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Date: Wed, 07 Jul 2004 10:53:16 +0900 (JST)
Message-Id: <20040707.105316.68550622.garrigue@kurims.kyoto-u.ac.jp>
To: szegedy@t-online.de
Cc: caml-list@inria.fr
Subject: Re: [Caml-list] Polymorphic method problem
From: Jacques GARRIGUE <garrigue@kurims.kyoto-u.ac.jp>
In-Reply-To: <40EAEE20.2010805@t-online.de>
References: <40EAEE20.2010805@t-online.de>
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From: szegedy@t-online.de (Christian Szegedy)

> Can anyone tell me, why does the following piece of
> code fail to compile, and how can I achieve
> equivalent effect in the most convenient way?
> 
> class a () =
>    object(self)
>       method f : 'a. ((< f : unit; .. > as 'a) -> unit) = fun other -> 
> other#f 
>       method g = (self :> a)
>    end

There was a bug in the subtyping algorithm.
Hopefully, it's now fixed in CVS.

A workaround at the source level is to define your type in advance:

class type ta = object
  method f : <f : unit; ..> -> unit
  method g : ta
end
class a () =
  object(self : #ta)
    method f other = other#f
    method g = (self :> ta)   
  end

Jacques Garrigue

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