Ocaml中是否有单例变体的用例？

(* Singleton 模块 *)
module Singleton = struct
  (* 私有状态 *)
  type state = {
    value : int;
  }

  (* 创建一个新的实例 *)
  let create_instance () =
    { value = 0 }

  (* 获取实例的值 *)
  let get_value instance =
    instance.value

  (* 设置实例的值 *)
  let set_value instance new_value =
    { instance with value = new_value }
end

(* 使用单例模块 *)
let () =
  let instance = Singleton.create_instance () in
  let value = Singleton.get_value instance in
  let new_instance = Singleton.set_value instance 42 in
  let new_value = Singleton.get_value new_instance in
  print_endline ("Instance value: " ^ string_of_int value);
  print_endline ("New instance value: " ^ string_of_int new_value)