Rubinius uses Ruby to implement Ruby.
Like JRuby, Rubinius is an alternative implementation of Ruby. Much of Rubinius’s internal source code is written in Ruby itself instead of in only C or Java. Rubinius implements built-in classes, such as
Integer, just as you would—with Ruby code!
This design offers a unique opportunity for you to learn about Ruby internals. If you aren’t sure how a particular Ruby feature or method works, you can read the Ruby code inside Rubinius to find out, without special knowledge of C or Java programming.
Rubinius also includes a sophisticated virtual machine ...