"A nice side effect (hmm) of immutability is you end up with pure functions." No, immutability doesn't magically give you purity. E.g. Rust gives you immutabil

"A nice side effect (hmm) of immutability is you end up with pure functions." No, immutability doesn't magically give you purity. E.g. Rust gives you immutability by default, yet you don't need anything to be mutable to get IO.