Standard C++ LibraryCopyright 1996, Rogue Wave Software, Inc.

NAME

  set_union  - Basic set operation for sorted sequences.

SYNOPSIS

  #include <algorithm>

  template <class InputIterator1, class InputIterator2, class OutputIterator>
  OutputIterator
  set_union (InputIterator1 first1, InputIterator1 last1,
            InputIterator2 first2, InputIterator2 last2,
            OutputIterator result);

  template <class InputIterator1, class InputIterator2,
           class OutputIterator, class Compare>
  OutputIterator
  set_union (InputIterator1 first1, InputIterator1 last1,
            InputIterator2 first2, InputIterator2 last2,
            OutputIterator result, Compare comp);

DESCRIPTION

  The set_union algorithm constructs a sorted union of the elements from the
  two ranges.  It returns the end of the constructed range.  set_union is
  stable, that is, if an element is present in both ranges, the one from the
  first range is copied. The result of set_union is undefined if the result
  range overlaps with either of the original ranges.  Note that set_union
  does not merge the two sorted sequences.  If an element is present in both
  sequences, only the element from the first sequence is copied to result.
  (Use the merge algorithm to create an ordered merge of two sorted sequences
  that contains all the elements from both sequences.)

  set_union assumes that the sequences 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  comparisons are
  performed.

EXAMPLE

  //
  // set_unin.cpp
  //
   #include <algorithm>
   #include <set>
   #include <iostream.h>

  int main()
   {

     //Initialize some sets
    int a2[6]  = {2,4,6,8,10,12};
    int a3[4]  = {3,5,7,8};
    set<int, less<int> >  even(a2, a2+6),
                         result, small(a3,a3+4);

     //Create an insert_iterator for result
    insert_iterator<set<int, less<int> > >
                  res_ins(result, result.begin());

     //Demonstrate set_union
    cout << "The result of:" << endl << "{";
    copy(small.begin(),small.end(),
         ostream_iterator<int,char>(cout," "));
    cout << "} union {";
    copy(even.begin(),even.end(),
         ostream_iterator<int,char>(cout," "));
    cout << "} =" << endl << "{";
     set_union(small.begin(), small.end(),
             even.begin(), even.end(), res_ins);
    copy(result.begin(),result.end(),
         ostream_iterator<int,char>(cout," "));
    cout << "}" << endl << endl;

    return 0;
   }

  Output :
  The result of:
  {3 5 7 8 } union {2 4 6 8 10 12 } =
  {2 3 4 5 6 7 8 10 12 }

WARNING

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

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

  instead of :

  set<int>

SEE ALSO

  includes, set, set_intersection, set_difference, set_symmetric_difference

STANDARDS CONFORMANCE

  ANSI X3J16/ISO WG21 Joint C++ Committee



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