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From: Yitzhak Mandelbaum <yitzhakm@CS.Princeton.EDU>
To: Markus Mottl <markus.mottl@gmail.com>
Cc: yoann padioleau <padator@wanadoo.fr>,
	Caml-list List <caml-list@inria.fr>
Subject: Re: [Caml-list] typing problem with sexplib and mutually recursive  polymorphic types
Date: Wed, 11 Mar 2009 10:32:26 -0400	[thread overview]
Message-ID: <6D1EF1C5-3561-4D45-AE32-48F80EC84E58@cs.princeton.edu> (raw)
In-Reply-To: <f8560b80903110720u1e13b13fm1324f422c910a2fe@mail.gmail.com>

While I'm not sure it will help you in this case (because the code is  
generated), I should note that type *inference* for polymorphic  
recursion is undecidable, but type *checking* is not. Moreover, its  
pretty easy to do in OCaml (if a bit clunky).

An earlier discussion on this list covered a number of ways to do it.  
Here's one:

http://groups.google.com/group/fa.caml/msg/d85e3f62dd52d365

Cheers,
Yitzhak


On Mar 11, 2009, at 10:20 AM, Markus Mottl wrote:

> On Wed, Mar 11, 2009 at 02:11, yoann padioleau <padator@wanadoo.fr>  
> wrote:
>> Yes on this example, but what if I can't move it out because
>> the types really need to be mutually recursive ?
>
> I'm afraid, I don't see any straightforward way of achieving this
> goal.  If the above were allowed in a truly recursive way, you'd
> essentially end up with polymorphic recursion, which is undecidable.
>
> Regards,
> Markus
>
> -- 
> Markus Mottl        http://www.ocaml.info         
> markus.mottl@gmail.com
>
> _______________________________________________
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-----------------------------
Yitzhak Mandelbaum




  reply	other threads:[~2009-03-11 14:32 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-03-11  2:45 Yoann Padioleau
2009-03-11  4:25 ` [Caml-list] " Markus Mottl
2009-03-11  6:11   ` yoann padioleau
2009-03-11 14:20     ` Markus Mottl
2009-03-11 14:32       ` Yitzhak Mandelbaum [this message]
2009-03-11 14:44         ` Markus Mottl
2009-03-11 16:16           ` Damien Doligez
2009-03-11 16:43             ` Markus Mottl
2009-03-11 19:03               ` Till Varoquaux
2009-03-12  1:42               ` Jacques Garrigue
2009-03-11 23:08         ` Yoann Padioleau

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