inline Functions — Zero-Cost Lambdas

// Without `inline` — every call allocates a Function object for the lambda
fun runIfTrue(condition: Boolean, action: () -> Unit) {
    if (condition) action()
}

// With `inline` — the lambda body is inlined at the call site
inline fun runIfTrueFast(condition: Boolean, action: () -> Unit) {
    if (condition) action()
}

// Non-local return: only legal in inline lambdas
fun findUser(users: List<String>): String? {
    users.forEach { name ->          // forEach is inline in stdlib
        if (name.startsWith("a")) return name    // returns from findUser!
    }
    return null
}

// `crossinline` if you can\'t allow non-local return
inline fun delayed(crossinline action: () -> Unit) {
    Thread { action() }.start()      // can't `return` out of action here
}

fun main() {
    runIfTrueFast(true) { println("hello") }
    println(findUser(listOf("bob", "alice", "carol")))   // alice
}