darjeeling - a roundabout route

Well by now if you follow Ruby much you've probably noticed the whole Will Rubinius be an acceptable Lisp ponderings or brainstormings or whatever you want to call it. And if you know me at all, you'd be aware that the union of such concepts is exactly the kind of thing that would excite me.

So I meddled around a bit with ParseTree. Honestly, it's ridiculous; the Ruby side of this kind of thing has been made more or less trivial by Ryan's great work:

require 'rubygems'
require 'parse_tree'

class Infuser
  def self.brew(klass)
    lisp(ParseTree.new.parse_tree(klass)).sub(/\(\(/,  '(class Object (')
  end

  def self.lisp(leaf)
    leaf.respond_to?(: map) ? "(#{leaf.map{|l| lisp(l)}.join(' ')})" :  leaf
  end
end

Would you look at that. Like I said; pretty trivial. While we're on the subject of trivial, consider this:

class Foo
  def bar
    1 + 1
  end
end

Infuser.brew Foo gives us this:

(class Object
       (class Foo (const Object) 
	      (defn bar 
		(scope
		 (block (args) 
		   (call (lit 1) + (array (lit 1))))))))

At this point you may be tempted to think yourself, "Hey, that looks like lisp! Run it through the compiler and see what it does." Unfortunately Ruby's object model is wildly divergent from Common Lisp's. (Though you could say that's very fortunate depending on your opinion of CLOS—I won't go there.) The point is, running the above code would require getting a subset of Ruby's object model running in Common Lisp. Running nontrivial code would basically require getting it completely ported.

Now that sounds hugely daunting task. It probably is. But I've got this wild idea that you'd only have to actually implement a fairly small subset of this in CL itself. The rest could be translated over from Ruby. I'm thinking all the portions of the implementation currently written in C would need to be redone in CL, and if the port is accurate enough then the portions of Ruby-the-implementation which are written in Ruby-the-language will be able to be translated through the infuser shown above. Now I know that the official Ruby has gobs and gobs of stuff implemented in C, but it seems to be a stated goal of Rubinius to decrease the C-to-Ruby ratio. That may be something that could be leveraged here. (Note to self: need to check out MetaRuby as well.)

There's another hiccup though—it seems there's no solid BDD framework for Common Lisp. A few weeks back I started writing behave.el for Emacs Lisp. The pieces are all coming together in my head, so it seems the thing to do at this point would be to finish it, port it to CL, and then start porting the Rubinius specs to it.

Update: this was not actually a good idea.

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