Sorry, again...

What is the difference beteen the functor F and the function f ?
(F is not typable, but f is)

module F(X:sig  
  type t = private [< `A | `B | `C ]
  val f : [`III ] -> t end) = 
  struct
    let rec g  = function
	[] -> []
      | `I  :: tl -> `A :: (g tl)
      | `II :: tl -> `B :: (g  tl)
      | (`III as iii) :: tl  -> 
	  let iii' = (X.f iii : [< `A | `B | `C ] :> [> `A | `B ]) in
	  iii' :: (g tl)
  end


let f (x : [< `A | `B | `C]) = (x : [< `A | `B | `C] :> [> `A | `B]);;

I also curious to know whether there is a way to 
make g's type depend on X.t in 

module G(X:sig type t = private [< `A ] val f : int -> t end) = struct
  let g x = if x = 0 then `B else X.f x 
end


Regards, 
Keiko NAKATA