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typing problem with sexplib and mutually recursive polymorphic types
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Date: 2009-03-11 (14:32)
From: Yitzhak Mandelbaum <yitzhakm@C...>
Subject: Re: [Caml-list] typing problem with sexplib and mutually recursive polymorphic types
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:


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

> On Wed, Mar 11, 2009 at 02:11, yoann padioleau <>  
> 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         
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Yitzhak Mandelbaum