Re: Question about GADT

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.
>
>
> ------------------------------------
> Posted by: Stephane Legrand <[email protected]>
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