Experience reports using indexed monads in production?

Question

In a previous question I discovered the existence of Conor McBride\'s Kleisli arrows of Outrageous Fortune while looking for ways of encoding Idris examples in Haskell. My effor

Answer 1

Another nice example is mutexes with lock-unlock check at compile time. You can find this example on Stephen Diehl website:

http://dev.stephendiehl.com/hask/#indexed-monads