func swapValues<T>(_ a: inout T, _ b: inout T) {
    let temporary = a
    a = b
    b = temporary
}

var first = 10
var second = 42
swapValues(&first, &second)
print(first, second) // 42 10

var nameOne = "Alice"
var nameTwo = "Bob"
swapValues(&nameOne, &nameTwo)
print(nameOne, nameTwo) // Bob Alice