[Haskell] seeking papers with good examples of the use of GADTs

[Norman Ramsey]

I have a class of beginning functional programmers; we're approaching
end of term, and I'd like them to learn about GADTs.  One of my goals
in the class is to give students practice learning by reading papers,
so I am asking for recommendations of papers that have good examples
of GADTs in action.   Papers I've used in the past have included

  Pottier and Gauthier 2005: Polymorphic Typed Defunctionalization and
  Concretization, in Higher-Order and Symbolic Computation

  Pottier and Régis-Gianas 2006: Towards Efficient, Typed LR Parsers,
  in Electr. Notes Theor. Comput. Sci

and

  Peyton Jones et al. 2006: Simple unification-based type inference
  for GADTs, in the 11th ACM SIGPLAN International Conference on
  Functional Programming.

Unfortunately the first two rely on concepts in which my students have
little background (LR parsing and defunctionalization respectively),
and the the third, while it opens with a nice example, is primarily
about the (now obsolete) type-inference algorithm, rather than about
how to use GADTs.

I am hoping some of you may have suggestions about other papers that
would be good tutorials in the use of GADTs.


Norman