Ai Deng thinks this is interesting: Option[A] From Chapter 11. Monads from Functional Programming in Scala by Paul Chiusano and Rúnar Bjarnason Publisher: Manning Publications Released: September 2014 Note should be Option[B] here Share this highlight http://www.safaribooksonline.com/a/functional-programming-in/896527/ Twitter Facebook Google Plus Email Get Instant Access Now Start a Free Trial Learn about Safari for Business Have an account? Sign in. Minimise Unlock the rest of Functional Programming in Scala 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.