Data.* collections maintenance

[Ross Paterson]

On Fri, Oct 21, 2005 at 05:15:54PM +0200, Georg Martius wrote:
> Why not having a class for Set and Map,... and then we can change the 
> implementation in the instances. Furthermore we could specify optimised 
> versions like IntMap as an instance.

One class or two, one hierarchy or two?  There are several proposals
(see this list in Mar and Apr last year), but none is ideal, and they
all need multi-parameter type classes.