[a-saleh]

Somewhere I heard that 80% pure 20% impure is a good sweet-spot. I think I read it somewhere on this blog: https://prog21.dadgum.com/56.html but it does kinda ring true.

What I experienced more, is that function to be state-less is more important than it to be pure. And many functional languages (i.e. erlang or clojure) don't really have a way to curb I/O, but they have strong primitives for dealing with mutable-state or they forbid-it altogether.