Dear Hakellions PS: In my message about uses of GADTs I asked | ... | d) send Omega code, which GHC won't understand, but which | demonstrates some cunning use of GADTs | All of these would be useful, even (c) and (d) --- we can eyeball the code. I should have also asked you to send examples of Chameleon code. http://www.comp.nus.edu.sg/~sulzmann/chameleon/ that uses GADTs. (Actually Chameleon does a lot more besides GADTs. For example, it has an interesting type debugger.) Simon