class Vector(d: Iterable[Double]) {
  def vector = d

  private def op(that: Vector, op: (Double, Double) => Double) =
    new Vector((vector, that.vector).zipped map op)
  private def un(op: Double => Double) = new Vector(vector map op)

  def this(ds: Double*) = this(ds toList)

  def +(that: Vector) = op(that, _ + _)
  def -(that: Vector) = op(that, _ - _)

  def +(trans: Double) = un(_ + trans)
  def -(trans: Double) = un(_ - trans)
  def *(x: Double) = un(_ * x)
  def /(x: Double) = un(_ / x)

  def unary_- = un(- _)

  def norm = sqrt(vector map (x => x*x) sum)
  def length = vector size
  override def toString = vector mkString("\n")
}