Advice functions in Emacs (defadvice, around, add-do-it)

advice_emacs_function.md

Around means that the advice is executed instead of the function. You can still call the original with ad-do-it.

Just to add a small example:

(defun foo (x)
  (* 2 x))

(defadvice foo (around bar activate)
  (setq ad-return-value
        (if (= x 1)
            42
          (+ 1 ad-do-it))))

(foo 1)
;; 42
(foo 2)
;; 5
(foo 3)
;; 7