is_this_fcm.ml

module type Show = sig
  type t
  val show: t -> string
end
let show (module S: Show) v = S.show v

module Show_option (S: Show) = struct
  type t = S.t option
  let show v =
    match v with
    | None -> "None"
    | Some v -> Printf.sprintf "(Some %s)" (S.show v)
end
let x = show (
  if Random.float(1.0) > 0.01 then
    (module Show_option(struct 
      type t = int
      let show = Printf.sprintf "%d"
    end))
  else
    (module Show_option(struct
      type t = int
      let show v = Printf.sprintf "%d" (v - 1)
    end))
)