public Parser currencySignIs() {
        if (currencySignIsParser == null) {
           FutureParser future = scoped("currencySignIs");
           currencySignIsParser = future;
           future.setParser(
               sequence(
                   token("CURRENCY"),
                   optional(
                       token("SIGN")
                   ),
                   optional(
                       token("IS")
                   ),
                   literal()
               )
           );
        }

        return currencySignIsParser;
    }