> This seems powerful. Is "doing the minimal amount of work" provably true, or is this just a way of saying that it's usually fast? It is powerful, it's not pr

> This seems powerful. Is "doing the minimal amount of work" provably true, or is this just a way of saying that it's usually fast? It is powerful, it's not provably true (or even generally true ...) "Dependencies" are Excel-style recomputation. The code c::a+b says (1) that c depends on the value of a and the value of b, and that (2) whenever you evaluate c, if 'a' or 'b' has changed since the last evaluation, you re-evaluate the expression and assign it to c; otherwise return the cached value. So, multiple changes to a or b will not trigger recomputation - only the eventual use of C; However, it's possible that 'a' is a vector of length 1,000,000 and so is b, and only one element in a was changed - K would still do a million addition operations. "Triggers" work the other way arround: You used to set a trigger on 'a' by assigning a trigger function a..t:{[d,i] ...} which would receive as argument the post-assignment value 'd' and the indexes assigned 'i'; You could use these to do a minimal update of whatever logically depends on a; However, the triggers DO fire on every change unlike dependencies. > For example, let's say that I have a list of numbers that I have sorted using bubble sort. Now I change one of the numbers. Would the update be O(log N)? I think there is no way to guarantee O(log n) anyway in this case - change the first element to be in the middle - requires at least O(n) changes on either a sequential or singly/doubly linked list. But assuming you're talking about say, a heap structure - the answer would be "No" for a dependency, and "If you implement it yourself" for a trigger. > This sounds like Svelte avant la lettre. I'm really curious how the updates are performed. Sort of. It was a native GUI, incredibly fast, and incredibly bare bones - it was eventually dropped because all the customers were making web front ends anyway. Being a native GUI, I suspect (but don't know) it was using the triggers to mark damage regions and let the windowing system take over from there.