You hit the nail on the head with regarding to pure functional style. What I usually find useful it to use OO at high level, macro level, structural level to o

You hit the nail on the head with regarding to pure functional style. What I usually find useful it to use OO at high level, macro level, structural level to organize the code, and to use functional style at the lower level to build reusable functions. The lower level basic pure functions form the building blocks that can be reused in different circumstances since they are stateless. The domain specific and state specific aspects are left to OO to abstract and organize.