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Message-ID: <891bd3390608311504g13cf0ea6x2cbb0a79cfd29760@mail.gmail.com>
Date: Thu, 31 Aug 2006 18:04:43 -0400
From: "Yaron Minsky" <yminsky@cs.cornell.edu>
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To: "Caml Mailing List" <caml-list@inria.fr>
Subject: Re: Overriding an entry in a polymorphic variant
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On 8/31/06, Yaron Minsky <yminsky@cs.cornell.edu> wrote:
>
> Does anyone know if there is a clean way of overriding a field in a
> polymorhphic variant.  I want to do something like this:
>
> type bot = [ `bot ]
> type top = [`bot | `top]
> type t = [ `a of bot | `b of bot | `c of bot | `d of bot | `e of bot ]
> type t1 = [ t | `c of top  | `e of top ]
>
> the desired end result being that t1 is actually [ `a of bot | `b of bot |
> `c of top | `d of bot | `e of top ].  I'm hoping to do this largely to
> enable some phantom-types hackery I'm working on.  I'm not sure it matters
> from the point of view of whether this is doable, but it is potentially
> relevant that bot is a subtype of top.
>

Small addendum:  I'm still not sure this is relevant, but I did get my
example slightly backwards.  top should be a subtype of bot, not the other
way.  So the definitions of bot and top should be:

type bot = [ `bot |  `top]
type top = [`top]

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On 8/31/06, <b class="gmail_sendername">Yaron Minsky</b> &lt;<a href="mailto:yminsky@cs.cornell.edu">yminsky@cs.cornell.edu</a>&gt; wrote:<div><span class="gmail_quote"></span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div>Does anyone know if there is a clean way of overriding a field in a polymorhphic variant.&nbsp; I want to do something like this:<br><br>type bot = [ `bot ]<br>type top = [`bot | `top]<br>type t = [ `a of bot | `b of bot | `c of bot | `d of bot | `e of bot ]
<br>type t1 = [ t | `c of top&nbsp; | `e of top ]<br><br>the desired end result being that t1 is actually [ `a of bot | `b of bot | `c of top | `d of bot | `e of top ].&nbsp; I'm hoping to do this largely to enable some phantom-types hackery I'm working on.&nbsp; I'm not sure it matters from the point of view of whether this is doable, but it is potentially relevant that bot is a subtype of top.
</div></blockquote><div><br>Small addendum:&nbsp; I'm still not sure this is relevant, but I did get my example slightly backwards.&nbsp; top should be a subtype of bot, not the other way.&nbsp; So the definitions of bot and top should be:
<br><br>type bot = [ `bot |&nbsp; `top]<br>type top = [`top]<br></div><br></div><br>

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