Improve documentation for Real

[Ben Franksen]

Am 24.12.20 um 03:46 schrieb David Feuer:
> Wouldn't it make more sense to get at the idea from another direction or
> two? One obvious idea is to compare to a rational number:
> 
>     compareRational :: a -> Rational -> Ordering
> 
> Neither this nor Ord can be supported by computable reals,

Disclaimer: I have only a vague idea what computable reals are, which
may explain why this is totally non-obvious to me!

I mean, for Ord: yes, I do understand ahy this is not computable, but
compareRational? Could you post a pointer or reference?

Cheers
Ben