elisp insert below/above [arg]th line like vim command "o" and "O" (but different)

gistfile1.txt

(defun add-new-line-below(&optional arg)
  "adds new line [arg]th below current line.
This command is compatible with relative-linum.el."
  (interactive "p")
  (if (not (numberp arg))
      (setq arg 1))
  (next-line (- arg 1))
  (move-end-of-line 1)
  (newline-and-indent))
  
(defun add-new-line-above(&optional arg)
  "adds new line [arg]th above current line.
You have to 
This command is compatible with relative-linum.el.
You have to pay attention to the difference between c-add-new-line-below and this. If you execute this simply, you give this function argument '1' genetally。And please (setq line-move-visual nil)"
  (interactive "p")
  (setq arg (or arg 0))
  (if (not (numberp arg))
      (setq arg 0))
    (previous-line arg)
  (back-to-indentation)
  (split-line))