My rulebooks aren't what you're thinking, I think. They're only a more bureaucratic kind of 'extend. I tend to store extensible operators as mutable collections of extensions, which mostly comes in handy so I can store a reference to a rulebook somewhere (like in a variable in a namespace) before all the extensions have been introduced, and it'll automatically reflect those later extensions. I can also sort rulebooks to establish precedence or peek into rulebooks to troubleshoot individual rules without leaving the REPL.
Whether you would actually use such a macro in practice, I don't know, but it was relevant to my point that you can use a macro to make extending less verbose.
My apologies for using the term "rulebooks", I couldn't recall the name of the macro you were describing.
Oh, I implemented 'def-extension-type in lathe.js as lathe.deftype().
// Define a constructor _.Seq and a rulebook _.iffirstRb.
lathe.deftype( _, "Seq", "iffirstRb" );
// Define a constructor _.Seq using an existing rulebook.
lathe.deftype( _, "Seq", _.iffirstRb );
This is not to be confused with the 'deftype I was talking about in that thread. >.>
I use it in exactly two places so far, and the rest of the time I've been cheating by defining types in a more traditional OO JavaScript way. But I'm totally interested in figuring out things like this that could help. I think Traits.js is a pretty interesting option for this, and I'm not against message-passing at this point either. ^_^
