instance inference

Ross Paterson ross at
Mon Feb 6 07:21:56 EST 2006

On Mon, Feb 06, 2006 at 12:07:54PM +0000, Ross Paterson wrote:
> On Mon, Feb 06, 2006 at 11:53:17AM -0000, Simon Peyton-Jones wrote:
> > Your (1-Ross) ensures that every variable in the assertion does occur in
> > the head.  But I'm not sure that the size-reduction argument is
> > watertight in the presence of fundeps.  (E.g. in example 15 it *looks*
> > as if the size goes down, but it doesn't.) 
> Hmm, "improvement".  But this is a problem for the GHC rules too, isn't
> it?

Sorry, wrong example (I was thinking of example 6).  Example 15 would
be ruled out, as the proposed rules ignore functional dependencies.
I think this is a bug in GHC, and have already filed it as #681.

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