;多边形区域面积计算
;入口参数：ddb多边形区域顶点坐标表((x1&nbspy1)&nbsp(x2&nbspy2)&nbsp(x3&nbspy3)&nbsp……&nbsp(xn&nbspyn))
(defun&nbspdbxmj(ddb)
&nbsp&nbsp&nbsp&nbsp(apply&nbsp'command&nbsp(append&nbsp(list&nbsp"pline")&nbsp(append&nbspddb&nbsp(list&nbsp"c"))))
&nbsp&nbsp&nbsp&nbsp(command&nbsp"area"&nbsp"o"&nbsp&nbsp(entlast)&nbsp&nbsp"erase"&nbsp(entlast)&nbsp""&nbsp"redraw")
&nbsp&nbsp&nbsp&nbsp(getvar&nbsp"area")&nbsp
)

;在不产生图元实体的情况下，使用下面函数
;入口参数：ddb多边形区域顶点坐标表((x1&nbspy1)&nbsp(x2&nbspy2)&nbsp(x3&nbspy3)&nbsp……&nbsp(xn&nbspyn))
(defun&nbspdbxmj(ddb)
&nbsp&nbsp&nbsp&nbsp(apply&nbsp'command&nbsp(cons&nbsp"_area"&nbsp(append&nbspddb&nbsp(list&nbsp""))))
&nbsp&nbsp&nbsp&nbsp(getvar&nbsp"area")&nbsp
)