Best entry video Functional Programming in 40 Minutes • Russ Olsen • GOTO 2018 You can find the slide here. Mindset We don’t need to put our knowledge aside when learning functional programming. It’s more of a refactoring. Functions in mathmatics It’s just maps from set to set. Functions donn’t compute somthing in math. It just is. A thing. Once the function was defined, the input-output correspondence never changes by other factors, which means, there is no side effects.