https://itnext.io/pros-and-cons-of-functional-programming-32cdf527e1c2
https://www.quora.com/What-are-some-limitations-disadvantages-of-functional-programming-Where-does-it-break-down-when-you-want-to-get-things-done/answer/Tikhon-Jelvis
https://alvinalexander.com/scala/fp-book/disadvantages-of-functional-programming
https://stackoverflow.com/questions/44965/what-is-a-monad
https://stackoverflow.com/questions/2488646/why-are-side-effects-modeled-as-monads-in-haskell
http://www.cs.cornell.edu/courses/cs3110/2018fa/textbook/ads/monads.html
http://adit.io/posts/2013-04-17-functors,_applicatives,_and_monads_in_pictures.html