Functional Swift: Pure functions in swift

import Foundation

func add(_ x: Int, _ y: Int) -> Int {
    return x + y
}

func square(_ x: Int) -> Int {
    return x * x
}

func raiseToPowerofThree(_ x: Int) -> Int {
    return x * x * x 
}  

print(add(1, 2))
print(add(3, 4))
print(square(2))
print(square(6))
print(raiseToPowerofThree(2))