Clojure functions need default parameters

So, I have decided to learn the clojure programming language and realized that this was a good place to document the things I learn.

The first thing I found out was that clojure doesn't support default parameters out of the box. So, as step one in learning clojure, I built a new defn that supports default parameters called defo and threw it up on GitHub. It came in useful as I am working my way though the 99 Lisp Problems

Now, instead of writing:

(defn foo
  ([x] (foo x 1))
  ([x y] (foo x y y))
  ([x y z] (+ x y z)))

I can now write:

(defo foo [x (y 1) (z y)] (+ x y z)

Optional parameters are embedded in parenthesis, with the name being followed by what the default value will be.

Apparently recur calls don't roll their args into the final & argument so this causes an error:

(defn go-to-zero [& col]
  (let [f (first col)])
  (if (= 0 f)
    (println "done")
    (recur (dec f))))
(go-to-zero 3)

So there is a part of the macro that would re-write the recur call, placing the final parameters into a list so it doesn't throw errors.