Forum Discussion
Post ProdigyRolling accumulation
Post ProdigyI like the gen version as i can understand it, I get the accer,, but m_d , you really must be good
at visualisig things as I have taken it apart and see how it works, but would never have been able to
build it.
Resident RockstarHi Dicken,
Once you know this trick it is easier to understand 😉 let me try to explain the inner workings.
The seed s is a record containing two fields, a and b, both assigned an empty list.
At each iteration:
-
Think of the field
aas a rolling window that holds up to the last four values that were seen. It’s updated by appending the current value{v}fromalistto the previous list states[a], then trimmed to keep only the most recent four itemsList.LastN(..., 4) -
Once
ais updated, we calculate its total using{List.Sum(a)}. That number gets added (apended) to the previous list states[b], which is a growing list of those running totals.
After the accumulation completes, the field [b] contains the full sequence. A list showing what the sum of the last four values was after every step.
I hope this helps to visualize the process, Richard.