The multiplicity is important if you see an array as a bag, i.e. a multiset. Some may reasonably expect the pairwise difference, which is indeed a default mode

The multiplicity is important if you see an array as a bag, i.e. a multiset. Some may reasonably expect the pairwise difference, which is indeed a default mode for vectors and matrixes (even C++ has one, `std::valarray`). There are also tons of implementation concerns I haven't ever dabbled.