I had thos professor, decades ago. He was a brilliant mathematician, and was so nerdy that he was able to actually explain complex mathematical concepts to the dumbest (me) of all his students. I don’t use the word genius very often, but this guy, in my opinion was exactly that. He was the guy that would tell you on day one: Everything I say in this class may be a test question. Of course, many just chuckled at that announcement, I probably did as well, but his words were prescient as his exams, all hand written and duplicated on a mimeograph machine, consisted of no more than 3 questions/problems. He had to grade on a curve because no one ever received 100% , yes that’s how tough his classes were.