Looks like Rockit, the OO pr generator for Ruby, is abandoned.
It doesn't work with its own examples:
leikindpc324:~/rockit-0-3-8/examples/calculator$ ruby calculator.rb
`generate_pr': undefined local variable or method
`rockit_grammars_pr' for P:Module (NameError)
from calculator.rb:36:in `calculator_pr'
And some others have had similar troubles:
Anyone worked with Rockit recently?