An application I'm considering writing needs to show a text that a user has edited at a particular time.
So consider if we have a text the user is editing from Time A to Time X, and I want to show what it looked like at Time L.
This text can be for a long running process, and it can be theoretically big, therefore it is not going to work just the brute solution of I will save what it is like at every keystroke - or well it might work but not very well.
But I'm betting there is probably some algorithm for how to handle this problem that I'm unfamiliar with such that basically I take Time L, take all the diffs from start of the text as an empty string at Time A and give me the actual resulting text.
I guess another way to think about it would be that it each Time in our time series has a keystroke associated with it, and then Time L just replays everything from Time A to L to get what the value of Text should be at Time L.
I hope this has been clear because often people seem to think I am unclear about these kinds of things.