How to solve an everyday problem with pure functional programming (stackoverflow.com)

Title is linkbait. The linked question isn't about the merits of functional programming. It's about a user trying to wrap their head around it.

I don't understand what I am supposed to take away from this link. I basically agree with the top-rated answer; that approach looks to be about how I'd do it. Is there something unusual here?

EDIT: This comment was written at a time when the submission had a less descriptive title.