That's a point worth emphasizing. Functional programming is advocated as a means of simplifying programming. When you program with pure functions which always r

That's a point worth emphasizing. Functional programming is advocated as a means of simplifying programming. When you program with pure functions which always return the same results for the same arguments, things become like mathematics, expressions can be simplified and reasoned about. Yes. But I don't see how such a purely mathematical viewpoint could fit nicely into the real-time world where processes evolve concurrently and can take different times to do things on different executions. In the real world things are mutable, and concurrent programming must take that into account. Therefore it is "complicated".