K does a thing (like J I think?) where it's scan/reduce returns each subsequence/intermediate-value as it goes which is what makes that problem so trivial in K.
If the verb argument of over/scan takes a single argument (rather than two), the adverbs will iterate to a fixed point. As before, "/" will return the final result and "\" returns all the intermediates.
For example:
+/1 2 3
6
+\1 2 3
1 3 6
*:/,,,0
0
*:\,,,0
(,,,0
,,0
,0
0)((⊃∘⍒0⌷⍉)⌷⊢)(+\,∘⍪,\)