Re: Question about GADT

I'm trying to unwrap the data built with "data_int" or "data_string". Ie 
i'm trying to retrieve the original value "v" used in "data_int" or 
"data_string" but only by using the "to_ocaml_value" function. I don't 
even know if it's possible?

On 03.12.2015 23:42, Gabriel Scherer [email protected] 
[ocaml_beginners] wrote:
> The program has a type error, as (v) in the last sentence could be
> either (Int n) or (String s). The compiler is right to complain. What
> are you trying to do?
>
> On Thu, Dec 3, 2015 at 11:34 PM, Stephane Legrand [email protected]
> [ocaml_beginners] <[email protected]> wrote:
>  > Hello,
>  >
>  > I'm trying to run the code below. The compiler gives me an error for the
>  > "print_endline x" line: "This expression has type ex#0 but an expression
>  > was expected of type string". Is there a way to fix this error? If this
>  > kind of thing is doable with GADT? Thank you.
>  >
>  > type _ data =
>  > Int : int -> int data
>  > | String : string -> string data
>  >
>  > type t =
>  > Wrap : _ data -> t
>  >
>  > let data_int v = Wrap(Int v)
>  > let data_string v = Wrap(String v)
>  >
>  > let to_ocaml_value : type a. a data -> a = function
>  > | Int v -> v
>  > | String v -> v
>  >
>  > let test = data_string "test"
>  >
>  > let () =
>  > match test with
>  > | Wrap v ->
>  > let x = to_ocaml_value v in
>  > print_endline x
>  >
>  >
>  > Regards,
>  > Stéphane.
>  >
>  >