(beginning-of-defun, end-of-defun):

(beginning-of-defun, end-of-defun):
Push mark on the first call of successive command calls.
(insert-pair): New fun created from `insert-parentheses' with
`open' and `close' arguments added.  Enclose active regions
in paired characters.  Compare adjacent characters syntax with
inserted characters syntax before inserting a space.
(insert-parentheses): Call `insert-pair' with ?\( ?\).