Mapbasic程序困难求解答

<P>Mapbasic下写的程序，检查没错误，但是运行时提示invalid window identifier:0   (无效的窗口标识符),不知道哪儿出错了！程序如下：</P>
<P>'产生射线<BR>include"Mapbasic.def"<BR>'open table"F:\毕业论文\毕业设计\图\射线层\射线1"<BR>'open table"F:\毕业论文\毕业设计\图\边界"<BR>dim i,n as integer<BR>dim r,x1,y1,x2,y2,x0,y0,x3,y3,b,a as float</P>
<P><BR>''''''''原点坐标、半径、射线条数、视区坐标<BR>x0=1048236.365<BR>y0=3986187.05<BR>r=18000<BR>n=108<BR>x1=1028084.308<BR>y1=3967218.86<BR>x2=1071914.501<BR>y2=4002503.15<BR>'''''''''''''''''''''''''''''''''''''''''''</P>
<P>Set CoordSys nonearth<BR>units "m"<BR>bounds(x1,y1) (x2,y2)</P>
<P>for i=0 to n-1<BR>b=i*360/n<BR>a=b*deg_2_rad<BR>x3=r*cos(a)<BR>y3=r*sin(a)<BR>     create line<BR>     (x0,y0) (x0+x3,y0+y3)<BR>next</P>

设置 地图窗口  可编辑图层  等

需要制定绘图的窗口ID<div><div>Dim WinID As Integer</div><div>Dim LayerNum As Integer</div><div><span class="Apple-tab-span" style="white-space:pre"> </span></div><div><span class="Apple-tab-span" style="white-space:pre"> </span>WinID = FrontWindow()</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>If WindowInfo(Winid,WIN_INFO_TYPE) <> WIN_MAPPER Then</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>Note "当前不是地图窗口！"</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>Exit Function</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>End If</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>LayerNum = MapperInfo(WinID,MAPPER_INFO_EDIT_LAYER)</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>If LayerNum <= 0 Then</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>Note "请先设置可编辑图层！"</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>Exit Sub</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>End If</div></div>

    create line  (x0,y0) (x0+x3,y0+y3)
这句有问题，line 后面或者要一个变量，或者要一个地图窗口。