Henrik Nilsson wrote:

So, if, in the interest of being conservative, the stated minimal bound cannot be "infinity", could it at least be a great deal bigger than what reasonably would be used in *hand-written* code? Say 15. An arbitrary choice, of course, but it is not excessive from an implementation perspective, yet large enough that I cannot imagine hand-written code getting close to the limit.

A fair point. If you care either way, send me a note. (Not to the list.) Henrik leaves open the question of which tuple *instances* you can rely on. Up to 7, like zip and friends? Or up to 15? By analogy with the zip functions, I think I'd go for 7. Again, let me know, but don't trouble the list unless you want to raise a new point. Simon