 
         func scanNumber() -> Token? {
 
-            let symbolSet = NSMutableCharacterSet.decimalDigitCharacterSet()
-            symbolSet.addCharactersInString(".-")
-
             var string: NSString?
 
-            if scanner.scanCharactersFromSet(symbolSet, intoString: &string) {
+            if scanner.scanCharactersFromSet(numberScanningSet, intoString: &string) {
 
                 if let string = string as? String {
 

        }

        func scanNull() -> Token? {
            if scanner.scanString("null", intoString: nil) {
                return .Null
            }


        func scanString() -> Token? {

            var string: NSString?

            if scanner.scanString("\"", intoString: nil) &&
                scanner.scanCharactersFromSet(stringScanningSet, intoString: &string) &&
                scanner.scanString("\"", intoString: nil) {

                    if let string = string as? String {
