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 <H2>set_union()</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 union</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_union(InputIterator1 start1, InputIterator1 finish1,
             InputIterator2 start2, InputIterator2 finish2,
             OutputIterator result);

   template &lt;class InputIterator1, class InputIterator2,
             class OutputIterator, class Compare&gt;
   OutputIterator
   set_union(InputIterator1 start1, InputIterator1 finish1,
             InputIterator2 start2, InputIterator2 finish2,
             OutputIterator result, Compare comp);
 }
 </PRE>
 <A NAME="sec4"><H3>Description</H3></A>
 <P>The <SAMP>set_union()</SAMP> algorithm constructs a sorted union of the elements from the two ranges. It returns the end of the constructed range. <SAMP>set_union()</SAMP> is stable, which means that if an element is present in both ranges, the one from the first range is copied. The result of <SAMP>set_union()</SAMP> is undefined if the result range overlaps with either of the original ranges. Note that <SAMP>set_union()</SAMP> 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 <SAMP>result</SAMP>. (Use the <SAMP><A HREF="merge.html">merge()</A></SAMP> algorithm to create an ordered merge of two sorted sequences that contains all the elements from both sequences.)</P>
 <P><SAMP>set_union()</SAMP> assumes that the sequences are sorted using <SAMP>operator&lt;()</SAMP>, unless an alternative comparison function object (<SAMP>comp</SAMP>) is provided. </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_unin.cpp
 //

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

 int main ()
 {
     _USING (namespace std);

     typedef set&lt;int, less&lt;int&gt;,allocator&lt;int&gt; &gt; Set;

     // Initialize sets.

     int a1[] = {2, 4, 6, 8, 10, 12};
     int a2[] = {3, 5, 7, 8};

     Set s1 (a1, a1 + sizeof a1 / sizeof *a1);
     Set s2 (a2, a2 + sizeof a2 / sizeof *a2);
     Set result;

     // Create an insert_iterator for result.

     insert_iterator&lt;Set&gt; res_ins (result, result.begin ());

     // Compute union of two sets.

     set_union (s2.begin (), s2.end (),
                s1.begin (), s1.end (), res_ins);

     // Display result on standard output.

     typedef ostream_iterator&lt;int, char, char_traits&lt;char&gt; &gt;
             OSIter;

     cout &lt;&lt; "The result of:" &lt;&lt; endl &lt;&lt; "{ ";
     copy (s2.begin (),s2.end (), OSIter (cout," "));
     cout &lt;&lt; "} union { ";
     copy (s1.begin (),s1.end (), OSIter (cout," "));
     cout &lt;&lt; "} =" &lt;&lt; endl &lt;&lt; "{ ";
     copy (result.begin (),result.end (), OSIter (cout," "));
     cout &lt;&lt; "}" &lt;&lt; endl &lt;&lt; endl;

     return 0;
 }


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

 </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-intersection.html">set_intersection()</A></SAMP>, <SAMP><A HREF="set-difference.html">set_difference()</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 25.3.5.2</I></P>

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	<H2>set_union()</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 union</P>
	<A NAME="sec3"><H3>Synopsis</H3></A>

	<PRE>#include <algorithm>

	namespace std {
	template <class InputIterator1, class InputIterator2,
	class OutputIterator>
	OutputIterator
	set_union(InputIterator1 start1, InputIterator1 finish1,
	InputIterator2 start2, InputIterator2 finish2,
	OutputIterator result);

	template <class InputIterator1, class InputIterator2,
	class OutputIterator, class Compare>
	OutputIterator
	set_union(InputIterator1 start1, InputIterator1 finish1,
	InputIterator2 start2, InputIterator2 finish2,
	OutputIterator result, Compare comp);
	}
	</PRE>
	<A NAME="sec4"><H3>Description</H3></A>
	<P>The <SAMP>set_union()</SAMP> algorithm constructs a sorted union of the elements from the two ranges. It returns the end of the constructed range. <SAMP>set_union()</SAMP> is stable, which means that if an element is present in both ranges, the one from the first range is copied. The result of <SAMP>set_union()</SAMP> is undefined if the result range overlaps with either of the original ranges. Note that <SAMP>set_union()</SAMP> 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 <SAMP>result</SAMP>. (Use the <SAMP><A HREF="merge.html">merge()</A></SAMP> algorithm to create an ordered merge of two sorted sequences that contains all the elements from both sequences.)</P>
	<P><SAMP>set_union()</SAMP> assumes that the sequences are sorted using <SAMP>operator<()</SAMP>, unless an alternative comparison function object (<SAMP>comp</SAMP>) is provided. </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_unin.cpp
	//

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

	int main ()
	{
	_USING (namespace std);

	typedef set<int, less<int>,allocator<int> > Set;

	// Initialize sets.

	int a1[] = {2, 4, 6, 8, 10, 12};
	int a2[] = {3, 5, 7, 8};

	Set s1 (a1, a1 + sizeof a1 / sizeof *a1);
	Set s2 (a2, a2 + sizeof a2 / sizeof *a2);
	Set result;

	// Create an insert_iterator for result.

	insert_iterator<Set> res_ins (result, result.begin ());

	// Compute union of two sets.

	set_union (s2.begin (), s2.end (),
	s1.begin (), s1.end (), res_ins);

	// Display result on standard output.

	typedef ostream_iterator<int, char, char_traits<char> >
	OSIter;

	cout << "The result of:" << endl << "{ ";
	copy (s2.begin (),s2.end (), OSIter (cout," "));
	cout << "} union { ";
	copy (s1.begin (),s1.end (), OSIter (cout," "));
	cout << "} =" << endl << "{ ";
	copy (result.begin (),result.end (), OSIter (cout," "));
	cout << "}" << endl << endl;

	return 0;
	}


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

	</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-intersection.html">set_intersection()</A></SAMP>, <SAMP><A HREF="set-difference.html">set_difference()</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 25.3.5.2</I></P>

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