Re: [Caml-list] About polymorphic methods and recursive classes

[Damien <Damien.Pous@ens-lyon.fr>]

On Sat, 22 Mar 2003 12:22:44 +0100
Sébastien Briais <sebastien.briais@epfl.ch> wrote:

> Hello,
hello

> # class virtual ['a] visitor =
>    object
>      method virtual caseNil : 'a
>    end
>    and virtual int_list =
>    object
>      method virtual visit : 'a.('a visitor -> 'a)
>    end
>    ;;
> class virtual ['a] visitor : object method virtual caseNil : 'a end
> class virtual int_list : object method virtual visit : 'a visitor ->
> 'a end
> 
> # class nil =
>    object
>      inherit int_list
>      method visit v = v#caseNil
>    end
>    ;;
> This expression has type 'a visitor
> It has no method caseNil

it seems to work with class types :

#   class type ['a] visitor_t = object 
	method caseNil: 'a 
end;;
  class type ['a] visitor_t = object method caseNil : 'a end

# class type int_list_t = object 
	method visit: 'a. ('a visitor_t) -> 'a
end;; 
  class type int_list_t = object method visit : 'a visitor_t -> 'a end

# class nil: int_list_t = object
  method visit: 'a. ('a visitor_t) -> 'a = fun v -> v#caseNil
end;;
      class nil : int_list_t


damien

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