JaDenis

func luhnCheck(number: String) -> Bool {
    var sum = 0
    let digitStrings = reverse(number).map { String($0) }
    
    for tuple in enumerate(digitStrings) {
        if let digit = tuple.element.toInt() {
            let odd = tuple.index % 2 == 1
            
            switch (odd, digit) {
            case (true, 9):