On Fri, 2004-12-17 at 09:38, John Prevost wrote:
> 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 = [ ]

> 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?

Polymorphic variants are extensible and algebraic .. 
an abstract type is neither.

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