It's worth noting that the reason behind pure functional programming is that ideally lets you reason about your business concerns without needing to worry so mu

It's worth noting that the reason behind pure functional programming is that ideally lets you reason about your business concerns without needing to worry so much about these things. The expectation is that pure functional languages gain a lot of benefits from (for instance) referential transparency which allow for optimizations which can not be provided by the compiler in languages which don't provide the same benefits to developers. It's also true that this is potentially just theoretical. Sure, there's no way to ensure these optimizations exist given your compiler's implementation, but the article actually does mention that this has other issues and it's only for demonstrative purposes. So, chances are it's a non-issue and if it is an issue then you still have the power to solve the problem later. No need for premature optimization, right?