Question

I would like to create a function that allows to:

(incf vara varb varc vard)

Instead of

(incf vara)
(incf varb)
(incf varc)
(incf vard)

What I do not understand is how to be able to send more arguments, how to define that in a function?

(defun inc (&rest arg)
(interactive)
(mapcar ‘incf arg)
)

This increases the argument, but ofcourse does not save them back into the variables.

How to go about this?

Answer 1

It should work:

(require 'cl)

(setq a 1)
(setq b 2)

(defun inc (&rest arg)
  (interactive)
  (mapc (lambda (x) (incf (symbol-value x))) arg))

(inc 'a 'b)

(message "%s %s" a b) => (2 3)

You have to quote each argument otherwise (inc a b) becomes (inc 1 2) before executing inc.