[Kotlin]Kotlin OOP(3)-演算子過負荷、委任

data class Complex(val real: Double, val img: Double) {
    operator fun plus(other: Complex): Complex
        = Complex(real + other.real, img + other.img)
    override fun toString(): String = "$real+${img}i"
}

operator fun Complex.minus(other: Complex): Complex
    = Complex(real - other.real, img - other.img)

fun main() {
    val c1 = Complex(1.0, 1.0)
    val c2 = Complex(2.0, 2.0)
    val c3 = c1 + c2
    println(c3) // 3.0 + 3.0i
    println(c3 == Complex(3.0, 3.0)) // true
}

interface Base {
    fun print()
    fun printHello()
}

class BaseImpl(val x: Int) : Base {
    override fun print() { print(x) }
    override fun printHello() { println("Hello")}
}

class Derived(val b: Base) : Base by b {
    override fun print() {
        b.print()
        println("ok")
    }
}

// fun main() { // kts에서 작성
val b = BaseImpl(10)
val d = Derived(b)
d.print() // 10ok
d.printHello() // Hello // Derived 에서 구현하지 않았으나 b의 것을 사용
// }