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 <H2>equal()</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">Standards Conformance</A></LI>
 </UL>
 <A NAME="sec1"><H3>Local Index</H3></A>
 No Entries
 <A NAME="sec2"><H3>Summary</H3></A>
 <P>Algorithm that compares two ranges of values for equality</P>
 <A NAME="sec3"><H3>Synopsis</H3></A>

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

 namespace std {
   template &lt;class InputIterator1, class InputIterator2&gt;
   bool equal(InputIterator1 start1, InputIterator1 finish1,
              InputIterator2 start2);

  template &lt;class InputIterator1, class InputIterator2,
            class BinaryPredicate&gt;
  bool equal(InputIterator1 start1, InputIterator1 finish1,
             InputIterator2 start2, BinaryPredicate
             binary_pred);
 }
 </PRE>
 <A NAME="sec4"><H3>Description</H3></A>
 <P>The <SAMP>equal()</SAMP> algorithm does a pairwise comparison of all of the elements in one range with all of the elements in another range to see if they match. The first version of <SAMP>equal()</SAMP> uses <SAMP>operator==()</SAMP> as the comparison function, and the second version allows you to specify a binary predicate as the comparison function. The first version returns <SAMP>true</SAMP> if all of the corresponding elements are equal to each other. The second version of <SAMP>equal()</SAMP> returns <SAMP>true</SAMP> if for each pair of elements in the two ranges, the result of applying the binary predicate is true. In other words, <SAMP>equal()</SAMP> returns <SAMP>true</SAMP> if both of the following are true:</P>
 <UL>
 <LI><P CLASS="LIST">There are at least as many elements in the second range as in the first</P></LI>
 <LI><P CLASS="LIST">For every iterator <SAMP>i</SAMP> in the range <SAMP>[start1, finish1)</SAMP> the following corresponding conditions hold: </P></LI>
 <P CLASS="LIST"><SAMP>*i == *(start2 + (i - start1))</SAMP></P>
 <P CLASS="LIST">or</P>
 <P CLASS="LIST"><SAMP>binary_pred(*i, *(start2 + (i - start1))) == true</SAMP></P>
 </UL>
 <P>If one of these conditions is not true, <SAMP>equal()</SAMP> returns <SAMP>false</SAMP>.</P>
 <P>This algorithm assumes that all iterators in the range <SAMP>[start2, start2 + (finish1 - start1)]</SAMP> are dereferenceable.</P>
 <A NAME="sec5"><H3>Complexity</H3></A>
 <P><SAMP>equal()</SAMP> performs at most <SAMP>finish1 - start1</SAMP> comparisons or applications of the predicate.</P>
 <A NAME="sec6"><H3>Example</H3></A>

 <UL><PRE>//
 // equal.cpp
 //

 #include &lt;algorithm&gt;    // equal
 #include &lt;functional&gt;
 #include &lt;iostream&gt;
 #include &lt;vector&gt;


 int main ()
 {
     // Typedef for convenience.
     typedef std::vector&lt;int, std::allocator&lt;int&gt; &gt; vector;

     typedef std::ostream_iterator &lt;vector::value_type, char,
                              std::char_traits&lt;char&gt; &gt; os_iter;

     const vector::value_type a1[] = { 1, 2, 3, 4 };
     const vector::value_type a2[] = { 1, 2, 4, 3 };

     // Set up two vectors.
     const vector v1(a1, a1 + sizeof a1 / sizeof *a1);
     const vector v2(a2, a2 + sizeof a2 / sizeof *a2);

     // Check for equality.
     bool same = std::equal(v1.begin(), v1.end(),
                            v2.begin());

     same = same &amp;&amp; std::equal(v1.begin(), v1.end(),
              v2.begin(), std::equal_to&lt;vector::value_type&gt;());

     // Output the sequences.
     std::cout &lt;&lt; "{ ";
     std::copy(v1.begin(), v1.end(), os_iter(std::cout, " "));

     std::cout &lt;&lt; "} == { ";
     std::copy(v2.begin(), v2.end(), os_iter(std::cout, " "));

     // Output the result.
     std::cout &lt;&lt; "} --&gt; " &lt;&lt; std::boolalpha
               &lt;&lt; same &lt;&lt; std::endl;

     return 0;
 }


 Program Output
 </PRE></UL>
 <UL><PRE>{ 1 2 3 4 } == { 1 2 4 3 } --&gt; false

 </PRE></UL>
 <A NAME="sec7"><H3>Standards Conformance</H3></A>
 <P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems --Programming Language C++, Section 25.1.8</I></P>

