elisp - concat of parts of list

Question

What am I missing?

As they say: In every program is a bug.

(defun test-test ()
    (interactive)
    (let ((lll (list "a" "b")))
        (message (concat "<" (car lll) ":" (cdar lll) ">"))
))

Error:

concat: Wrong type argument: listp, "a"

Answer 1

你拼错了你的cadr:)。

(defun test-test ()
  (let ((lll (list "a" "b")))
    (message (concat "<" (car lll) ":" (cadr lll) ">"))))

另外，如果您不打算用它来调用它，则不需要交互式M-x

Answer 2

在菜单中启用“Options => Enter Debugger on Error”，您将获得一个可以澄清问题的回溯。