rlundo

A crazy, but cool idea to implement this is using fork: https://github.com/thomasballinger/rlundo

Here's another implementation of what's described above, it forks on each invocation of readline to provide undo for interactive interpreters. https://github.com/thomasballinger/rlundo

I've played with prototypes of this by calling fork on IPython to take snapshots of interpreter state https://github.com/thomasballinger/rlundo/blob/master/readme... but if you can't serialize state fully, rerunning from the top (bpython's approach) can work, or rerunning as a dependency dag shows is necessary (my current employer Observable's approach) works nicely.

If anyone wants to walk through these ideas more slowly I write about them in http://ballingt.com/interactive-interpreter-undo and implement this in https://github.com/thomasballinger/rlundo but as you say, eventually decided I had to implement an interpreter for which serialization of state was more efficient and all external resources had amenable interfaces http://dalsegno.ballingt.com/

The Jupyter models is hard for this, but if you only allow in-order execution (like a repl, say IPython whose kernel is used in Jupyter) you could do something like this. We tried plugging in the rlundo tool https://github.com/thomasballinger/rlundo to IPython, it works ok, see http://ballingt.com/interactive-interpreter-undo/ for the long story. I wanted something like this for live programming and felt like I needed to write my own interpreter because the behavior you need is so different: http://dalsegno.ballingt.com

It is interesting to use fork() to snapshot application state. It seems so high-level and powerful (Compared to other C/POSIX level stuff - so I'm not comparing it to Scheme/Lisp/"your favorite high/low level environment" here!). We may collect some other examples here - just for fun: - I know that Redis does this (RDB snaphots) too, while the child process saves the actual snapshot, the parent can operate continously relying on the system provided copy on write mechanism - I have also found this: https://github.com/thomasballinger/rlundo - It overwrites readline library to get undo function in any REPL using it Other examples?

Here's an idea that I like (so much that I wrote an implementation): use LD_PRELOAD to swap out readline with version that forks on each input. Kill the forked child process and you have undo! https://github.com/thomasballinger/rlundo post: http://ballingt.com/interactive-interpreter-undo/#hacking-fo...