pufface

class Square {
  type = "Square" as const
  constructor(public side: number) {}
}
class Circle {
  type = "Circle" as const
  constructor(public radius: number) {}
}
class Rectangle {
  type = "Rectangle" as const

pufface

class Shape {
  constructor() {
    this.type = this.constructor.name
  }
}
class Square extends Shape {
  constructor(side) {
    super()
    this.side = side
  }

pufface

interface Shape {
    fun area(): Double
    fun perimeter(): Double
}
class Square(val side: Double) : Shape {
    override fun area() = side * side
    override fun perimeter() = 4 * side
}
class Circle(val radius: Double) : Shape {
    override fun area() = radius * radius * Math.PI

pufface

sealed class Shape
class Square(val side: Double) : Shape()
class Circle(val radius: Double) : Shape()
class Rectangle(val width: Double, val height: Double) : Shape()

fun main() {
    val shapes = listOf(
        Square(5.0),
        Circle(4.0),
        Rectangle(6.0, 7.0)