Earlier quoted context omitted.
> My experience is that functional alone is impossible, since the only useful thing a program can do is through state changes Some programs are simply pure functions. If your program entry point accepts a string and returns a string, then you can write useful things, such as compilers, image processing, grep, etc, entirely as pure functions.
Unless you want logging with timestamps.
You can't counter that with an example of a program that you can't write as a pure function.