सर्वोत्तम अभ्यास

data class Point(val x: Int) {
    operator fun plus(o: Point) = Point(x + o.x)
}

fun main() {
    val a = Point(1)
    val b = a + Point(2)
    println("${a.x} ${b.x}")
}

class Cart {
    val items = mutableListOf<String>()
    operator fun plusAssign(item: String) { items.add(item) }
}

fun main() {
    val c = Cart()
    c += "book"
    println(c.items)
}

data class N(val v: Int) {
    operator fun plus(o: N) = N(v + o.v)
}

fun main() {
    println((N(1) + N(2) + N(3)).v)
}

data class Log(val lines: List<String>) {
    fun append(line: String) = Log(lines + line)
}

fun main() {
    println(Log(emptyList()).append("start").lines)
}

data class Id(val v: Int)

fun main() {
    val set = hashSetOf(Id(1), Id(1))
    println(set.size)
}

data class N(val v: Int) {
    operator fun plus(o: N) = N(v + o.v)
    operator fun times(o: N) = N(v * o.v)
}

fun main() {
    println((N(2) + N(3) * N(4)).v)
}

data class Range2(val start: Int, val end: Int) {
    // contains: is value inside the range?
    operator fun contains(v: Int) = v in start..end
}

fun main() {
    println(5 in Range2(1, 10))
}

class Team(val members: List<String>) {
    operator fun contains(name: String) = name in members
}

fun main() {
    val t = Team(listOf("Ann", "Bo"))
    println("Ann" in t)
}

data class Temperature(val c: Int) {
    fun warmerThan(o: Temperature) = c > o.c
}

fun main() {
    println(Temperature(30).warmerThan(Temperature(20)))
}

data class V(val x: Int) {
    operator fun plus(o: V) = V(x + o.x)
}

fun main() {
    println((V(2) + V(5)).x)
}