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The latest version of the book is P3.1, released about 1 month ago. If you've bought a PDF of the book and would like to update it to this version (for free), visit your home page.

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  • Typo
  • Tech. error
  • Suggestion
  • Maybe next edition
  • Not a problem
  • Reported in: P3.1 (28-Apr-20)
PDF page: 35
The example regarding private method calls no longer works on ruby 2.7. Looks like it's caused by Ruby issue number 16783 (which I would link to, but ...more...
Paolo Perrotta says: Thank you, Szymon. Yes, I'm aware that the behaviour of private methods changed slightly in Ruby 2.7. That's one of the few corner cases where information in the book became stale. However, it's not worth for us going through indexing/typesetting again to fix those rare inaccuracies. If anything, we should wait for Ruby 3, and then consider a third edition. I'll leave this erratum here in case we ever decide for that. Thank you for reporting this!