3.5.4 Reduce actions

The subaction of a reduce action takes two input values of the same type as the elements, and produces an output also of the same type. The reduce action applies the subaction sequentially on pairs on elements until the final result, which is the same type as the elements, is produced.

Figure 6: The process of reduce actions

The process is illustrated in Figure 6.

The input collection is ordered. The output is not a collection but a single element.