OutputIterator
set_symmetric_difference (InputIterator source1Beg,
                             InputIterator source1End,
                          InputIterator source2Beg,
                             InputIterator source2End,
                          OutputIterator destBeg)

set_symmetric_difference (InputIterator source1Beg, 
                              InputIterator source1End,
                          InputIterator source2Beg,
                              InputIterator source2End,
                          OutputIterator destBeg, BinaryPredicate op)