Swift return type is a function of function

//
//  main.swift
//  Ultimate
//
//  Created by Mewlan Musajan on 3/5/21.
//

import Foundation

func stepForward(_ input: Int) -> Int {
    return input + 1
}

func stepBackward(_ input: Int) -> Int {
    return input - 1
}

func chooseStepFunction(_ backward: Bool) -> (Int) -> Int {
    return backward ? stepBackward : stepForward
}

var currentValue = 3
let moveNearerToZero = chooseStepFunction(currentValue > 0)

print("Counting to zero:")
while currentValue != 0 {
    print("\(currentValue)...")
    currentValue = moveNearerToZero(currentValue)
}
print("zero!")