Exercises from "7 languages in 7 weeks".

gistfile1.clj

;; Macros

(defmacro unless-else
  [cond if-true if-false]
  (list 'if cond if-false if-true))

(macroexpand '(unless-else false (println "false") (println "true")))
;;=> (if false (println "true") (println "false"))

(unless-else false (println "false") (println "true"))
;; false

;; Protocols

(defprotocol Enumerable
  (each [e f]))

(defrecord Array [elements]
  Enumerable
  (each [_ f]
        (map #(do (f %) %) elements)))

(def array (Array. [1 2 3]))

(each array #(println % "+ 1 =" (inc %)))
;; 1 + 1 = 2
;; 2 + 1 = 3
;; 3 + 1 = 4
;;=> (1 2 3)