higher-order functions

HigherOrder2.kt

fun main(args: Array<String>) {
    println(sum(1, 3))       // 4
}

fun sum(a: Int, b: Int) = higherOrderFunction2().let {
    it(a, b)
}

fun higherOrderFunction2(): (Int, Int) -> Int {
    return { a, b -> a + b }
}