I would like to define this function:

(defun . (object method &rest args)
 (apply (plist-get object method) args))

But, not surprisingly I get: if: Dot in wrong context

Not surprising because it looks like a cons cell and isn't. I can use some other character like @ or function name like dot, but it seems like it should be possible to use . too. Is there any way to do something like that?

The application is for a closure that defines a plist of functions, and I want something like a dot notation to access them.

This does work, but the double dot is a little unconventional from what I am used to:

(setq c (let ((counter 0))
      (list :inc (lambda (&optional dx)
               "Increment counter by DX (default=1)."
               (incf counter (or dx 1))))))

(defun .. (object method &rest args)
  (apply (plist-get object method) args))

(.. c :inc)

2 Answers 2


Yes, you can.

(defun \. (&optional n)
  "This is Lisp function `.'.
It just invokes`forward-char`."
  (interactive "p")
  (forward-char n))

C-h f . tells you about it.

M-x . RET invokes it interactively.

(\. 42) and (\.) invoke it from Lisp.

As you can see, you need to escape the . (with a backslash) when using the function name in Lisp.

  • Enabler! Now we're going to have a "backslash-dot" library!
    – ebpa
    Apr 17, 2017 at 1:13
  • 1
    Hope not. It was already misguided (IMHO) to use just - as a library prefix. Too clever by half. ;-)
    – Drew
    Apr 17, 2017 at 1:15
  • This didn't work for me in emacs 25.1.1, I still get the wrong dot context error. Is there anything special needed to make it work? Apr 17, 2017 at 1:16
  • @JohnKitchin Works for me in 25.1.1. Have the backslash in both places (definition and invocation)?
    – ebpa
    Apr 17, 2017 at 1:20
  • Hm. it does work in a clean emacs... Thanks for confirming. Apr 17, 2017 at 1:22

The answer is: You can define a function named . but it does not help you much. The problem is not that you cannot define a function named . but that the evaluation of such a function is rather complicated.

 '(setq c (let ((counter 0))
        (list :inc (lambda (&optional dx)
             "Increment counter by DX (default=1)."
             (incf counter (or dx 1))))))

(fset (intern ".") (lambda (object method &rest args)
             (apply (plist-get object method) args)))

;;; Evaluation of the function named `.':
(funcall (intern ".") c :inc)

You cannot evaluate it as (. c :inc) because you get the "dot in wrong context"-error.

  • Interesting. It looks like the version below also works with this: (\. c :inc). I guess if it takes an escape to do it, then .. doesn't seem so bad! Apr 17, 2017 at 1:27

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.