monad transformer library

Lauri Alanko
Mon, 9 Jun 2003 11:52:32 +0300

On Fri, Jun 06, 2003 at 10:19:40AM +0100, Ross Paterson wrote:
> On Fri, Jun 06, 2003 at 09:14:18AM +0100, Simon Peyton-Jones wrote:
> > That is, deriving works for arbitrary classes for newtypes, just using
> > the instance
> > for the representation type.  This greatly alleviates the pain you refer
> > to.  It's documented in the GHC user manual.
> I recall that you came across a glitch with the specification of this
> feature -- is that all sorted out now?

There is of course the obvious glitch that "the instance for the
representation type" is _not_ used as is when deriving Read or Show. An
understandable special case, but still a bit ugly.

Lauri Alanko