Hugs Humor

[Derek Elkins]

On Tue, 08 Jul 2003 13:06:23 +0100
Jon Fairbairn <Jon.Fairbairn@cl.cam.ac.uk> wrote:

> On 2003-07-08 at 10:15+0200 Jerzy Karczmarczuk wrote:
> >  > If it's a _Rational_, surely you want it to be exactly the
> >  > same as you get for 31415926536%10000000000?
> > 
> > No. If 'you' means concretely me, then no. Simply no.
> > Writing
> > pi = 3.1415926536 :: Rational
> > 
> > and expecting to continue the computations with an exact fraction
> > 31415926536%10000000000, with the well known explosion of Nums &
> > Dens seems pragmatically silly.
> 
> Ah, well, I'd say that writing
> 
>   pi = 3.1415926536 :: Rational
> 
> is just misleading -- we all know jolly well that pi isn't a
> rational, so anyone who writes that deserves what they get.
> 
> Now, if you were to write
> 
>   pi = 3.1415926536 :: Real
> 
> I'd be happy to argue over just what the conversion is
> supposed to do. Unfortunately we don't have Real (in
> libraries as far as I remember -- if you have a continued
> fraction implementation of it, it ought to go to the
> libraries list).

There's an exact real library in haskell-libs using Linear
Fractional Transformations,
http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/haskell-libs/libs/exactreal/.