编写函数double rect-area(double length,double width=0),编写函数double rect-area(double length,double width=0)：当width=0时计算正方形面积,否则计算长方形面积

编写函数double rect-area(double length,double width=0),编写函数double rect-area(double length,double width=0)：当width=0时计算正方形面积,否则计算长方形面积
编写函数double rect-area(double length,double width=0),
编写函数double rect-area(double length,double width=0)：当width=0时计算正方形面积,否则计算长方形面积

编写函数double rect-area(double length,double width=0),编写函数double rect-area(double length,double width=0)：当width=0时计算正方形面积,否则计算长方形面积
double rect_area(double length,double width=0){
if(width==0.0) width=length;
return length*width;
}