Strange error in show for datatype

Ross Paterson ross@soi.city.ac.uk
Thu, 4 Oct 2001 14:29:43 +0100


On Thu, Oct 04, 2001 at 09:23:10AM +0000, Marcin 'Qrczak' Kowalczyk wrote:
> Thu, 4 Oct 2001 00:36:55 -0700, Simon Peyton-Jones <simonpj@microsoft.com> pisze:
> > Void was a type with one element.  What we really want here is
> > a type with no elements.  It's also useful to be able to introduce
> > such empty types for phantom-type purposes, so GHC now lets you say
> > 
> > 	data T
> > 
> > and get a type T with no values.
> 
> I think both Void and T have bottom, and both have no other values.

So this extension adds something we already have in Haskell 98, with either

	newtype Void = Void Void
or	data Void = Void !Void

(as I think Patrik Jansson pointed out)