Swift make method parameter mutable?

Question

How can I deal with this error without creating additional variable?

func reduceToZero(x:Int) -> Int {
    while (x != 0) {
        x = x-1            //         


        

Answer 1

Solution using Swift5 with Functional Programming...

func reduceToZeroFP(x:Int) -> Int {
    x == 0 ? x : reduceToZeroFP(x: x - 1)
}