Sean Bolak thinks this is interesting: For example, the Array and Hash classes both define methods named empty? From 1. Introduction from The Ruby Programming Language by David Flanagan, Yukihiro Matsumoto Publisher: O'Reilly Media, Inc. Released: January 2008 Note Hash and Array both have an empty? method. Share this highlight http://www.safaribooksonline.com/a/the-ruby-programming/54505/ Twitter Facebook Google Plus Email Get Instant Access Now Start a Free Trial Have an account? Sign in. Minimise Unlock the rest of The Ruby Programming Language and 30,000 other books and videos By clicking this box, you confirm that you have read and agree to the terms and conditions of our Membership Agreement, and you understand that when your trial period ends, you will be required to provide billing information if you wish to continue using the service. Unlock the rest of this book Start a Free 10-Day Trial loading Learn about Safari for Business Have an account? Sign in.