class Book {
private:
    string isbn;
    string author;
    string title;
    string year;
    string publisher;
    string page_count;
    //friend auto BookList::search_by_author(string);
public:
    Book(string _isbn, string _author, string _title, string _year, string _publisher, string _page_count) {
        isbn = _isbn;
        author = _author;
        title = _title;
        year = _year;
        publisher = _publisher;
        page_count = _page_count;
    }
    auto serialize() {
        auto s = isbn + "^^^" + author + "^^^" + title + "^^^" + year + "^^^" + publisher + "^^^" + page_count;
        return s;
    }
};

class BookList {
private:
    vector<Book> list;
public:
    auto add(string isbn, string author, string title, string year, string publisher, string page_count) {
        list.emplace_back(isbn, author, title, year, publisher, page_count);
        return;
    }
    auto search_by_author(string author) {
        vector<Book> matches;
        for (auto book : list)
            /*if (book.author == author)
                matches.push_back(book);*/
        return matches;
    }
    auto serialize(vector<Book> entries) {
        vector<string> serialized;
        for (auto entry : entries)
            serialized.push_back(entry.serialize());
        return serialized;
    }
} books;