View Compilation Error

0_0_17425040_31571.cpp:56:42: error: could not convert 'Point{0.0, 0.0, false, false}' from 'Point' to 'Point&'
 int inter(Line a,Line b,Point &rp=Point()){//0：不相交 1：相交 2、3：端点相交，a在b某一边 4：重合
                                          ^