> Hashtables are mutable objects. What happens if 
> I iterate over a hashtable, applying Hashtble.remove
> to (some of) the elements? Will this work? 

It will work in the sense that nothing will crash and you hashtable
will remain in a consistent state.  However, some of the (key,data)
pairs you removed with Hashtbl.remove may still be presented later to
your iterated function.

- Xavier Leroy