Extension-Functions.kt

data class Item(val name: String, val price: Float)                                   // 1  

data class Order(val items: Collection<Item>)  

fun Order.maxPricedItemValue(): Float = this.items.maxBy { it.price }?.price ?: 0F    // 2  
fun Order.maxPricedItemName() = this.items.maxBy { it.price }?.name ?: "NO_PRODUCTS"

val Order.commaDelimitedItemNames                                             // 3
    get() = items.map { it.name }

fun main() {

    val order = Order(listOf(Item("Bread", 25.0F), Item("Wine", 29.0F), Item("Water", 12.0F)))
    
    println("Max priced item name: ${order.maxPricedItemName()}")                     // 4
    println("Max priced item value: ${order.maxPricedItemValue()}")
    println("Items: ${order.commaDelimitedItemNames}")                                // 5

}