record Question { prompt: string, answer: i64 }
fn is_correct(question: Question, answer: i64) -> bool {
    return answer matches question::answer;
}
fn summary(label: string, correct: i64, answered: i64, total: i64) -> unit {
    print(label + ". Correct: " + format_i64(correct) + "; answered: " + format_i64(answered) + "; total: " + format_i64(total) + ".\n");
}
fn start_main() -> i64 {
    let questions: list<Question> = [
        Question { prompt: "2 + 3?", answer: 5 },
        Question { prompt: "9 - 4?", answer: 5 },
        Question { prompt: "3 * 4?", answer: 12 },
        Question { prompt: "12 / 3?", answer: 4 },
        Question { prompt: "7 + 8?", answer: 15 }
    ];
    let total: i64 = length(questions);
    var index: i64 = 0;
    var answered: i64 = 0;
    var correct: i64 = 0;
    print("Local quiz: " + format_i64(total) + " questions. Type q to stop.\n");
    while (index < total) {
        let question: Question = questions[index];
        print("Question " + format_i64(index + 1) + "/" + format_i64(total) + ": " + question::prompt + " ");
        let line: string = read_line();
        if (line matches "q") {
            summary("Stopped early", correct, answered, total);
            return 0;
        }
        let parsed: result<i64> = parse_i64(line);
        if (parsed::ok) {
            if (is_correct(question, parsed::value)) {
                print("Correct.\n");
                correct = correct + 1;
            } else {
                print("Wrong. Expected " + format_i64(question::answer) + ".\n");
            }
            answered = answered + 1;
            index = index + 1;
        } else {
            print("Retry: " + parsed::error::code + ". Use ASCII digits, for example 5, or q.\n");
        }
    }
    summary("Completed", correct, answered, total);
    return 0;
}