class Vektor2D (val x: Double, val y: Double) {  
   def +(v: Vektor2D) = new Vektor2D(x + v.x, y + v.y)  // Vektoraddition
   def -(v: Vektor2D) = new Vektor2D(x - v.x, y - v.y)  // Vektorsubtraktion
   def unary_- = new Vektor2D(-x, -y)  // Unärer Minusoperator
   def *(a: Double) = new Vektor2D(a*x, a*y)
   override def toString = "(" + x + ", " + y +")"
}

class WrappedDouble(val a: Double) {
   def *(v: Vektor2D): Vektor2D = v*a
}

object VektorMain extends Application {
   implicit def wrapDouble(a: Double) = new WrappedDouble(a)
   val v = new Vektor2D(1, 2);  val w = new Vektor2D(-1, 1) 
   println(-v +","+ (v + w) +","+ (v - w) +","+ 2*v) // (-1,-2),(0,3),(2,1),(2,4)
}