Thanks Paul and Joseph for the quick replies.
Paul, I do hope that expl3 will provide at least the basics of the  
functions you describe. Indeed, some of them are already there.

On 25/01/2009, at 6:54 AM, Joseph Wright wrote:

> I'd favour sticking with just comma lists (by far the most common  
> type),
> and providing the arbitrary function you describe.  While LaTeX3 is
> supposed to have a good programming base, I'd expect that the
> specialised ideas you suggest are rare enough that they can be handled
> at a module level, not in the kernel.

After a good sleep :) I now agree with you.

Thanks for indulging my rambling.