Although every care has been taken to ensure the accuracy of the content of this book, mistakes do happen. If you find a mistake in the book - maybe a mistake in the text or in the code - the author would be grateful if you would report this. By doing so, you can save other readers from frustration and help to improve subsequent versions of this book. Please report errata by writing to, entering "errata" as the subject line, and the details of the errata as the message. Once your errata are verified, your submission will be accepted and the errata added to the list.