Elisp with examples

(defun foo (num)
  (message "the number is %d" num))

(defun testadvice (fn num)
  (let ((num (+ num 1)))
    (funcall fn num)))

(advice-add 'foo :around 'testadvice)
(advice-remove 'foo 'testadvice)

(setq x 1)
(defmacro inc (var)
        (list 'setq var (list '1+ var)))

(defmacro ++ (var)
  (list 'setq var (list '1+ inc x)

(inc x)
(++ x)

(defun myfun (aa bb &optional cc dd)
  "test optional arguments"
  (insert aa bb cc dd)
  )
;; call it
(myfun "1" "2" "3" "4")

(myfun "myaa" "mybb" nil "mydd")

(defun ff (aa bb &rest cc)
  "test rest arguments"
  (message "%s" cc) ; cc is a list
  )

;; test
(ff "1" "2" "3" "4")
;; ("3" "4")