This seems interesting. Maybe I can use something similar next year to generate some interest. Without IO (which is monads, which is too advances since we also do functional C# and functional java paradigms in the same course) the subject matter is always a bit dry since the students have nothing but the ghci repl to get any interaction or feedback going.
? This would give them a little more liveliness but wouldn't require them to understand anything beyond "IO () is something that the repl can run". If they're feeling exploratory, maybe give them a few monadic combinators like >> to play around with, possibly specialized to IO.
You could also build a "sandbox" monad specifically for the class/framework. Let the students treat the monad as a blackbox Turing machine/state machine, unless they get time/interest/show aptitude to dive deeper. Doing that gives you the benefit that they don't accidentally google "Haskell IO" and fall down the monad rabbit hole without some preparation.
