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.)