(* Newer version of an imagined data format. Compare to `format_v1.atd'. *)

type t = {
  a : int option;
  (* removed field b, making newer data unreadable with older software since
     b was not optional. *)
  ?c : int option;
  ~d : float;
  ~e : string list; (* added optional field e, allowing newer software
                       to read older data. *)
}