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|
(* TEST
* toplevel
*)
(* simple printer *)
type t = A | B;;
let print_t out t =
Format.fprintf out "%s"
(match t with
| A -> "~A"
| B -> "~B"
);;
#install_printer print_t;;
type u = C of t;;
B;;
C B;;
(* old-style printer *)
type old = OA | OB;;
let print_old = function
| OA -> Format.printf "Old(A)"
| OB -> Format.printf "Old(B)"
;;
#install_printer print_old;;
[OA; OB];;
#remove_printer print_old;;
[OA; OB];;
(* genreic printers *)
type ('a, 'b) v = D of 'a * 'b;;
type 'a printer = Format.formatter -> 'a -> unit;;
let print_generic (type a b) (pa : a printer) (pb : b printer) : (a, b) v printer =
fun ppf (D (a, b)) ->
Format.fprintf ppf "D<%a, %a>"
pa a
pb b
;;
#install_printer print_generic;;
[D (0, A); D (42, B)];;
(* error cases *)
#install_printer name_that_does_not_exist;;
#install_printer List.map;;
#remove_printer name_that_does_not_exist;;
#remove_printer List.map;;
let non_installed_printer ppf () = ();;
#remove_printer non_installed_printer;;
|
