public Coordinate3D operator -( 
   Coordinate3D a,
   Coordinate3D b
)

{
  // Easy 3D vectors
  Coordinate3D v = new Coordinate3D(0, 1, 0);
  // v.Magnitude = 1

  Coordinate3D other = new Coordinate3D(-1, 0, 0);
  // other.Magnitude = -1

  double dotProduct = v.DotProduct(other);      // dotProduct = 0

  Coordinate3D crossProduct = v.CrossProduct(other);
  // crossProduct.X = 0
  // crossProduct.Y = 0
  // crossProduct.Z = 1

  Coordinate3D addVector = v.AddCoordinate3D(other);
  // addVector.X = -1
  // addVector.Y = 1
  // addVector.Z = 0

  // Rotate around x-axis
  Coordinate3D w = v;
  w.Rotate(Math.PI, other);
  // w.X = 0
  // w.Y = -1
  // w.Z = 0

  w.Scale(0.5);
  // w.X = 0
  // w.Y = -0.5
  // w.Z = 0

  w.Scale(-4);
  // w.X = 0
  // ww.Y = 2
  // w.Z = 0
  // w.Magnitude = 2

  w.Move(3, 2, 0);
  // w.X = 3
  // w.Y = 4
  // w.Z = 0
  // w.Magnitude = 5


  Coordinate3D emptyVector = new Coordinate3D();
  // emptyVector = (0, 0, 0)
  emptyVector.SetEmpty();
  // emptyVector = (Nan, Nan, Nan)

  Coordinate3D c1 = new Coordinate3D(2, 3, 4);
  Coordinate3D c2 = new Coordinate3D(9, -1, 3);

  var result_add = c1 + c2;
  // result_add = (11, 2, 7)
  var result_sub = c1 - c2;
  // result_sub = (-7, 4, 1)

  var b = result_sub != result_add;
  // b = true

  result_add = emptyVector + c1;
  // result_add = (Nan, Nan, Nan)

  b = result_add == emptyVector;
  // b = true
}