To my utter shock, it turns out that I am not perfect. There are mistakes in my books!
A couple of readers made me aware of a typo in Functional Programming in R. It is just a typo, but I can easily see why it can confuse readers.
Much much worse is an error in Functional Data-Structures in R. An entire section is utter rubbish. Please don’t read the section on dequeus. The errata has a correct implementation and this post has a much better explanation than the book.
If you find errors in my books, then please let me know so I can update the errata lists and fix them if there are more editions.