Function Defintion

[Artist]

Hi, How I can get the function definition via lisp code?
 Lambda expression may be ok.

I know how to see it via find-function and I don't want to use macro.

Something like
(get-definition 'mark-whole-buffer)

should return

(defun mark-whole-buffer ()
  "Put point at beginning and mark at end of buffer.
You probably should not use this function in Lisp programs;
it is usually a mistake for a Lisp function to use any subroutine
that uses or sets the mark."
  (interactive)
  (push-mark (point))
  (push-mark (point-max) nil t)
  (goto-char (point-min)))



Thanks You
[aritst]