Hi,

> The dual of sums is products.  Open (labelled) sums
> are "polymorphic variants".  Their duals are open
> (labelled) products are "rows" (which O'Caml already
> supports, through its objects).

Yes, as I mentioned, for some classes of this particular problem the object
system can be put to good use -- when there is a clear tree for inheritance,
for example.  Unfortunately that is always not the case; there are problems
where you would end up with a tangled web of multiple inheritances just for
the sake of avoiding duplicating methods.

Cheers,
Dario