defer.kt

import java.lang.Exception

fun main() {
    runrunrun {
        defer { println("HI") }
        defer { println("HI") }
        defer { println("HI") }

        println("HELLO")
        println("HELLO")
        println("HELLO")

        throw Exception("HI")
    }
}

fun runrunrun(block: DeferBag.() -> Unit) {
    val bag = DeferBag()
    try {
        bag.block()
    } finally {
        bag.runAll()
    }
}

class DeferBag {
    private val list: MutableList<() -> Unit> = mutableListOf()

    fun defer(block: () -> Unit) {
        list.add(block)
    }

    fun runAll() {
        for (val element in list) {
            element()
        }
    }
}