Module Base.Staged

A type for making staging explicit in the type of a function.

For example, you might want to have a function that creates a function for allocating unique identifiers. Rather than using the type:

  val make_id_allocator : unit -> unit -> int

you would have

  val make_id_allocator : unit -> (unit -> int) Staged.t

Such a function could be defined as follows:

  let make_id_allocator () =
    let ctr = ref 0 in
    stage (fun () ->
      incr ctr;
      !ctr)
  ;;

and could be invoked as follows:

  let id1, id2 =
    let alloc = unstage (make_id_allocator ()) in
    alloc (), alloc ()
  ;;

both stage and unstage functions are available in the toplevel namespace.

(Note that in many cases, including perhaps the one above, it's preferable to create a custom type rather than use Staged.)