visitor.kt

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)
    )

    fun area(shape: Shape) = when (shape) {
        is Square -> shape.side * shape.side
        is Circle -> shape.radius * shape.radius * Math.PI
        is Rectangle -> shape.height * shape.width
    }
    val totalArea = shapes.sumByDouble { area(it) }
    println("Total area: $totalArea")

    fun perimeter(shape: Shape) = when (shape) {
        is Square -> 4 * shape.side
        is Circle -> 2 * Math.PI * shape.radius
        is Rectangle -> 2 * shape.height + 2 * shape.width
    }
    val totalPerimeter = shapes.sumByDouble { perimeter(it) }
    println("Total perimeter: $totalPerimeter")
}