I stopped reading it after it said concurrency in Ruby was "N/A". That's a silly statement for a language that has threads and coroutines built in, as well as a number of event loop and actor libraries.<p>When run on JRuby, threads also offer parallelism.<p><a href="http://ruby-doc.org/core-2.2.0/Thread.html" rel="nofollow">http://ruby-doc.org/core-2.2.0/Thread.html</a><p><a href="http://ruby-doc.org/core-2.2.0/Fiber.html" rel="nofollow">http://ruby-doc.org/core-2.2.0/Fiber.html</a>