tp4.scala

// Won't compile
trait Shape {
  //       vvv (hmm)
  def area(???): Double
}

case class Circle(radius: Double)
case class Rectangle(width: Double, length: Double)

class CircleShape extends Shape {
  override def area(circle: Circle) : Double = math.Pi * math.pow(circle.radius, 2)
}

class RectangleShape extends Shape {
  override def area(rectangle: Rectangle): Double = rectangle.width * rectangle.length
}

//                                            vvv (but what about this?)
def areaOf(shape: Shape): Double = shape.area(???)