Shape.kt

open class Shape{
    class Circle(val radius: Float) : Shape()
    class Rect(val base: Float, val height: Float) : Shape()
    
    fun area() : Float{
        return when(this){
            is Shape.Circle -> 2.0f * 3.14f * this.radius
            is Shape.Rect -> this.base * this.height 
            else -> 0.0f
        }
    }
}

fun main()=print(Shape.Circle(2.0f).area())