adding runtime polymorphism

koans/about_runtime_polymorphism.clj

@@ -0,0 +1,35 @@
+(defn hello
+  ([] "Hello World!")
+  ([a] (str "Hello, you silly " a "."))
+  ([a & more] (str "Hello to this group: "
+                   (apply str
+                          (interpose ", " (concat (list a) more)))
+                   "!")))
+
+(defmulti diet (fn [x] (:eater x)))
+(defmethod diet :herbivore [a] __)
+(defmethod diet :carnivore [a] __)
+(defmethod diet :default [a] __)
+
+(meditations
+  "Some functions can be used in different ways - with no arguments"
+  (= __ (hello))
+
+  "With one argument"
+  (= __ (hello "world"))
+
+  "Or with many arguments"
+  (= __
+     (hello "Peter" "Paul" "Mary"))
+
+  "Multimethods allow more complex dispatching"
+  (= "Bambi eats veggies."
+     (diet {:species "deer" :name "Bambi" :age 1 :eater :herbivore}))
+
+  "Different methods are used depending on the dispatch function result"
+  (= "Simba eats animals."
+     (diet {:species "lion" :name "Simba" :age 1 :eater :carnivore}))
+
+  "You may use a default method when no others match"
+  (= "I don't know what Rich Hickey eats."
+     (diet {:name "Rich Hickey"})))

koans/path_to_enlightenment.clj

@@ -19,4 +19,5 @@
 (load "about_functions")
 (load "about_conditionals")
 (load "about_higher_order_functions")
+(load "about_runtime_polymorphism")
 (println "You have acheived clojure enlightenment. Namaste.")