Well while I can produce large swaths of elegant code when I need crazy instances I usually call upon my colleague for his invaluable assistance. I don't claim to be an expert in the language. Many people know much more about it than me.
I've been trying to come up with a general way to rank Haskell experience, and so far I've got:
Beginner: Can read the basic syntax, knows about E.G. Monads and folds
Intermediate: Understands and can use the more advanced classes like Applicative, Arrow, lenses, and how to use things like fix
Advanced: ??? Makes new powerful classes/libraries like Pipe, Conduit, or Netwire? Can easily translate a problem domain into a concise and elegant type representation.
Maybe there needs to be some more layers in there, I don't know... also the advanced level feels weak to me. I'm still somewhere between beginner and intermediate myself.
Well I don't claim to understand the mathematical basis of Monads, and I don't use arrows and just started using applicative more often. Lenses rock and I have used those for a long time. I do build my own Monad Transformers so maybe I am still a beginning with intermediate tendencies. :-)
