Get outermost list from the current point

Question

From the point current position inside an Emacs buffer, how can I get the outermost list/s-expression which contains that point ?
Follows a few examples in order to illustrate what I want to achieve:

Example 1:

(defun xpto(arg)
  (+ 2 4)[point])

Output 1:

(defun xpto(arg)
      (+ 2 4))

Example 2:

(defun [point]xpto(arg)
  (+ 2 4))

Output 2:

(defun xpto(arg)
      (+ 2 4))

Example 3:

(defun xpto(arg)
  (+ 2 4))[point]

Output 3:

NIL

Is there any "off the shelf" function provided by Emacs that accomplishes the above mentioned behavior?
If not, can you guide me towards the easier approach in order to accomplish it ?

UPDATE #1

As suggested I tried the following approach:

;; Gets the outermost brackets based on point position
(defun get-outermost-brackets()
  (interactive)
  (car (last (nth 9 (syntax-ppss)))))


;; Assigns that function to a key
(global-set-key [(control p)] 'get-outermost-brackets)

However, after pressing CTRL+P I get no output no matter where the point is at.
What am I doing wrong ?

Answer 1

What you are looking for is the function parse-partial-sexp which returns the parser state (a 10-element list!) which you can use to figure out the start and end positions of your sexp.

Anther useful function will be scan-sexps.

UPDATE#1:

Your function get-outermost-brackets returns the position of of the outermost open paren, not a useful part of your buffer, and that value is not going to show in the echo area anyway.

UPDATE#2:

This will send the enclosing sexp to the echo area and the *Messages* buffer:

(defun get-enclosing-sexp (&optional pos)
  (interactive)
  (message "%s" (save-excursion
                  (goto-char (car (last (nth 9 (syntax-ppss)))))
                  (read (current-buffer)))))

Drop message if you want to return the sexp from the function instead of just showing it.

Where is my million?

Answer 2

(car (last (nth 9 (syntax-ppss)))) will give you the position of the outermost open paren (or nil if you're not within parentheses). If you want to get the corresponding expression as an s-exp, you can go to that position and then use read to get it.