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