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.
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