Question

How to use higher-order functions in Kotlin

Answer 1

// A higher‑order function is a function that does at least one of the following:
// 1. Takes another function as an argument
// 2. Returns a function as its result
// If it does either one, it qualifies.

// Higher-order function: takes a function as an argument
fun applyTwice(fn: (Int) -> Int, x: Int): Int {
    return fn(fn(x))
}

// A simple function to pass in
fun add3(n: Int): Int {
    return n + 3
}

fun main() {
    // Use the higher-order function
    val result = applyTwice(::add3, 5) // 5 + 3 = 8 + 3 = 11

    println(result)
}


/*
run:

11

*/

 

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Answer 2

// A higher‑order function is a function that does at least one of the following:
// 1. Takes another function as an argument
// 2. Returns a function as its result
// If it does either one, it qualifies.

// makeMultiplier is a higher‑order function because it RETURNS another function
fun makeMultiplier(n: Int): (Int) -> Int {

    // This inner function forms a closure and remembers the value of n
    return { x: Int ->
        x * n // Uses the captured value n
    }
}

fun main() {
    // double_val is now a function created by makeMultiplier(2)
    // It remembers n = 2 through closure
    val double_val = makeMultiplier(2)

    // Calling double_val(10) multiplies 10 by the captured n (which is 2)
    println(double_val(10))
}



/*
run:

20

*/

 

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