> [1] Yes, Conal Elliots arguments are very relevant here. > A function with minimal side-effects Clarification, what I mean with “minimizing the use of side

> [1] Yes, Conal Elliots arguments are very relevant here. > A function with minimal side-effects Clarification, what I mean with “minimizing the use of side effects” is not about within a function, but in a program. Exaggerated example: You could write Haskell in a style where everything returns an IO and mutates some global state. Not doing that, and having most things pure is useful due to the simplified reasoning in the pure parts. > There's two important steps that you've rolled into one. Have I? What I want to say is that I do believe the syntactic distinction between calling side-effecting functions vs pure functions is useful. Do I need to care about how the compiler enforces that? Does the specific encoding need to be part of the language semantics? Do I need to be able to model it monadically within the language? > This is where you get your nice functional properties meaning that your compiler won't let you mix them up. I may have formulated this a bit flippantly, but I think you mean the same here as I did when I said that “marked with an ! so they are easier to spot” I did have in mind that this is checked by the compiler. And I think we also agree that this separation is a good thing.