Comment by mitt_romney_12

This is an interesting approach but it has some issues with more more advanced effects. For example if you have a function that uses mutable state you would need to have the state both as an input and an output (for the original and the updated state) `update_mut: State -> String -> State` this isn't very economical as is probably worse than just `update_mut: String -> State ()`. If you commit to just having the parameters act as "markers" that don't actually relate to the implementation then you can get away with `update_mut: State -> String -> ()` but then you use one of the big benefits of effect systems which is that you can change the way effects work and have multiple different implementations.