John Todd R.I.P.

John Todd was a wonderful mathematics teacher at Caltech. As undergrads, myself and a couple of friends asked him if we could enroll in one of his graduate classes. He said yes. We were worried that we might not be able to keep up with the grad students. It turned out the grad students were even more worried, that we might show them up. In any case, it all worked out fine. It was a memorable class that gave us a taste of what real mathematics research was like. John Todd was unusual in that he didn't have a PhD, just a Bachelor's degree, so you had to be careful to call him Professor Todd not Dr. Todd. He was a great teacher that I remember well to this day.