class Point[T <: Number](val x:T, val y:T) {

  def + (other : Point[T]) : Point[T]  = new Point[T] ( x + other.x, y + other.y)

  def - (other : Point[T]) : Point[T] = new Point[T] ( this.x - other.x, this.y - other.y)
  def unary_ : Point[T] = new Point[T](-this.x, -this.y)
  def == (other : Point[T]) : Boolean = (this.x == other.x && this.y == other.y)
  def != (other : Point[T]) : Boolean = !(this == other)
}