Drawing circles to all vertices of polyline

[Dayananda]

 (defun foo (p)
   (if (vl-consp p)
     (or (vl-member-if
           (function (lambda (a) (equal (list (car a) (cadr a)) (list (car p) (cadr p)))))
           plst
         )
         (setq plst (cons (cdr
                            (assoc 10
                                   (entmake (list '(0 . "CIRCLE") (cons 10 p) (cons 40 *COV:RAD*)))
                            )
                          )
                          pLst
                    )
         )
     )
   )
 )

This Mr Fixo's code. Please modify this to insert circles into midpoints of vertex.