poly.clj

(ns polymorphism.core)

(def basket
  [{:price 88 :name "Chocolate"}
   {:price 22 :name "Newspaper"}
   {:price 3  :name "Lettuce"} ])

(defn receipt [items]
  (map
    #(str (:price %) " " (:name %))
    items))

(defmulti tax (fn [item] (:kind item)))

(defmethod tax :food [item] (-> item :price (* 1.2)))
(defmethod tax :alcohol [item] (-> item :price (* 1.4)))
(defmethod tax :default [item] (-> item :price (* 1.3)))

(defn receipt-multi [items]
  (map
    #(str (tax %) " " (:name %))
    items))

(defprotocol Taxable
  (taxed [item]))

(defrecord food [name] Taxable (taxed [item] (-> item :price (* 1.2))))

(defn receipt-protocol)