等分点打断非闭合曲线(错在哪里)

namezg

;等分点打断非闭合曲线法一
(defun c:dividebreak1 ()
(vl-load-com)
(command "_undo" "be")
(if (null num) (setq num 2))
(setq setnum (getint (strcat "\n请指定要等分点打断的段数<" (rtos num) ">：")))
(if setnum (setq num setnum))
(princ "\n请选择要等分点打断的非闭合曲线：")
(setq ss (ssget))  ;(ssget '((0 . "CIRCLE,ELLIPSE,*LINE,ARC")))
(setq n 0)
(if ss
  (repeat (sslength ss)
   (setq ssn (ssname ss n))
   (setq curve (vlax-ename->vla-object ssn))
   (if (vlax-curve-isClosed curve)
    (princ "\n所选对象为封闭对象，程序无法处理。")
    (progn
     (setq len (vlax-curve-getdistatparam curve (vlax-curve-getendparam curve)))
     (setq dlen (/ len num))  
     (repeat (- num 1)
      (setq pt (vlax-curve-getPointAtDist curve dlen))
      (command "break" ssn pt "@")
      (setq ssn (entlast))
      (setq curve (vlax-ename->vla-object ssn))
     )
    )
   )
   (setq n (1+ n))
  )
)
(command "_undo" "e")
(princ)
)
;等分点打断非闭合曲线法二
(defun c:dividebreak2 ()
(vl-load-com)
(command "_undo" "be")
(if (null num) (setq num 2))
(setq setnum (getint (strcat "\n请指定要等分点打断的段数<" (rtos num) ">：")))
(if setnum (setq num setnum))
(princ "\n请选择要等分点打断的非闭合曲线：")
(setq ss (ssget))  ;(ssget '((0 . "CIRCLE,ELLIPSE,*LINE,ARC")))
(setq n 0)
(if ss
  (repeat (sslength ss)
   (setq ssn (ssname ss n))
   (setq curve (vlax-ename->vla-object ssn))
   (if (vlax-curve-isClosed curve)
    (princ "\n所选对象为封闭对象，程序无法处理。")
    (progn
     (setq len (vlax-curve-getdistatparam curve (vlax-curve-getendparam curve)))
     (setq dlen (/ len num))
     (setq ss1 (ssget "x"))
     (command "divide" ssn num)  ;不加这行多段线会不准确，不知为什么？
     (setq ss2 (ssget "x"))
     (vl-cmdf "select" ss2 "r" ss1 "")
     (setq ssp (ssget "P"))     
     (repeat (- num 1)
      (setq pt (vlax-curve-getPointAtDist curve dlen))
      (command "break" ssn pt "@")
      (setq ssn (entlast))
      (setq curve (vlax-ename->vla-object ssn))
     )
     (command "_erase" ssp "")
    )
   )
   (setq n (1+ n))
  )
)
(command "_undo" "e")
(princ)
)
;为什么法一打断多段线时有时结果不正确，而法二却正确呢。怪事，哪位高手知道是什么回事。加不加(command "divide" ssn num)这行代码能起到什么作用呢，为什么不加就不正确了呢。