The other thing about functional programming is it involves a sort of tradeoff that's very different from object orientation. It makes functions into "first cla

The other thing about functional programming is it involves a sort of tradeoff that's very different from object orientation. It makes functions into "first class (language) objects". Manipulating functions directly is a very power ability. As tradeoff, making functions pure and making variable immutable limits that power and makes your operations on functions understandable as well as powerful. Because if you take functions with side effects and manipulate these in various ways, you can quickly wind-up with a powerful but incomprehensible system. This means that "functional effects" do sometimes do best as something like subsystems called by the main system.