Return a past-the-end const iterator for this set.
Declared in <bslstl_unorderedset.h>
unordered_set<KEY, HASH, EQUAL, ALLOCATOR>::const_iterator
cend() const noexcept;Return an iterator providing non-modifiable access to the past-the-end element (in the sequence of value_type objects) maintained by this set.
past-the-end const iterator