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                       Standard C++ Library
             Copyright 1998, Rogue Wave Software, Inc.


NAME
     set_symmetric_difference

      - A basic set operation for constructing a sorted symmetric
     difference.



SYNOPSIS
     #include <algorithm>
     template <class InputIterator1, class InputIterator2,
              class OutputIterator>
      OutputIterator
         set_symmetric_difference (InputIterator1 first1,
                                  InputIterator1 last1,
                                  InputIterator2 first2,
                                  InputIterator2 last2,
                                  OutputIterator result);
     template <class InputIterator1, class InputIterator2,
              class OutputIterator, class Compare>
      OutputIterator
         set_symmetric_difference (InputIterator1 first1,
                                  InputIterator1 last1,
                                  InputIterator2 first2,
                                  InputIterator2 last2,
                                  OutputIterator result,
                                  Compare comp);



DESCRIPTION
     set_symmetric_difference  constructs  a   sorted   symmetric
     difference  of  the elements from the two ranges. This means
     that the constructed range includes copies of  the  elements
     that  are  present  in  the  range  [first1, last1) (but not
     present in the range [first2, last2)) and copies of the ele-
     ments that are present in the range [first2, last2) (but not
     in the range [first1, last1)). It returns  the  end  of  the
     constructed range.

     For example, suppose we have two sets:

     1 2 3 4 5

     and

     3 4 5 6 7

     The set_symmetric_difference of these two sets is:

     1 2 6 7

     The result of set_symmetric_difference is undefined  if  the
     result range overlaps with either of the original ranges.

     set_symmetric_difference assumes that the ranges are  sorted
     using  the default comparison operator less than (<), unless
     an alternative comparison operator (comp) is provided.

     Use  the  set_symmetric_difference  algorithm  to  return  a
     result  that includes elements that are present in the first
     set and not in the second.



COMPLEXITY
     At most ((last1 - first1) + (last2 - first2)) *  2  -1  com-
     parisons are performed.



EXAMPLE
     //
     // set_s_di.cpp
     //
     #include<algorithm>
     #include<set>
     #include <istream.h>
     using namespace std;

     int main()
      {

     //Initialize some sets
     int a1[] = {1,3,5,7,9,11};
     int a3[] = {3,5,7,8};
     set<int, less<int> > odd(a1+0,a1+6), result,
        small(a3+0,a3+4);
     //Create an insert_iterator for result
     insert_iterator<set<int, less<int> > >
        res_ins(result, result.begin());
     //Demonstrate set_symmetric_difference
     cout << "The symmetric difference of:" << endl << "{";
     copy(small.begin(),small.end(),
         ostream_iterator<int,char>(cout," "));
     cout << "} with {";
     copy(odd.begin(),odd.end(),
         ostream_iterator<int,char>(cout," "));
     cout << "} =" << endl << "{";
     set_symmetric_difference(small.begin(), small.end(),
                             odd.begin(), odd.end(), res_ins);
     copy(result.begin(),result.end(),
         ostream_iterator<int,char>(cout," "));
     cout << "}" << endl << endl;
     return 0;
      }


     Program Output



     The symmetric difference of:
     {3 5 7 8 } with {1 3 5 7 9 11 } =
     {1 8 9 11 }



WARNINGS
     If your compiler does not support default  template  parame-
     ters,  then  you  always need to supply the Compare template
     argument and the Allocator template argument. For  instance,
     you need to write:

     set<int, less<int>, allocator<int> >

     instead of:

     set<int>

     If your compiler does not support namespaces,  then  you  do
     not need the using declaration for std.



SEE ALSO
     includes, set, set_union,_set_intersection, set_difference

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