说明：  在CAD实现闭合PL线和闭合简单直线的面积直接计算,非常适合才CAD的竣工测量里面实用,通常情况下,CAD只能计算PL线围成的面积,而该程序解决了简单直线的自动闭合判断和面积计算
(CAD to achieve closure in the PL line and closed simple direct calculation of the size of a straight line, very suitable for measuring only the completion of CAD utility which is usually the case, CAD can only be calculated PL line surrounded the area, and the procedures for the settlement of a simple straight-line automatic closure and the area to determine)