class Cusip {
    function : native : IsCusip(s : String) ~ Bool {
        if(s->Size() <> 9) {
            return false;
        };

        sum := 0;
        for(i := 0; i < 7; i+=1;) {
            c := s->Get(i);

            v : Int;
            if (c >= '0' & c <= '9') {
                v := c - 48;
            } else if (c >= 'A' & c <= 'Z') {
                v := c - 55;  # lower case letters apparently invalid
            } else if (c = '*') {
                v := 36;
            } else if (c = '@') {
                v := 37;
            } else if (c = '#') {
                v := 38;
            } else {
                return false;
            };

            # check if odd as using 0-based indexing
            if(i % 2 = 1) {
                v *= 2;
            };

            sum += v / 10 + v % 10;
        };

        return s->Get(8) - 48 = (10 - (sum % 10)) % 10;
    }

    function : Main(args : String[]) ~ Nil {
        candidates := [
            "037833100",
            "17275R102",
            "38259P508",
            "594918104",
            "68389X106",
            "68389X105"
        ];

        each(i : candidates) {
            candidate := candidates[i];
            "{$candidate} => "->Print();
            if(IsCusip(candidate)) {
                "correct"->PrintLine();
            }
            else {
                "incorrect"->PrintLine();
            };
        };
    }
}