DData

[Simon Marlow]

> JP Bernardy wrote:
> > [...] Therefore, I hereby submit it to the people in charge
> > of the hierarchical libraries, for integration. Of
> > course, if any specific detail deserves work, I remain
> > available. [...]
> 
> I could add DData to the hierarchical libraries in the 
> fptools repository,
> but first a few points should be clarified:

Can we hold off on this a while longer please.  Partly because I am not
here :-) but also I think it needs at least one more round of reviewing,
and there is still Ross's overloaded sequences suggestion to decide on.

The intention was for the DData libraries to be placed directly under
Data (i.e. Data.Set etc.).  I had imagined that we would leave the old
interfaces available too, deprecated, as long as the names didn't clash.

None of this precludes adding overloaded collections later; all we're
doing here is adding some concrete data structures.

Cheers,
	Simon