>> Enter TurboEditor. Because of this one simple little thing (not so little actually) that my friend found, we were able to decompile the entire CanDo program and figure out how it worked. Remember that important thing? Yes, that’s right, CanDo is actually written in itself and it could actually modify pieces that are currently executing. Let me clarify this just a little. One card could modify another card, then pull that card into focus. The actual card wasn’t currently executing, but the deck was. In fact, we came to find that CanDo was merely a facade. We also found that there was a very powerful object oriented, fully reentrant, self-modifying, programming language under that facade of a UI. In fact, this is how CanDo’s UI worked. Internally, it could take an element, decompile it, modify it and then recompile it right away and make it go live, immediately adding the updated functionality to a button or slider.

While CanDo could modify itself, it never did this. Instead, it utilized a parent-child relationship. It always created a child sandbox for user-created decks. This sandbox area is where the user built new CanDo Decks. Using this sandbox approach, this is how CanDo built and displayed a preview of your deck’s window. The sandbox would then be saved to a deck file and then executed as necessary.

"While it could modify itself, it never did this" - an underappreciated constraint of the compile-execute separation model imo. There's a certain pattern of sawing at the tree branch you're sitting on that you can fall into when digging too deep in emacs or a smalltalk image…