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.