sealed class Animal {
    abstract val weight: Int
}

data class Dog(
    override val weight: Int,
    private val barkSound: String
) : Animal()

data class Cat(
    override val weight: Int,
    private val meowSound: String
) : Animal()


fun main() {
    val dog : Animal = Dog(weight = 1, barkSound = "woof")
    
    // what's the most elegant way to allow the following?
    val heavierDog = dog.copy(weight = weight + 1) 
}

sealed class Animal {
    abstract val weight: Int
    abstract fun copy(
        weight: Int = this.weight
    ): Animal
}

data class Dog(
    override val weight: Int,
    private val barkSound: String
) : Animal() {
    override fun copy(weight: Int): Animal {
        return copy(weight = weight, barkSound = this.barkSound)
    }
}

data class Cat(
    override val weight: Int,
    private val meowSound: String
) : Animal() {
    override fun copy(weight: Int): Animal {
        return copy(weight = weight, meowSound = this.meowSound)
    }
}


fun main() {
    val dog : Animal = Dog(weight = 1, barkSound = "woof")
    val heavierDog = dog.copy(weight = 2)
    println(heavierDog)
}

copy

hashcode

equals

component

copy