Some results on a project I am working on were slightly skewed and this is why:

template <typename Point>
struct Vector
  double x, y;
  Vector() = default; // doubles initialize to 0
  Vector(Point& A, Point& B) : x(B.x - A.x), y(B.y - A.y) {}

  void normalize()
    x /= norm();
    y /= norm();

  double norm()
    return std::sqrt(x * x + y * y);


An hour of my life to debug it that I’m never getting back. I should have guessed earlier because results were skewed only by the y-axis.