random_module.ml

module type T = sig
  type t
  val x: t
  val show: t -> string
end

module Int = struct
  type t = int
  let x = 1
  let show = string_of_int
end

module String = struct
  type t = string
  let x = "one"
  let show = Fun.id
end

let random (): (module T) =
  if Random.float > 0.5 then
    (module String)
  else
    (module Int)