OCaml 4.02.3 with modular implicits

gistfile1.txt

module type Show = sig
    type t
    val show : t -> unit
end;;

let print {S : Show} x = S.show x;;

implicit module Show_float = struct
    type t = float
    let show x = Printf.printf "Show_float: %f\n" x
end;;

module Show_list_impl {X : Show} = struct
        type t = X.t list
        let show x =
            Printf.printf "Show_list: [\n";
            List.iter X.show x;
            Printf.printf "]\n%!"
    end;;

implicit module Show_list = Show_list_impl;;

let _ = print [1.;2.5;-3.4];;

implicit module Show_int = struct
    type t = int
    let show x = Printf.printf "Show_int: %d\n" x
end;;

let _ = print [3;5;1];;