What's the best way to do this?

I was thinking of forcing the first few elements of a lazy list before pattern 
matching and then looking for forced values in the lists as patterns but I 
don't think you can deconstruct a lazy value in a pattern match...

-- 
Dr Jon D Harrop, Flying Frog Consultancy Ltd.
The OCaml Journal
http://www.ffconsultancy.com/products/ocaml_journal/?e