PEP239 (Rational Numbers) Reference Implementation and new issues

[Paul Boddie]

"Chris Gonnerman" <chris.gonnerman at newcenturycomputers.net> wrote in message news:<mailman.1033615625.14473.python-list at python.org>...
> 
> But I don't want to see rationals if I haven't asked for
> them.

[...]

> but would it hurt so much to say 
> 
>     1/3R
> 
> instead?

How about the use of specially formed rational literals using the
underscore notation, which I'm sure exists in various other systems?
For example:

  1_3

The standard operators would produce rational results from rational
inputs:

  1_3 + 2 == 7_3
  1_3 - 2 == -5_3
  1_3 / 2 == 1_6
  1_3 * 2 == 2_3

Use of floating point values in such operations would either produce
errors:

  1_3 + 2.5 -> TypeError

Or they could coerce the result to floating point (with the usual
consequences):

  1_3 + 2.5 -> 1.0 / 3.0 + 2.5 == 2.8333333333333335

One would then need to define operators or functions to produce
rationals from other types:

  rational(1, 3) == 1_3
  rational(1)    == 1_1
  rational(1.5)  -> TypeError

And certain built-in functions would need changing:

  int(1_3) == 0
  float(1_3) -> 1.0 / 3.0 == 0.33333333333333331

I'm sure that all this has been discussed over and over again before,
though.

Paul