A sealed trait controlling a class hierarchy

#!ek9
defines module site.structure.shapes

  defines trait

    ShapeLimit allow only Ellipse, Circle, Rectangle, Square, Triangle
      printDrawing()
        -> message as String
        //method body
        stdout <- Stdout()
        stdout.println(message)

  defines class

    Shape with trait of ShapeLimit as abstract
      draw() as abstract

    Ellipse extends Shape as open
      override draw()
        printDrawing("Ellipse")

    Circle extends Ellipse
      override draw()
        printDrawing("Circle")

    Rectangle extends Shape
      override draw()
        printDrawing("Rectangle")

    Triangle extends Shape
      override draw()
        printDrawing("Triangle")

    Square extends Shape
      override draw()
        printDrawing("Square")

  defines program

    DrawShapes()
      for shape in [Ellipse(), Circle(), Rectangle(), Square(), Triangle()]
        shape.draw()

Ellipse
Circle
Rectangle
Square
Triangle