reduce

Performs a reduction operation on the elements of this seq. This is equivalent to:

G? result = null;
bool found = false;
foreach (G g in seq) {
    if (!found) {
        result = g;
        found = true;
    } else {
        result = accumulator(g, result);
    }
}
return found ? new Optional<G>.of(result) : new Optional<G>.empty();

but is not constrained to execute sequentially.

This is a terminal operation.

Parameters:

accumulator

an associative, non-interfering, and stateless function for combining two values

Returns:

a future of the result of the reduction