foo.cpp: In function 'void makeline(Circle, Circle)':
foo.cpp:40:31: warning: unused variable 'upyy' [-Wunused-variable]
      upxy = sdis * x.r / dis, upyy = sdis * y.r / dis, b = upxy - k * (x.x + upxx);
                               ^
foo.cpp: In function 'int main()':
foo.cpp:70:10: error: 'M_PI' was not declared in this scope
  s = tan(M_PI / 2.0 - x);
          ^