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

[François Pinard]

[Guido van Rossum]

>> But _maybe_ it could be more tractable at the lexical level without
>> bringing too much confusion, and for numerical _constants_ only -- 3:2 is
>> one number, has never been two.
>
> I think the slice notation e.g. x[1:4] kills that idea.

And it kills it dead indeed, at least, in my opinion.

[M.-A. Lemburg]

> Are you sure that you really want a special syntax for this
> rather than just a simply constructor like rat(2,3) ?

This is what I currently do whenever I need rationals.  It might not be as
elegant as the `:' would have been, but it works well in practice.  I guess
I would prefer ^rat(2, 3)" over any non-elegant or non-natural notation for
rational constants.  We do not necessarily ought to have a special notation
hardwired in Python syntax.

If Guido was adding complex numbers today instead of long ago, I wonder if
he would allow a special notation for them, or just suggest a constructor.

> Note that intution isn't going to help here because you are missing a
> precision indicator.  mxNumber has a constructor called FareyRational()
> which converts floats to rationals: [...]

Interesting, I'll save it.  I use continued fraction expansion to get the
"best" rational fitting a float within a tolerance, and wonder how Farey
will be similar/different.  Tim will surely tell us, out of his head! :-)

-- 
François Pinard   http://www.iro.umontreal.ca/~pinard