小编Hen*_*ros的帖子

我正在编写一个宏来实现when内置宏,这里是代码:

(defmacro when-valid
  "Macro that does a series of actions if the condition
    is true"
  [condition & actions]
  `(if ~condition (~cons 'do ~actions) nil))

但当我评估它时:

(when-valid (< 1 2) (println "hello") (println "dear"))

我得到输出:

hello
dear
clojure-noob.core=> NullPointerException   
clojure-noob.core/eval17411

我应该nil而不是NullPointerException.有谁知道我做错了什么？

谢谢.