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Message-ID: <49B147F7.4090303@ens-lyon.org>
Date: Fri, 06 Mar 2009 16:57:43 +0100
From: Samuel Mimram <samuel.mimram@ens-lyon.org>
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To: caml-list@yquem.inria.fr
Subject: Objects and variants
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X-Spam: no; 0.00; ens-lyon:01 variants:01 parametrize:01 cheers:01 unbound:01 unbound:01 compile:01 constraint:01 inferred:02 variables:02 binding:02 objects:02 seems:03 unit:03 unit:03 

Hi,

When I try to compile the following code:

class a =
object
  method f (x:[>]) = ()
end

I get the following error:

Error: Some type variables are unbound in this type:
         class a : object method f : [>  ] -> unit end
       The method f has type ([>  ] as 'a) -> unit where 'a is unbound

Is the binding of [>] to 'a really necessary here? In particular it is
not mentioned in the inferred type...

Of course I can parametrize the class over 'a as

class ['a] a =
object
  method f (x:[>] as 'a) = ()
end

which now has type

class ['a] a : object constraint 'a = [>  ] method f : 'a -> unit end

But this seems rather cumbersome. Is there a way to handle this without
mentioning 'a?

Thanks!

Cheers,

Samuel.