Recursion is a mathematical concept. It is so rarely used in professional software engineering that I consider it a code smell and take a very close look at it

Recursion is a mathematical concept. It is so rarely used in professional software engineering that I consider it a code smell and take a very close look at it if I see it. If your prof is trying to teach you software engineering, he or she is right to ask you to choose the simplest way to express something. If your prof was teaching you about a recursive data structure, you would be considering the tradeoffs of a recursive implementation versus another one.