Emacs Lisp如何在任意位置返回？

问题

我们知道Emacs Lisp并不像其他语言那样有return语句。那么，如果我想在程序的任意位置返回，那该如何做呢？

使用catch机制

有一种方法是，采用catch机制，下面是一个例子：

(defun lebe-fun-exit-any-arbitrary-point ()
  "Example show how to exit from a function at any arbitrary point in elisp."
  (interactive)
  (let ((a "a"))
    (catch 'return
      (when (equal "a" a)
        (throw 'return "non-local exit value"))
      (message "normal exit value"))))

执行下看：

ELISP> (lebe-fun-exit-any-arbitrary-point)
"non-local exit value"

参考： http://stackoverflow.com/questions/16248620/how-to-exit-from-a-function-at-any-arbitrary-point-in-elisp