execute.ml

(*
 * exec evaluates the first element of the schedule stream. Because of memoization, this means that
 * whenever we evaluate 'front',  we guarantee that all operations are already memoized.
 *)
let exec ({ front; rear; schedule }: 'a realTimeQueue) =
  match schedule with
    | lazy (StreamCell (_, rest_schedule)) ->
      { front; rear; schedule = rest_schedule }
    (* Due to invariants, this means that |rear| > |front|  *)
    | lazy Nil ->
      (* Now newFront = front @ (rev rear) *)
      let newFront = rotate {front; rear; schedule = Stream.empty} in
      {front = newFront; rear = []; schedule = newFront}
;;