This can also be a classic case of why coding interviews are often a poor approximation of real world tasks. Imperative (and especially dynamic) languages typi

This can also be a classic case of why coding interviews are often a poor approximation of real world tasks. Imperative (and especially dynamic) languages typically make it easy to get something "working", but it can take many iterations or lots of unit tests until it's robust enough to be worthy of handling a production load. That time spent futzing around with it isn't often capturable in an interview. If it is, chances are the interview isn't asking something representative of real-world scenarios, or it's taking a very narrow slice of one where someone's approach is going to change a lot of they're not just working in the narrow slice. Functional (and especially typed functional) languages do make it harder to get something up and running, but they tend to have a nice side effect that if the compiler is satisfied, it won't need more work. That usually happens because you can capture the domain in a type declaration that the compiler requires you to account for all cases of. And if you're missing something, it's easy to adjust because the act of adding another case to your domain makes your compiler point out exactly where else to update your code.