It's fundamentally necessary, since I/O is stateful. Functional languages have language-specific ways of doing this, but you can see examples of this in non-fun

It's fundamentally necessary, since I/O is stateful. Functional languages have language-specific ways of doing this, but you can see examples of this in non-functional languages. https://www.destroyallsoftware.com/talks/boundaries https://www.destroyallsoftware.com/talks/boundaries is a great, practical talk about this.