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	<A HREF="domain-error.html"><IMG SRC="images/bprev.gif" WIDTH=20 HEIGHT=21 ALT="Previous file" BORDER=O></A><A HREF="noframes.html"><IMG SRC="images/btop.gif" WIDTH=56 HEIGHT=21 ALT="Top of Document" BORDER=O></A><A HREF="booktoc.html"><IMG SRC="images/btoc.gif" WIDTH=56 HEIGHT=21 ALT="Contents" BORDER=O></A><A HREF="tindex.html"><IMG SRC="images/bindex.gif" WIDTH=56 HEIGHT=21 ALT="Index page" BORDER=O></A><A HREF="equal-range.html"><IMG SRC="images/bnext.gif" WIDTH=25 HEIGHT=21 ALT="Next file" BORDER=O></A><DIV CLASS="DOCUMENTNAME"><B>Apache C++ Standard Library Reference Guide</B></DIV>
	<H2>equal()</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">Standards Conformance</A></LI>
	</UL>
	<A NAME="sec1"><H3>Local Index</H3></A>
	No Entries
	<A NAME="sec2"><H3>Summary</H3></A>
	<P>Algorithm that compares two ranges of values for equality</P>
	<A NAME="sec3"><H3>Synopsis</H3></A>

	<PRE>#include <algorithm>

	namespace std {
	template <class InputIterator1, class InputIterator2>
	bool equal(InputIterator1 start1, InputIterator1 finish1,
	InputIterator2 start2);

	template <class InputIterator1, class InputIterator2,
	class BinaryPredicate>
	bool equal(InputIterator1 start1, InputIterator1 finish1,
	InputIterator2 start2, BinaryPredicate
	binary_pred);
	}
	</PRE>
	<A NAME="sec4"><H3>Description</H3></A>
	<P>The <SAMP>equal()</SAMP> algorithm does a pairwise comparison of all of the elements in one range with all of the elements in another range to see if they match. The first version of <SAMP>equal()</SAMP> uses <SAMP>operator==()</SAMP> as the comparison function, and the second version allows you to specify a binary predicate as the comparison function. The first version returns <SAMP>true</SAMP> if all of the corresponding elements are equal to each other. The second version of <SAMP>equal()</SAMP> returns <SAMP>true</SAMP> if for each pair of elements in the two ranges, the result of applying the binary predicate is true. In other words, <SAMP>equal()</SAMP> returns <SAMP>true</SAMP> if both of the following are true:</P>
	<UL>
	<LI><P CLASS="LIST">There are at least as many elements in the second range as in the first</P></LI>
	<LI><P CLASS="LIST">For every iterator <SAMP>i</SAMP> in the range <SAMP>[start1, finish1)</SAMP> the following corresponding conditions hold: </P></LI>
	<P CLASS="LIST"><SAMP>i == (start2 + (i - start1))</SAMP></P>
	<P CLASS="LIST">or</P>
	<P CLASS="LIST"><SAMP>binary_pred(i, (start2 + (i - start1))) == true</SAMP></P>
	</UL>
	<P>If one of these conditions is not true, <SAMP>equal()</SAMP> returns <SAMP>false</SAMP>.</P>
	<P>This algorithm assumes that all iterators in the range <SAMP>[start2, start2 + (finish1 - start1)]</SAMP> are dereferenceable.</P>
	<A NAME="sec5"><H3>Complexity</H3></A>
	<P><SAMP>equal()</SAMP> performs at most <SAMP>finish1 - start1</SAMP> comparisons or applications of the predicate.</P>
	<A NAME="sec6"><H3>Example</H3></A>

	<UL><PRE>//
	// equal.cpp
	//

	#include <algorithm> // equal
	#include <functional>
	#include <iostream>
	#include <vector>



	int main ()
	{
	// Typedef for convenience.
	typedef std::vector<int, std::allocator<int> > vector;

	typedef std::ostream_iterator <vector::value_type, char,
	std::char_traits<char> > os_iter;

	const vector::value_type a1[] = { 1, 2, 3, 4 };
	const vector::value_type a2[] = { 1, 2, 4, 3 };

	// Set up two vectors.
	const vector v1(a1, a1 + sizeof a1 / sizeof *a1);
	const vector v2(a2, a2 + sizeof a2 / sizeof *a2);

	// Check for equality.
	bool same = std::equal(v1.begin(), v1.end(),
	v2.begin());

	same = same && std::equal(v1.begin(), v1.end(),
	v2.begin(), std::equal_to<vector::value_type>());

	// Output the sequences.
	std::cout << "{ ";
	std::copy(v1.begin(), v1.end(), os_iter(std::cout, " "));

	std::cout << "} == { ";
	std::copy(v2.begin(), v2.end(), os_iter(std::cout, " "));

	// Output the result.
	std::cout << "} --> " << std::boolalpha
	<< same << std::endl;

	return 0;
	}


	Program Output
	</PRE></UL>
	<UL><PRE>{ 1 2 3 4 } == { 1 2 4 3 } --> false

	</PRE></UL>
	<A NAME="sec7"><H3>Standards Conformance</H3></A>
	<P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems --Programming Language C++, Section 25.1.8</I></P>

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