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 <H2>set_difference()</H2>
 <P><B>Library:</B>&nbsp;&nbsp;<A HREF="2-9.html">Algorithms</A></P>

 <PRE><HR><B><I>Function</I></B><HR></PRE>

 <UL>
 <LI><A HREF="#sec1">Local Index</A></LI>
 <LI><A HREF="#sec2">Summary</A></LI>
 <LI><A HREF="#sec3">Synopsis</A></LI>
 <LI><A HREF="#sec4">Description</A></LI>
 <LI><A HREF="#sec5">Complexity</A></LI>
 <LI><A HREF="#sec6">Example</A></LI>
 <LI><A HREF="#sec7">See Also</A></LI>
 <LI><A HREF="#sec8">Standards Conformance</A></LI>
 </UL>
 <A NAME="sec1"><H3>Local Index</H3></A>
 No Entries
 <A NAME="sec2"><H3>Summary</H3></A>
 <P>A basic set operation (algorithm) for constructing a sorted difference</P>
 <A NAME="sec3"><H3>Synopsis</H3></A>

 <PRE>#include &lt;algorithm&gt;

 namespace std {
   template &lt;class InputIterator1, class InputIterator2,
             class OutputIterator&gt;
   OutputIterator
   set_difference(InputIterator1 start1,
                  InputIterator1 finish1,
                  InputIterator2 start2,
                  InputIterator2 finish2,
                  OutputIterator result);
   template &lt;class InputIterator1, class InputIterator2,
             class OutputIterator, class Compare&gt;
   OutputIterator
   set_difference(InputIterator1 start1,
                  InputIterator1 finish1,
                  InputIterator2 start2,
                  InputIterator2 finish2,
                  OutputIterator result,
                  Compare comp);
 }
 </PRE>
 <A NAME="sec4"><H3>Description</H3></A>
 <P>The <SAMP>set_difference()</SAMP> algorithm constructs a sorted difference that includes copies of the elements that are present in the range <SAMP>[start1, finish1)</SAMP> but are not present in the range <SAMP>[start2, finish2)</SAMP>. It returns the end of the constructed range. </P>
 <P>As an example, assume we have the following two sets:</P>
 <P><SAMP>1 2 3 4 5</SAMP></P>
 <P>and </P>
 <P><SAMP>3 4 5 6 7</SAMP></P>
 <P>The result of applying <SAMP>set_difference()</SAMP> is the set:</P>
 <P><SAMP>1 2</SAMP></P>
 <P>The result of <SAMP>set_difference()</SAMP> is undefined if the result range overlaps with either of the original ranges. </P>
 <P><SAMP>set_difference()</SAMP> assumes that the ranges are sorted using <SAMP>operator&lt;()</SAMP>, unless an alternative comparison function object (<SAMP>comp</SAMP>) is provided. </P>
 <P>Use the <SAMP>set_symetric_difference()</SAMP> algorithm to obtain a result that contains all elements that are not in common between the two sets.</P>
 <A NAME="sec5"><H3>Complexity</H3></A>
 <P>At most <SAMP>((finish1 - start1) + (finish2 - start2)) * 2 -1</SAMP> comparisons are performed.</P>
 <A NAME="sec6"><H3>Example</H3></A>

 <UL><PRE>//
 //  set_diff.cpp
 //

 #include &lt;algorithm&gt;
 #include &lt;set&gt;
 #include &lt;iostream&gt;

 int main ()
 {
 #ifndef _RWSTD_NO_NAMESPACE
   using namespace std;
 #endif


   // 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&lt;int, less&lt;int&gt;,allocator&lt;int&gt; &gt; all(a1+0, a1+10),
                                       even(a2+0, a2+6), odd;

   // Create an insert_iterator for odd.

   insert_iterator&lt;set &lt;int, less&lt;int&gt;,allocator&lt;int&gt; &gt; &gt;
                  odd_ins(odd, odd.begin());

   // Demonstrate set_difference.

   cout &lt;&lt; "The result of:" &lt;&lt; endl &lt;&lt; "{";
   copy(all.begin(),all.end(),
        ostream_iterator&lt;int,char,char_traits&lt;char&gt; &gt;
                        (cout," "));
   cout &lt;&lt; "} - {";
   copy(even.begin(),even.end(),
        ostream_iterator&lt;int,char,char_traits&lt;char&gt; &gt;
                        (cout," "));
   cout &lt;&lt; "} =" &lt;&lt; endl &lt;&lt; "{";
   set_difference(all.begin(), all.end(), even.begin(),
                  even.end(), odd_ins);
   copy(odd.begin(),odd.end(),
        ostream_iterator&lt;int,char,char_traits&lt;char&gt; &gt;
                        (cout," "));
   cout &lt;&lt; "}" &lt;&lt; endl &lt;&lt; endl;

   return 0;
 }


 Program Output:
 </PRE></UL>
 <UL><PRE>The result of:
 {1 2 3 4 5 6 7 8 9 10 } - {2 4 6 8 10 12 } =
 {1 3 5 7 9 }

