View Compilation Error

0_0_14972705_2643.cpp: In member function 'sqr& sqr::operator+(sqr&)':
0_0_14972705_2643.cpp:14:34: error: invalid initialization of non-const reference of type 'sqr&' from an rvalue of type 'sqr'
   if(x1==0||an.x1==0) return sqr(); 
                                  ^
0_0_14972705_2643.cpp:16:70: error: invalid initialization of non-const reference of type 'sqr&' from an rvalue of type 'sqr'
    return sqr(max(x1,an.x1),max(y1,an.y1),min(x2,an.x2),min(y2,an.y2));
                                                                      ^
0_0_14972705_2643.cpp:17:19: error: invalid initialization of non-const reference of type 'sqr&' from an rvalue of type 'sqr'
   else return sqr();
                   ^