Does anyone have any ideas or references on how the union/inter/diff functions 
of the Set module could be optimised by accepting a sequence of sets rather 
than a pair at a time? For example, if A overlaps B overlaps C but A does not 
overlap C then it is probably quicker to compute the union "(A U C) U B" 
rather than "A U B U C".

Better still, does anyone have a replacement Set module which implements this 
functionality?

-- 
Dr Jon D Harrop, Flying Frog Consultancy Ltd.
Objective CAML for Scientists
http://www.ffconsultancy.com/products/ocaml_for_scientists