Example using defnk to take optional params

defnk.clj

(ns defnk-example
  (:use [clojure.contrib.def :only (defnk)]))

(defnk some-fn
  [x y :opt1 :a :opt2 :b]
  (str "x: " x " opt1: " opt1 " opt2: " opt2))

defnk-example> (some-fn "x" "y" :opt1 5 :opt2 10)
"x: x opt1: 5 opt2: 10"
defnk-example> (some-fn "x" "y")
"x: x opt1: 0 opt2: 1"
defnk-example> (apply some-fn "x" "y" [:opt1 :b])
"x: x opt1: :b opt2: :b"