/in/foo.cc: In function 'Point rotate(Point, Point, double)':
/in/foo.cc:16:82: error: invalid operands of types 'double' and 'double' to binary 'operator%'
     const double d = distance(a, b), t = angle + atan((a.y - b.y) / (a.x - b.x)) % (2 * PI);
                                                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~