Building on the previous exercise, implement higher-level union, intersection, and difference functions that operate on ordered sets. Note that these should not be members of the ordered_set class, but rather stand-alone functions: they should be independent of the details of list_set or any other particular ordered_set. So, for example, union(A, B, C) should verify that A is empty, and then add to it all the elements found in B or C. Explain, for each of C++, Java, and C#, how to handle the comparison of elements.