A polyglot's guide to multiple dispatch

Links to parts 2, 3 and 4:

Python: https://eli.thegreenplace.net/2016/a-polyglots-guide-to-mult...

Common Lisp: https://eli.thegreenplace.net/2016/a-polyglots-guide-to-mult...

Clojure: https://eli.thegreenplace.net/2016/a-polyglots-guide-to-mult...