Functional programming easily cost me hundreds of hours without much to show for it. Monad transformers, free monads, final tagless... this rabbit hole is very very deep.
No regrets though, would suffer through this again!
I haven't done any serious functional programming but I think the point is that overall it saves you time. It might take longer to write the program but you get fewer bugs, reliable caching and so on.
I know that with Rust the time-to-robustness is much lower than with Python for example.
Functional programming easily cost me hundreds of hours without much to show for it. Monad transformers, free monads, final tagless... this rabbit hole is very very deep.
No regrets though, would suffer through this again!