Runtime Polymorphism

ClojureScript Koans Runtime Polymorphism Answers
http://clojurescriptkoans.com/#runtime-polymorphism/1


(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)))


1)Some functions can be used in different ways - with no arguments

(=  "Hello World!"  (hello))

2)With one argument

(= "Hello, you silly world." (hello "world"))

3)Or with many arguments

(=  "Hello to this group: Peter, Paul, Mary!"  (hello "Peter" "Paul" "Mary"))


4)Multimethods allow more complex dispatching

(= "Bambi eats veggies." (diet {:species "deer", :name "Bambi", :age 1, :eater :herbivore}))

 (defmethod diet :herbivore [a] "Bambi eats veggies." )

5)Different methods are used depending on the dispatch function result

(= "Simba eats animals." (diet {:species "lion", :name "Simba", :age 1, :eater :carnivore}))

 (defmethod diet :carnivore [a] "Simba eats 
animals.")

6)You may use a default method when no others match

(= "I don't know what Rich Hickey eats." (diet {:name "Rich Hickey"}))

 (defmethod diet :default [a] "I don't know 
what Rich Hickey eats.")