For some context, conal did the pioneering work on "classic" Functional Reactive Programming with Hudak, before the Haskell language had moved to monadic IO. O

For some context, conal did the pioneering work on "classic" Functional Reactive Programming with Hudak, before the Haskell language had moved to monadic IO. Originally, IO in Haskell was done based on streams as in Miranda from which it was inspired. A program is then a transformation on a stream of operating system events into a stream of operating system commands, both represented as data. That's pretty cool, because it makes it easy to write your program and then mock the operating system rather than actually touching the real world. The closest we have to this now is the "interact" function, which allows you to model your IO as a transformation of a stdin stream to a stdout stream. Conal isn't much convinced that monadic IO was the best solution to the IO problem. The idea that monadic IO is a "pure" or "denotational" way to interact with the real world is arguably pretty weak, and that's the point of conal's post here: if you take the idea to its logical conclusion, we might end up just concluding that cpp is pure and denotational. Instead, conal has worked on FRP approaches to interacting with the real world which are pure and have a very denotational feel to them: you're just writing down functions from time and a time-stamped stream of events. I still hold out enormous hope for this approach, but I'm not placing any bets on it.