On Thu, Jul 01, 2010 at 12:29:57AM +0200, Claus Reinke wrote:
> As I said, even if you just want to drop 'Error', you could define
> 'fail s = Left (error s)'. That would still be less defined than the
> current instance, but more defined than the proposed instance.

That didn't occur to me -- it seems harmless enough, but it wouldn't be
enough to support pattern binding with the Either monad, would it?