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Subject: Re: [Caml-list] class type param constraint
From: Radzevich Belevich <radzevich.belevich@gmail.com>
To: Jacques Garrigue <garrigue@math.nagoya-u.ac.jp>
Cc: caml-list@inria.fr
In-Reply-To: <20090409.191306.169484516.garrigue@math.nagoya-u.ac.jp>
References: <1239266526.2787.5.camel@serphost.localdomain>
	 <20090409.191306.169484516.garrigue@math.nagoya-u.ac.jp>
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Date: Thu, 09 Apr 2009 14:21:21 +0400
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X-Spam: no; 0.00; subtyping:01 2009:98 wrote:01 caml-list:01 constraint:01 constraint:01 arbitrary:02 confusing:02 garrigue:03 jacques:03 converted:04 thu:05 indeed:07 target:91 mean:08 

On Thu, 2009-04-09 at 19:13 +0900, Jacques Garrigue wrote:
> This may be a bit confusing, but the .. in your constraint on 'c means
> that no actual subtyping will occur when you use this type as target.
> Indeed, if the constraint was left unchanged, it would mean that by
> choosing an arbitrary instance, you could use the as_c method to
> convert an object of type "t a" to any "t".
Why it can't be converted to any valid "t"?