はじめてのClojure勉強会#5 unlessを実装

unless.clj

(defmacro unless
  "testを評価し、testがtrueの場合はthenを評価した値を返す。そのほかの場合はelseを評価した値を返す"
  ([test then & forms]
   (let [[else & r] forms]
     (if (empty? r)
       `(if (not ~test) ~then ~else)
        (throw (RuntimeException. "Too many arguments to unless."))))))


(unless true (println "Hello World"))
(unless false (println "Hello World2"))
(unless true (println "hoge1") (println "fuga1")) 
(unless false (println "hoge1") (println "fuga2")) 
(unless false (println "foo") (println "bar") (println "buzz"))