[Haskell-cafe] Re: Why does the class called "Real" support only rationals, and not all reals?

Henning Thielemann lemming at henning-thielemann.de
Tue Jun 5 06:47:23 EDT 2007

On Mon, 4 Jun 2007, Dan Piponi wrote:

> On 6/4/07, DavidA <polyomino at f2s.com> wrote:
> > Yes, I'm afraid that you are understanding correctly. Annoying isn't it.
> >
> > It is well-known (among Haskell mathematicians at least) that the numeric type
> > classes in the prelude are broken.
> A few days ago I found myself forced to write:
> > instance Floating Fixed where ...
> where 'Fixed' is a fixed point arithmetic class! :-)
> When you find yourself having to make a type an instance of the
> complete 'opposite' class you know you have serious problems!

Indeed. The corresponding class is called Transcendental in
NumericPrelude. (And FixedPoint is an instance of it.)

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