> having the ability to mutate is only a good thing there hard to discuss without specific examples, but it is provably bad thing whenever you share the value

> having the ability to mutate is only a good thing there hard to discuss without specific examples, but it is provably bad thing whenever you share the value that you're mutating. if your problem boils down to crunching numbers, maybe even in a couple threads without needing to communicate and cooperate between them - sure, mutability is hands down best approach, but in other 99.9999% of problems it is a hindrance.