Dylan Thurston wrote:
I've started writing up a more concrete proposal for what I'd like the Prelude to look like in terms of numeric classes.
I like this proposal a lot. The organization is closer to traditional mathematical structures than the current Prelude, but not as intimidating as Mechveliani's Basic Algebra Proposal. A very nice balance, IMO. A couple of requests:
module Lattice where class Lattice a where meet, join :: a -> a -> a
Could this be split into class SemiLattice a where join :: a -> a -> a and class (SemiLattice a) => Lattice a where meet :: a -> a -> a I run across a lot of structures which could usefully be modeled as semilattices, but lack a 'meet' operation.
It would be reasonable to make Ord a subclass of this, but it would probably complicate the class heirarchy too much for the gain.
In a similar vein, I'd really like to see the Ord class split up: class PartialOrder a where (<), (>) :: a -> a -> Bool class (Eq a, PartialOrder a) => Ord a where compare :: a -> a -> Ordering (<=), (>=) :: a -> a -> Bool max, min :: a -> a -> a Perhaps it would make sense for PartialOrder to be a superclass of Lattice? --Joe English jenglish@flightlab.com