Re: [Caml-list] Implicit question about searching for implicit module definition in the functor argument.

[Kakadu <kakadu.hafanana@gmail.com>]

Oh, thanks. I did know that it is something obvious. Maybe we will
need a warnings for this......

On Wed, Aug 3, 2016 at 8:18 AM, Gawlitza, Thomas
<thomas.gawlitza@sap.com> wrote:
> Hi!
>
>
>
> Your question inspired me to have a look at the modular implicits. I really
> like them. It seems that the argument of the implicit functor Show_logic
> also needs to be implicit, i.e., in curly braces. At least this worked for
> me.
>
>
>
> Thomas
>
>
>
> module type SHOW = sig
>
>     type t
>
>     val show : t -> string
>
> end
>
>
>
> let show {S : SHOW} x = S.show x;;
>
>
>
> implicit module Show_int : (SHOW with type t = int) = struct
>
>     type t = int
>
>     let show = string_of_int
>
> end
>
>
>
> module type CORE = sig
>
>   type 'a logic
>
>
>
>   implicit module Show_logic {X: SHOW} : (SHOW with type t = X.t logic)
>
> end
>
>
>
> module Make(MK: CORE) = struct
>
>   open MK
>
>   (* open implicit MK (* doesn't help *) *)
>
>
>
>   let foo (x: int logic) =
>
>     let s = show x in (* Error: No instance found for implicit S. *)
>
>     s
>
> end
>
>
>
>
>
> ---
>
>
>
> Dr. rer. nat. Thomas Martin Gawlitza, Diplom-Informatiker
>
> Development Architect
>
> Technology Office
>
> office location: Potsdam (DE), POT04, A2.01, SAP Innovation Center,
> Konrad-Zuse-Ring 10, 14469 Potsdam
>
> email: Thomas.Gawlitza@sap.com
>
> phone: +49 331 9799 5408
>
> mobile: +49 151 168 10 726
>
>
>
> From: <caml-list-request@inria.fr> on behalf of Kakadu
> <kakadu.hafanana@gmail.com>
> Reply-To: Kakadu <kakadu.hafanana@gmail.com>
> Date: Wednesday 3 August 2016 at 01:17
> To: Caml List <caml-list@inria.fr>
> Subject: [Caml-list] Implicit question about searching for implicit module
> definition in the functor argument.
>
>
>
> Hey, hackers.
>
>
>
> I'm missing something obvious. Any fresh eyes around?
>
>
>
> module type SHOW = sig
>
>     type t
>
>     val show : t -> string
>
> end
>
>
>
> let show {S : SHOW} x = S.show x;;
>
>
>
> implicit module Show_int : (SHOW with type t = int) = struct
>
>     type t = int
>
>     let show = string_of_int
>
> end
>
>
>
> module type CORE = sig
>
>   type 'a logic
>
>
>
>   implicit module Show_logic(X: SHOW) : (SHOW with type t = X.t logic)
>
> end
>
>
>
> module Make(MK: CORE) = struct
>
>   open MK
>
>   open implicit MK (* doesn't help *)
>
>
>
>   let foo (x: int logic) =
>
>     let s = show x in (* Error: No instance found for implicit S. *)
>
>     s
>
> end
>
>
>
>
>
> Kind regards,
>
> Kakadu
>
>
>
> --
>
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