> I see this differently. If you compose a timestamp with a value, it is still a value. This is the essence of temporal data modelling and accounting. I agree

> I see this differently. If you compose a timestamp with a value, it is still a value. This is the essence of temporal data modelling and accounting. I agree completely that composing a timestamp with a value is still a value. I think the concept of assignment (values changing over time) is not the same thing as a timestamp at all; a timestamp doesn't represent state in the same way that mutability does. > The idea is however to avoid state whenever possible, pushing it to the edges. Yeah, this is where I think the problem lies. Saying "avoid state" isn't particularly helpful, especially if there is a certain amount of state that is essential and necessary. What should I do with the state that is required? What does it mean to push state to the edges, and in what cases does pushing state to the edges simplify my code? What if pushing the state causes complications by having to introduce more complex communication or more complex ordering between the elements of a system? I feel like one of the implicit suggestions when someone says to avoid state is that there is unnecessary state hanging around. But in practice, while there is sometimes redundant state, most programmers I've worked with are pretty conscientious about duplicating data. Most of the imperative production code I've worked with doesn't have a lot of redundant or duplicated state, it is already designed to minimize the amount of state. I love writing functional code when I can, it does feel simpler and easy to reason about. The two reasons I can't always write functional code are: performance and necessary state. Performance for functional constructs in various languages is improving, but it's still extremely common for functional designs to be very slow compared to equivalent imperative stateful designs. (And I do a lot of high performance computing as part of my current job.) And we need a better philosophy than just "avoid it" when it comes to all the necessary, unavoidable state.