멀티 Trim, Extend Lisp 사용 절차를 알고 싶어요.

(defun C:LK (/ ob1 pt1 roof roof1 ssn obl1 sp ep la ang pt2 pt3 anp anp2
dist1 dist2)
(setvar “cmdecho” 0)
(COMMAND “UCS” “S” “1” “Y”)
(COMMAND “UCS” “”)
(setq ob1 (ssget)
pt1 (getpoint “nSelect to Extend or Trim point: “)
roof (sslength ob1)
roof1 0
);
(repeat roof
(setq ssn (ssname ob1 roof1)
obl1 (entget ssn)
sp (assoc 10 obl1)
ep (assoc 11 obl1)
la (assoc 8 obl1)
ang (rtd (angle (cdr sp) (cdr ep)))
pt2 (polar pt1 (dtr (+ ang 90)) 500)
pt3 (inters (cdr sp) (cdr ep) pt1 pt2 nil)
anp (cons 11 (list (car pt3) (cadr pt3)))
anp2 (cons 10 (list (car pt3) (cadr pt3)))
dist1 (distance (cdr sp) pt3)
dist2 (distance (cdr ep) pt3)
)
(cond ((> dist1 dist2)
(setq obl1 (subst anp ep obl1))
)
((> dist2 dist1)
(setq obl1 (subst anp2 sp obl1))
)
)
(entmod obl1)
(setq roof1 (1+ roof1))
)
(print)
(COMMAND “UCS” “R” “1”)
):defun
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주석과 함께 사용 절차좀 알려주세요!!!