In my view, the position "get a lot more cautious about source vs. derived data" sort of is a mystery .. and I can only see one thing: temporality. Time-value.
If the CPU has 'now' to consider, and now is Time value [t] and if [t]'s are all there is between states, then 'think about [t1 .. t2]' should be a standard op.
And isn't this the point about immutability, that it has to have had a Time value, to be of any value at all, anyway, to the user?
If the CPU has 'now' to consider, and now is Time value [t] and if [t]'s are all there is between states, then 'think about [t1 .. t2]' should be a standard op.
And isn't this the point about immutability, that it has to have had a Time value, to be of any value at all, anyway, to the user?