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. ^_^
