type _ complist =
    One : ('a -> 'b) -> ('a * 'b) complist
  | Cons : ('a -> 'b) * ('b * 'c) complist -> ('a * 'c) complist

let rec clength : type a . a complist -> int = function
  | One _ -> 1
  | Cons (_, xs) -> 1 + clength xs

let rec ccompose : type a b . (a * b) complist -> (a -> b) = function
  | One f -> f
  | Cons (f, xs) -> (fun x -> ccompose xs (f x))


let f1 (x : int) = x + 1

let f2 (x : int) = string_of_int x

let f3 (x : string) = "It's over " ^ x

let clist = Cons (f1, Cons (f2, One f3))

let _ =
  print_int (clength clist);
  print_newline ();
  print_endline (ccompose clist 8999);;

(* prints
3
It's over 9000 *)