Ptr.ml

Ptr.ml

module Ptr = struct
  type 'a t

  external create : 'a -> 'a t = "%makemutable"
  external get_value : 'a t -> 'a = "%field0"
  external of_ref : 'a ref -> 'a t = "%identity"

  let of_int : int -> 'a t = function
    | i -> Obj.magic (i / 2)
  ;;

  let to_int : 'a t -> int = function
    | ptr -> 2 * Obj.magic ptr
  ;;

  let null () : 'a t = Obj.magic 0

  module Notation = struct
    let ( ~& ) = create
    let ( ~* ) = get_value
  end
end

open Ptr.Notation

(* *)
let x = 65
let y = x |> ref |> Ptr.of_ref
let () = assert (~*y = x)
let () = Printf.printf "%#x\n" (Ptr.to_int y)