On Dec 15, 2004, at 8:30 AM, Simon Peyton-Jones wrote:
OK, I understand this.
1. You really do have overlapping instances, exactly as reported in
the error message.
2. The instance in Data.Graph.Inductive.Graph looks like this
instance ... => Eq (gr a b)
This is, as you say, crazy, because it overlaps with every
arity-2 type constructor.
In particular, it overlaps with Eq (a,b)
I'm copying Martin Erwig, who is, I think the maintainer of the
fgl/ package, because
it seems to me that it should be fixed.
I will probably have some time in January 2005 to work on this and a
couple of other
issues in the FGL.
--
Martin
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