Dan Grossman of the University of Washington delivered a Programming Languages course on Coursera. Thanks to his lecture [1], I'll never forget "Function subty

Dan Grossman of the University of Washington delivered a Programming Languages course on Coursera. Thanks to his lecture [1], I'll never forget "Function subtyping is contravariant in its argument types and covariant in its return type" - even though I have to think to remember whether the subtype is the contravariant or covariant, I remember the principle very very clearly due to his antics. [1] https://www.youtube.com/watch?v=pb_k8h6RuAY https://www.youtube.com/watch?v=pb_k8h6RuAY