An Obj.magic tutorial

magic.ml

(* An Obj.magic tutorial. *)

(* Start with a function that does some integer computation *)
let f _ _ _ _ _ =
  42_42_42_42+42_42_4-2_42

(* We're going to use OCaml's "magic increment" *)
let i = Obj.magic incr

let _ =
  let f = ref f and g = ref f in
  (* Increment f 9 times until we get the desired
     function: in this case, print_string *)
  i f; i f; i f;
  i f; i f; i f;
  i f; i f; i!f;
  (* Now we can print things! *)
  ! g () () () "Hello, magic world!\n" 10