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

M.-A. Lemburg mal@lemburg.com
Thu, 03 Oct 2002 17:27:10 +0200

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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