Elisp: Apply Function (List to Args)

Sometimes you have a list, you want to feed them as arguments to a function.

There are 2 ways to do that:

• Use the function apply, e.g. (apply 'f (list 2 3 4))
• Use the Backquote Reader Macro

apply

(apply FUNCTION &rest args_or_list)

Call FUNCTION with args_or_list.

If the last argument in args_or_list is a list, it is flattened out and feed as args to the function.

;; test function
(defun ff (x y z)
  "return args as one string"
  (format "%s %s %s" x y z))

;; normal usage
(ff 2 3 4)
;; "2 3 4"

;; HHHH------------------------------

;; use apply, to turn a list into args
(apply 'ff (list 2 3 4))
;; "2 3 4"

;; HHHH------------------------------

;; multi arg example. the last arg, if list, is turned into args
(apply 'ff 2 (list 3 4))
;; "2 3 4"

funcall

(funcall FUNCTION &rest args)

Call FUNCTION with args.

💡 TIP: this is useful when the function name is a variable, value known only at run-time.

;; test function
(defun ff (x y z)
  "return args as one string"
  (format "%s %s %s" x y z))

;; normal usage
(ff 2 3 4)
;; "2 3 4"

;; use funcall
(funcall 'ff 2 3 4)
;; "2 3 4"