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

NAME

  set_difference  - Basic set operation for sorted sequences.

SYNOPSIS

  #include <algorithm>

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

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

DESCRIPTION

  The set_difference algorithm constructs a sorted difference that includes
  copies of the elements that are present in the range [first1, last1) but
  are not present in the range [first2, last2).  It returns the end of the
  constructed range.

  As an example, assume we have the following two sets:

  1 2 3 4 5

  and

  3 4 5 6 7

  The result of applying set_difference is the set:

  1 2

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

  set_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_symetric_difference algorithm to return a result that contains
  all elements that are not in common between the two sets.

COMPLEXITY

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

EXAMPLE

  //
  // set_diff.cpp
  //
   #include <algorithm>
   #include <set>
   #include <iostream.h>
  int main()
   {
     //Initialize some sets
    int a1[10] = {1,2,3,4,5,6,7,8,9,10};
    int a2[6]  = {2,4,6,8,10,12};
    set<int, less<int> > all(a1, a1+10), even(a2, a2+6),
                         odd;
     //Create an insert_iterator for odd
    insert_iterator<set<int, less<int> > >
                  odd_ins(odd, odd.begin());

     //Demonstrate set_difference
    cout << "The result of:" << endl << "{";
    copy(all.begin(),all.end(),
         ostream_iterator<int,char>(cout," "));
    cout << "} - {";
    copy(even.begin(),even.end(),
         ostream_iterator<int,char>(cout," "));
    cout << "} =" << endl << "{";
     set_difference(all.begin(), all.end(),
                   even.begin(), even.end(), odd_ins);
    copy(odd.begin(),odd.end(),
         ostream_iterator<int,char>(cout," "));
    cout << "}" << endl << endl;
    return 0;
   }
  Output :
  The result of:
  {1 2 3 4 5 6 7 8 9 10 } - {2 4 6 8 10 12 } =
  {1 3 5 7 9 }

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_union, set_intersection, set_symmetric_difference

STANDARDS CONFORMANCE

  ANSI X3J16/ISO WG21 Joint C++ Committee



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