Sun Oct 23 09:27:48 EDT 2011

Overlapping Instances

When using type classes to represent compile-time recursive data
structures, one often runs into "Overlapping instances" errors.

While overlapping instances in data structure pattern matching are not
an issue (order is important!), for type classes it is a problem.  I
don't exactly understand why, but it seems it's possible to avoid
this.  I had to use the following extension in my case.  What does it