Programming Clojure, 3rd Edition

Living Without Multimethods

The best way to appreciate multimethods is to spend a few minutes living without them, so let’s do that. Clojure can already print anything with print/println. But pretend for a moment that these functions don’t exist and that you need to build a generic print mechanism. To get started, create a my-print function that can print a string to the standard output stream *out*:

src/examples/life_without_multi.clj

(defn my-print [ob]
  (.write *out* ob))

Next, create a my-println that calls my-print and then adds a line feed:

src/examples/life_without_multi.clj

(defn my-println [ob]
  (my-print ob)
  (.write *out* "\n"))

The line feed makes my-println’s output easier to read when testing at the REPL. For the rest ...