using System;
using IteratorsAndComparators;
using System.Collections.Generic;

namespace IteratorsAndComparators
{
    class Program
    {
        static void Main(string[] args)
        {
            var bookOne = new Book("Animal Farm", 2003, "George Orwell");
            var bookTwo = new Book("The Documents in the Case", 2002, "Dorothy Sayers", "Robert Eustance");
            var bookThree = new Book("The Documents in the Case", 1930);

            var libraryOne = new library();
            var libraryTwo = new library(bookOne, bookTwo, bookThree);
        }
    }

public class Book
    {
        public Book(string title, int year, params string[] authors)
        {
            this.Title = title;
            this.Year = year;
            this.Authors = authors;
        }

        public string Title { get; set; }

        public int Year { get; set; }

        public IReadOnlyList<string> Authors { get; set; }

    }

public class library : IEnumerable<Book>
    {
        private List<Book> books;

        public library(params Book[] books)
        {
            this.books = new List<Book>(books);
        }

        public IEnumerator<Book> GetEnumerator()
        {
            for (int i = 0; i < books.Count; i++)
            {
                yield return books[i];
            }
        }

        IEnumerator IEnumerable.GetEnumerator() => this.GetEnumerator();
    }
}