Standard C++	Library
 		 Copyright 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