It seems f0 and f1 dont have to be aggregate functions. For instance in the example you are using :: . You can also use the join operator , . The quewtion is, is the doc incomplete because my understanding is aggregate function gives an atom by taking in a list. http://code.kx.com/wiki/Reference/wj
The word “aggregate” is probably used more liberally here.
:: and , are in some sense “aggregate” functions – not aggregations that produce atomic values, but that produce vectors as results. The fact that one is allowed to have “nested lists” in a table structure permits such liberal “aggregates” I guess.