foo.cpp: In constructor 'Vector2D::Vector2D(int, double, double)':
foo.cpp:18:6: warning: 'Vector2D::index' will be initialized after [-Wreorder]
  int index;
      ^
foo.cpp:17:9: warning:   'double Vector2D::x' [-Wreorder]
  double x, y;
         ^
foo.cpp:15:2: warning:   when initialized here [-Wreorder]
  Vector2D(int _idx, double _x, double _y): index(_idx), x(_x), y(_y){}
  ^
foo.cpp: In function 'int main()':
foo.cpp:67:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < vec.size(); i++)
                               ^
foo.cpp:69:51: error: 'printf' was not declared in this scope
   printf("%.3f %.3f\n", vec[i].x+eps, vec[i].y+eps);
                                                   ^
foo.cpp:39:6: warning: unused variable 'm' [-Wunused-variable]
  int m = b - a + 2;
      ^