 </PRE></UL>
 <A NAME="sec7"><H3>See Also</H3></A>
 <P><SAMP><A HREF="includes.html">includes()</A></SAMP>, <A HREF="iterators.html">Iterators</A>, <SAMP><A HREF="set-union.html">set_union()</A></SAMP>, <SAMP><A HREF="set-intersection.html">set_intersection()</A></SAMP>, <SAMP><A HREF="set-symmetric-difference.html">set_symmetric_difference()</A></SAMP></P>
 <A NAME="sec8"><H3>Standards Conformance</H3></A>
 <P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 25.3.5.4</I></P>

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	<H2>set_difference()</H2>
	<P><B>Library:</B>  <A HREF="2-9.html">Algorithms</A></P>

	<PRE><HR><B><I>Function</I></B><HR></PRE>

	<UL>
	<LI><A HREF="#sec1">Local Index</A></LI>
	<LI><A HREF="#sec2">Summary</A></LI>
	<LI><A HREF="#sec3">Synopsis</A></LI>
	<LI><A HREF="#sec4">Description</A></LI>
	<LI><A HREF="#sec5">Complexity</A></LI>
	<LI><A HREF="#sec6">Example</A></LI>
	<LI><A HREF="#sec7">See Also</A></LI>
	<LI><A HREF="#sec8">Standards Conformance</A></LI>
	</UL>
	<A NAME="sec1"><H3>Local Index</H3></A>
	No Entries
	<A NAME="sec2"><H3>Summary</H3></A>
	<P>A basic set operation (algorithm) for constructing a sorted difference</P>
	<A NAME="sec3"><H3>Synopsis</H3></A>

	<PRE>#include <algorithm>

	namespace std {
	template <class InputIterator1, class InputIterator2,
	class OutputIterator>
	OutputIterator
	set_difference(InputIterator1 start1,
	InputIterator1 finish1,
	InputIterator2 start2,
	InputIterator2 finish2,
	OutputIterator result);
	template <class InputIterator1, class InputIterator2,
	class OutputIterator, class Compare>
	OutputIterator
	set_difference(InputIterator1 start1,
	InputIterator1 finish1,
	InputIterator2 start2,
	InputIterator2 finish2,
	OutputIterator result,
	Compare comp);
	}
	</PRE>
	<A NAME="sec4"><H3>Description</H3></A>
	<P>The <SAMP>set_difference()</SAMP> algorithm constructs a sorted difference that includes copies of the elements that are present in the range <SAMP>[start1, finish1)</SAMP> but are not present in the range <SAMP>[start2, finish2)</SAMP>. It returns the end of the constructed range. </P>
	<P>As an example, assume we have the following two sets:</P>
	<P><SAMP>1 2 3 4 5</SAMP></P>
	<P>and </P>
	<P><SAMP>3 4 5 6 7</SAMP></P>
	<P>The result of applying <SAMP>set_difference()</SAMP> is the set:</P>
	<P><SAMP>1 2</SAMP></P>
	<P>The result of <SAMP>set_difference()</SAMP> is undefined if the result range overlaps with either of the original ranges. </P>
	<P><SAMP>set_difference()</SAMP> assumes that the ranges are sorted using <SAMP>operator<()</SAMP>, unless an alternative comparison function object (<SAMP>comp</SAMP>) is provided. </P>
	<P>Use the <SAMP>set_symetric_difference()</SAMP> algorithm to obtain a result that contains all elements that are not in common between the two sets.</P>
	<A NAME="sec5"><H3>Complexity</H3></A>
	<P>At most <SAMP>((finish1 - start1) + (finish2 - start2)) * 2 -1</SAMP> comparisons are performed.</P>
	<A NAME="sec6"><H3>Example</H3></A>

	<UL><PRE>//
	// set_diff.cpp
	//

	#include <algorithm>
	#include <set>
	#include <iostream>

	int main ()
	{
	#ifndef _RWSTD_NO_NAMESPACE
	using namespace std;
	#endif


	// 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>,allocator<int> > all(a1+0, a1+10),
	even(a2+0, a2+6), odd;

	// Create an insert_iterator for odd.

	insert_iterator<set <int, less<int>,allocator<int> > >
	odd_ins(odd, odd.begin());

	// Demonstrate set_difference.

	cout << "The result of:" << endl << "{";
	copy(all.begin(),all.end(),
	ostream_iterator<int,char,char_traits<char> >
	(cout," "));
	cout << "} - {";
	copy(even.begin(),even.end(),
	ostream_iterator<int,char,char_traits<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,char_traits<char> >
	(cout," "));
	cout << "}" << endl << endl;

	return 0;
	}


	Program Output:
	</PRE></UL>
	<UL><PRE>The result of:
	{1 2 3 4 5 6 7 8 9 10 } - {2 4 6 8 10 12 } =
	{1 3 5 7 9 }

	</PRE></UL>
	<A NAME="sec7"><H3>See Also</H3></A>
	<P><SAMP><A HREF="includes.html">includes()</A></SAMP>, <A HREF="iterators.html">Iterators</A>, <SAMP><A HREF="set-union.html">set_union()</A></SAMP>, <SAMP><A HREF="set-intersection.html">set_intersection()</A></SAMP>, <SAMP><A HREF="set-symmetric-difference.html">set_symmetric_difference()</A></SAMP></P>
	<A NAME="sec8"><H3>Standards Conformance</H3></A>
	<P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 25.3.5.4</I></P>

	<BR>
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