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Date: Thu, 16 Dec 2004 17:38:46 -0500
From: John Prevost <j.prevost@gmail.com>
Reply-To: John Prevost <j.prevost@gmail.com>
To: Alex Baretta <alex@barettadeit.com>
Subject: Re: [Caml-list] Dummy polymorphic constructors
Cc: Ocaml <caml-list@inria.fr>
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On Thu, 16 Dec 2004 20:22:57 +0100, Alex Baretta <alex@barettadeit.com> wrote:
> Currently ocaml does not support empty polymorphic variant sum types.
> Say, I cannot write the following.
> 
> type empty = [ ]
> 
> This fails due to a syntax error rather than a typing error, which is a
> sensible, given that the type expression I have written is actually
> perfectly meaningful.

I'm somewhat confused as to why this is different from simply
declaring a new opaque type:

type empty

Since there is no way to construct a value of the type, nor any way to
deconstruct such a value, how is it different?

John.