World -> (World, Char) is one possible type for getChar. There was an approach called Fudgets [1], based on stream processing, and in this case the signature wo

World -> (World, Char) is one possible type for getChar. There was an approach called Fudgets [1], based on stream processing, and in this case the signature would be getChar :: SP Response Char. Stream processing type used in Fudgets also admits monadic interface implementation. [1] https://research.chalmers.se/en/publication/1015 https://research.chalmers.se/en/publication/1015