Caterpillar

In addition to editing values of arbitrary types, I'd like to have functionality to generate new values of those types too. Imagine libraries defining specially annotated functions, that then show up in the editor as buttons, or other UI elements.

Caterpillar is initially focused on simple games as a use case, so that's a lot of what I'm thinking about. A game engine could provide functions to generate random sprites or sounds. That would get you started with your game a lot quicker! And it fits with Caterpillar's theme of immediacy.

Need a randomized explosion sound? Click a button. Don't like it? Tweak it right in your editor, using the UI element provided by the game engine. Need more variety? Click that button a few more times. All this sounds pretty great to me. And it's applicable to other areas too. Just think about frameworks like Ruby on Rails that come with command-line tools to generate stuff for you.