[Haskell-cafe] Re: Positive integers

[Henning Thielemann]

On Fri, 24 Mar 2006, Aaron Denney wrote:

>> Without breaking compatibility?
>> But class instances become invalid if the hierarchy is modified.
>
> No, compatibility will be broken.  Hopefully not for most uses -- I
> don't think most people define new instances, and those that do will be
> able to do so more reasonably, so hopefully wouldn't mind.

There are a lot of instances of Num around. Everywhere where Haskell is 
used as a wrapper to other languages like CSound, SuperCollider, metapost 
new numerical instances are defined. Since restructuring the numerical 
type class hierarchy would break them I assumed that a modified hierarchy 
is out of scope of Haskell'.

> Not at all.  That is one of the things I looked at a while ago, that has
> inspired a lot of my decisions -- but I'm more willing to rename things
> that I think have silly names.  And there are a few minor details, like
> allowing only for euclidean domains rather than principal ideal domains.
>
> I will probably actually put two proposals up, with one allowing more
> generality via MPTCs and FDs (which I truly hope make it into the
> standard).

Whatever you propose for Haskell' feel encouraged to also contribute 
improvements to NumericPrelude.