> is there a trade off with functional programming in regards to debugging? I have looked and large and hairy C++/Java/C#/Erlang/Python programs. I think overa

> is there a trade off with functional programming in regards to debugging? I have looked and large and hairy C++/Java/C#/Erlang/Python programs. I think overall Erlang are the easiest to debug. Two reasons are: state is most likely to be passed in explicitly, and data is immutable. Compare to, say, looking at a class instance in an OO language, which inherited from a bunch of other classes, and then had some methods called on it, modifying its internal state, and now you're and asking yourself "hmm, this seems broken, but how did we even get to this point?". vs looking at function like "update_state(State, NewData, ...) -> ... NewState.". In the second case it is clear what is happening, what the old state was, what the new is. If the bug happens on a live system, it is easy to attach a trace that would trigger only when NewData matches something or old state matches, or both match.