Clojure: Macro

gistfile1.clj

;; defmacro
;; only run at compile time

;; Simple
(defmacro unless [condition expression]
  (list 'if condition nil expression))

(unless (> 2 3) true)
;; (if (> 2 3) true nil)

;; Multiple Expressions
(defmacro unless
  ([condition expression]
    (list 'if condition nil expression))
  ([condition expression-1 expression-2]
    (list 'if condition expression-1 expression-2)))

(unless (> 2 3) true false)
;; (if (> 2 3) true false)