abstract class GeoObject {
  def symbolize: String
}

class Point extends GeoObject {
  def symbolize: String = "."
}

class Circle(r: Double) extends GeoObject {
  def symbolize: String = "O"
  def area: Double = r * r * 3.14
}

val p = new Point
val c = new Circle(2.0)

p.symbolize
c.symbolize
c.area