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


NAME
     set_intersection

      - A basic set operation for constructing a sorted intersec-
     tion.



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



DESCRIPTION
     The set_intersection algorithm constructs a sorted intersec-
     tion  of elements from the two ranges. It returns the end of
     the constructed range. When it finds an element  present  in
     both ranges, set_intersection always copies the element from
     the first range into result. This means that the  result  of
     set_intersection is guaranteed to be stable.   The result of
     set_intersection is undefined if the result  range  overlaps
     with either of the original ranges.

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



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



EXAMPLE
     //
     // set_intr.cpp
     //
     #include <algorithm>
     #include <set>
     #include <iostream>
     using namespace std;
     int main()
      {

     //Initialize some sets
     int a1[10] = {1,3,5,7,9,11};
     int a3[4]  = {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_intersection
     cout << "The result of:" << endl << "{";
     copy(small.begin(),small.end(),
         ostream_iterator<int,char>(cout," "));
     cout << "} intersection {";
     copy(odd.begin(),odd.end(),
         ostream_iterator<int,char>(cout," "));
     cout << "} =" << endl << "{";
     set_intersection(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 result of:
     {3 5 7 8 } intersection {1 3 5 7 9 11 } =
     {3 5 7 }


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_difference,
     set_symmetric_difference

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