E = duration.empty () returns a $0\times 0$ empty duration array. duration.empty (m, n, …) or duration.empty (sz) returns an empty duration array of the requested size, which must have at least one dimension equal to zero. A lone dimension gives a square size, so duration.empty (3) is an error while duration.empty (0) is $0\times 0$. As for zeros, a negative dimension counts as zero, and a size vector with nothing in it names no size and gives $0\times 0$.

Source Code: duration