Turns out
that having separate types is a goog thing. Here's the
coercion scheme I'm using:

                  mx.Number.Float
                        ^
                        |
        --------> Python float
       |                ^
       |                |
       |         mx.Number.Rational
       |                ^
       |                |
Python long --> mx.Number.Integer
       ^                ^
       |                |
        --------  Python integer

-- 
Marc-Andre Lemburg
CEO eGenix.com Software GmbH
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