C++ STL: Why is there no upper_bound equivalent that retrieves the greatest element that is not greater than a specific key?

C++ STL: Why is there no upper_bound equivalent that retrieves the
greatest element that is not greater than a specific key?

References

Reference NO 1

http://stackoverflow.com/questions/15189194/c-stl-why-is-there-no-upper-bound-equivalent-that-retrieves-the-greatest-elem

Reference NO 2

http://stackoverflow.com/questions/11381487/c-stl-algorithms-upper-bound-that-is-not-strictly-greater

Reference NO 3

http://www.cplusplus.com/reference/set/multiset/

Reference NO 4

http://en.wikipedia.org/wiki/Associative_containers_(C%2B%2B)

Reference NO 5

http://www.boost.org/doc/libs/1_39_0/libs/multi_index/doc/tutorial/basics.html

Reference NO 6

http://msdn.microsoft.com/en-us/library/e8wh7665.aspx

Reference NO 7

http://en.cppreference.com/w/cpp/algorithm/lower_bound

Reference NO 8

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