Segregate mutation from logic

Segregate IO from logic

Eliminate procedures from logic.

The third axiom is sort of for free as it falls out automatically when someone enforces the first two. That’s basically imperative shell/functional core design philosophy which is basically identical to the rules of pure functional programming.

https://medium.com/ssense-tech/a-look-at-the-functional-core...

With fp you can think of these rules enforced as a language. Outside of fp we call it functional core / imperative shell and these rules can be enforced in an imperative language as a core design philosophy.