请大家帮忙看下代码

晓晓晓晓

这是我在论坛首页看到的土方量程序，不是很懂，希望朋友们能给解释下，感谢，

2. ;;;获取多义线顶点
   
3. ;;;  Code:
   
4. (vl-load-com)
   
5. 
   
6. 
   
7. (defun c:nihe ()
   
8. ;;;提取拟合范围
   
9. 
   
10.     (setvar "cmdecho" 0)
    
11.     (setq osmode-save (getvar "OSMODE"))
    
12.     (setvar "OSMODE" 0)
    
13. 
    
14. ;;;    (setvar "bilpmode" 1)
    
15.     (setq f1 (getfiled "abc" "d:/" "txt" 1))
    
16.     (setq f1 (open f1 "w"))
    
17.     (setq ent (car (entsel "\n选取范围界线:")))
    
18.     (setq jd-lst nil) ;;建立格网与边界交点表2d
    
19.     (setq ptlst (get-ploy-vers ent))
    
20. ;;;取ptlst中xy极值的方法
    
21.     (setq xmax (apply 'max (mapcar 'car ptlst))
    
22. xmin (apply 'min (mapcar 'car ptlst))
    
23. ymax (apply 'max (mapcar 'cadr ptlst))
    
24. ymin (apply 'min (mapcar 'cadr ptlst))
    
25.     )
    
26.     (setq dx   (getreal "\n方格网边长:")
    
27. half-dx (/ dx 2.0)
    
28.     )
    
29.     (setq dy dx)
    
30.     (command "offset"
    
31.     dx
    
32.     ent
    
33.     (list (+ xmax 2) (+ ymax 3))
    
34.     ""
    
35.     )
    
36.     (setq ent2 (entlast))
    
37.     (setq ptlst2 (get-ploy-vers ent2))
    
38.     (entdel ent2)
    
39.     (setq lname (getstring "\n输入图层名:"))
    
40. 
    
41.     (setq ss0 (ssget "CP" ptlst2 (list (cons 8 lname))))
    
42.     (if ss0
    
43. (progn (setq slen (sslength ss0))
    
44.       (setq ss-lst nil)
    
45. )
    
46. (exit)
    
47.     )

;;;获取多义线顶点<br /> ;;;  Code:<br /> (vl-load-com)<br /> <br /> <br /> (defun c:nihe ()<br /> ;;;提取拟合范围<br /> <br />     (setvar "cmdecho" 0)<br />     (setq osmode-save (getvar "OSMODE"))<br />     (setvar "OSMODE" 0)<br /> <br /> ;;;    (setvar "bilpmode" 1)<br />     (setq f1 (getfiled "abc" "d:/" "txt" 1))<br />     (setq f1 (open f1 "w"))<br />     (setq ent (car (entsel "\n选取范围界线:")))<br />     (setq jd-lst nil) ;;建立格网与边界交点表2d<br />     (setq ptlst (get-ploy-vers ent))<br /> ;;;取ptlst中xy极值的方法<br />     (setq xmax (apply 'max (mapcar 'car ptlst))<br /> xmin (apply 'min (mapcar 'car ptlst))<br /> ymax (apply 'max (mapcar 'cadr ptlst))<br /> ymin (apply 'min (mapcar 'cadr ptlst))<br />     )<br />     (setq dx   (getreal "\n方格网边长:")<br /> half-dx (/ dx 2.0)<br />     )<br />     (setq dy dx)<br />     (command "offset"<br />     dx<br />     ent<br />     (list (+ xmax 2) (+ ymax 3))<br />     ""<br />     )<br />     (setq ent2 (entlast))<br />     (setq ptlst2 (get-ploy-vers ent2))<br />     (entdel ent2)<br />     (setq lname (getstring "\n输入图层名:"))<br /> <br />     (setq ss0 (ssget "CP" ptlst2 (list (cons 8 lname))))<br />     (if ss0<br /> (progn (setq slen (sslength ss0))<br />       (setq ss-lst nil)<br /> )<br /> (exit)<br />     )

(setq f1 (getfiled "abc" "d:/" "txt" 1))
(setq lname (getstring "\n输入图层名:"))希望能给解释下这2段的意思，谢谢了。