open Effect
open Effect.Deep

module type Console = sig
  val read : unit -> string
  val write : string -> unit
end

type _ Effect.t += Console : (module Console) t

let ask () = perform Console

let main () =
  let module Console = (val ask ()) in
  Console.write "enter your name:";
  let name = Console.read () in
  Console.write ("Hello, "^name)

(*****)

let handler f = match f () with
  | effect Console, k -> continue k (module struct
      let read = read_line
      let write = print_endline
  end)
  | ret -> ret

let _ = handler main