> >   let rec combs = function
> >
> >       | (0, _) -> [[]]
> >       | (n, es) when n > List.length es -> []
> >       | (n, e::es) -> List.map (fun l -> e::l) (combs (n-1, es)) @ combs
> >       | (n, es)
> >
> >   let triplets es = combs (3, es)
> >
> > Question to the rest of the list:  The ocaml compiler complains with
> >   ...
> >   Warning P: this pattern-matching is not exhaustive.
> >   Here is an example of a value that is not matched:
> >   (1, [])
> >   (However, some guarded clause may match this value.)

Personally, if you know it can never be reached, then an assertion is
probably better.

| otherwise -> assert false (* I prefer using a name like otherwise
rather than _ for pure readability value *)

Jonathan