It seems like both can be used to define functions that you can implement later, with different data types. AFAIK the major difference is that defmulti works on maps and defprotocol works on record...

I am running Clojure 1.3.0 with La Clojure in IntelliJ IDEA while reading The Joy Of Clojure, and on section 4.1.3 (page 64), the authors demonstrate integer overflow with the following code: (+ I...