> Whereas "live coding" is about some programmer coding "live" in front of an audience, live programming is about receiving continuous comprehensible feedback about your program edits in the context of a running program. Quite a huge difference in meaning with very different goals!
Yes that's what I mean! A tiny difference in the terms we use: live coding vs live programming. That's why it's confusing to people.
> Why should we back off and invent yet another new term to describe the new experience whose original term was hijacked to descirbe old experiences because people couldn't understand the new one? Crazy!
Sometimes you have to cut your losses ;-) Another reason why I dislike the term "live programming" is because it confuses two separate concepts: continuous feedback and rich feedback. Conventional debugging is pressing a button to run your code and see what the result is. Instead of just displaying the result, you could display the entire execution trace (time traveling debuggers). You could write unit tests and display which passed and which failed. You could output some visualization of some data structure in the program. For a game you could output a series of frames overlaid on each other (like Bret Victor does). Then you have type checking, for numerical code sensitivity to floating point bit width, performance profiling, etc. This is all about giving different kinds of feedback. Continuous feedback is about getting feedback without having to press a button. Classical live programming is running the program continuously and continuously displaying its output. This is the continuous feedback version of ordinary debugging. Automated background unit test runners are the continuous version of unit testing. In the same way you have a continuous version of the other debugging techniques. Both continuous feedback and rich feedback are very valuable, and although they are stronger together they are separate concepts. Perhaps it would be a good idea to have separate words for them, that would certainly greatly clarify "live programming".
> but you can always "record" the input event history of your program and re-exec the entire program on a code change; i.e. there is an inefficient baseline. You still have problems with causality between program output and input; e.g. consider the user clicking a button that no longer exists or moved!
Yes, this is robust to internal data structure changes but no longer robust to UI changes. Viewing a program as a series of event stream transformers and time varying values as in FRP may help a bit. At the lowest level you have a stream of mouse clicks on pixel (x,y) and keyboard events with keycode k. Then the UI toolkit transforms that stream of events to event streams on UI elements: click on button "delete", text input to textfield "email address". Then that gets transformed to logical operations and data: delete_address_book_entry(...) and email_address. Then that gets transformed to the complete time varying high level state of the entire program (address_book_database). You can try to transport the state on each of the different levels, but in the end I think a completely automated solution is impossible. You are going to need domain specific info on how to do schema migration in the general case. For live programming that may not be worth it because you can just start over with a fresh state, but for things like web site databases you don't want to lose data so you have to manually migrate. [tangent: Currently there are a lot of ad-hoc solutions to this e.g. never remove an attribute from your data model, and when you add new attributes make sure all code works even if that attribute is missing. Reddit even goes so far as to structure its entire database as "key,attribute,value" triples instead of using a structured schema so that the schema never needs to change, but of course this just moves the problem from the database into the code that talks to the database. A principled approach where you write an explicit function to migrate your data from schema version n to schema version n+1 would work better. That migration function takes the entire state/database with schema n as input and produces an entire new state/database with schema n+1. When the state/database is large this would take too long to do it in one pass, but with laziness that can be done on-demand.]
You don't need to limit yourself to running one instance of the program. You could record multiple input sequences representing multiple testing scenarios, and display the results of running each of them, or even display each of them being continuously performed so that you can see all the steps in between. In any case as you say there is lots of work still to be done.