给大佬感受一下OCaml

stack.ml

(* module stack *)
(* 用OCaml的module system 写一个类似C的Stack *)

module type Element = sig
  type t
end

module Stack (Ele : Element)
= struct
  type elementType = Ele.t
  type t = elementType list ref

  let create () = ref []

  let push (tt:t) elem = 
    let _ = tt := elem::!tt
    in ()

  let pop (tt:t) =
    match !tt with
    | first::rest ->
        let () = 
          tt := rest 
        in
        first
    | _ -> failwith "empty"


end


module MyStack = Stack (struct 
  type t = int
end)

let () =

  let stack = MyStack.create () in
  
  MyStack.push stack 1;
  MyStack.push stack 2;

  Printf.printf "%d\n" (MyStack.pop stack);
  Printf.printf "%d\n" (MyStack.pop stack);