Is Giles saying that with the help of Rubinius you can do Lisp-style code generation in Ruby? I don't know much about Rubinius but this doesn't sound right. Lisp macros let you manipulate the program's AST in compile time very easily because the AST is made of sexp's, just like the program code itself. This is due to the peculiar Lisp syntax. Lisp code generation seems quite different from the monkey patching techniques demonstrated in the presentation. Am I missing something?
I didn't take that to be his main point, but yes, I think so. Though I think it would be more accurate to say "Lisp lets you manipulate the program's AST trivially because the AST is the code".
This is basically Greenspun's 10th Law again. There's no magic in Lisp that's computationally impossible in another language, but it might be simpler to just write a Lisp in that language first. Rubinius did something even tougher: they wrote a Ruby. The advantage of this is that it's backwards-compatible with all their existing code, while upgrading to sexps would not be.
I think the monkeypatching corresponds to only the front half of Lisp macros. The macroexpand part comes from making the monkeypatches log Ruby code, and then running the log.
