I've always been uneasy with FP-style coding for three reasons:

   - you have strictly no idea how your code will be evaluated by the CPU. Some people love that aspect. It makes me immensely queasy. I might be a control freak.

   - as much as I love the idea an cleanliness of composing functions, having to abandon mutability for that is way too hefty a price to pay. There are situations where overwriting memory is the darndest best way to do things. Yes, side-effects are hard to code with, but just like gotos, there are situations where they are the best solution.

   - I've always felt that FP coders are way too focused the beauty of their code rather that the industrial strength of it, which includes: readability, how easy it is to change, efficiency. Proper production code shouldn't be origami puzzles.