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 <H2>reverse_iterator</H2>
 <P><B>Library:</B>&nbsp;&nbsp;<A HREF="2-8.html">Iterators</A></P>

 <PRE><HR><B><I>Does not inherit</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">Interface</A></LI>
 <LI><A HREF="#sec6">Example</A></LI>
 <LI><A HREF="#sec7">Complexity</A></LI>
 <LI><A HREF="#sec8">See Also</A></LI>
 <LI><A HREF="#sec9">Standards Conformance</A></LI>
 </UL>
 <A NAME="sec1"><H3>Local Index</H3></A>
 No Entries
 <A NAME="sec2"><H3>Summary</H3></A>
 <P>An iterator adaptor that traverses a collection backwards.</P>
 <A NAME="sec3"><H3>Synopsis</H3></A>

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

 namespace std {
   template &lt;class Iterator&gt;
   class <B>reverse_iterator</B>;
 }
 </PRE>
 <A NAME="sec4"><H3>Description</H3></A>
 <P>The class template <B><I>reverse_iterator</I></B> adapts any random access iterator or <B><I>bidirectional_iterator</I></B> to facilitate the traversal of collections in the opposite direction. The fundamental relationship between a reverse iterator and its corresponding iterator <SAMP>i</SAMP> is established by the identity:</P>

 <UL><PRE>
 &amp;*(reverse_iterator(i)) == &amp;*(i - 1);
 </PRE></UL>
 <P>This mapping is necessary because, while an iterator past the end of a sequence is still valid but not dereferenceable, there might not be a valid iterator before its beginning.</P>
 <A NAME="sec5"><H3>Interface</H3></A>

 <UL><PRE>namespace std {

   template &lt;class Iterator&gt;
   class reverse_iterator
     : public iterator
        &lt;typename iterator_traits&lt;iterator&gt;::iterator_category,
        &lt;typename iterator_traits&lt;iterator&gt;::value_type,
        &lt;typename iterator_traits&lt;iterator&gt;::difference_type,
        &lt;typename iterator_traits&lt;iterator&gt;::pointer,
        &lt;typename iterator_traits&lt;iterator&gt;::reference&gt;
   {

     public:
       typedef Iterator iterator_type;

       reverse_iterator();
       explicit reverse_iterator(iterator_type);

       iterator_type base();

       reference operator*();

       reverse_iterator&amp; operator++();
       reverse_iterator  operator++(int);
       reverse_iterator&amp; operator--();
       reverse_iterator  operator--(int);

       reverse_iterator  operator+  (difference_type) const;
       reverse_iterator&amp; operator+= (difference_type);
       reverse_iterator operator-   (difference_type) const;
       reverse_iterator&amp; operator-= (difference_type);

       reference operator[] (difference_type) const;
   };

   // Nonmember Operators

   template &lt;class Iterator&gt;
   bool operator== (const reverse_iterator&lt;Iterator&gt;&amp;,
                    const reverse_iterator&lt;Iterator&gt;&amp;);

   template &lt;class Iterator&gt;
   bool operator!= (const reverse_iterator&lt;Iterator&gt;&amp;,
                    const reverse_iterator&lt;Iterator&gt;&amp;);

   template &lt;class Iterator&gt;
   bool operator&lt; (const reverse_iterator&lt;Iterator&gt;&amp;,
                   const reverse_iterator&lt;Iterator&gt;&amp;);

   template &lt;class Iterator&gt;
   bool operator&gt; (const reverse_iterator&lt;Iterator&gt;&amp;,
                   const reverse_iterator&lt;Iterator&gt;&amp;);

   template &lt;class Iterator&gt;
   bool operator&lt;= (const reverse_iterator&lt;Iterator&gt;&amp;,
                    const reverse_iterator&lt;Iterator&gt;&amp;);

   template &lt;class Iterator&gt;
   bool operator&gt;= (const reverse_iterator&lt;Iterator&gt;&amp;,
                    const reverse_iterator&lt;Iterator&gt;&amp;);

   template &lt;class Iterator&gt;
   typename reverse_iterator&lt;Iterator&gt;::difference_type
   operator- (const reverse_iterator&lt;Iterator&gt;&amp;,
              const reverse_iterator&lt;Iterator&gt;&amp;);

   template &lt;class Iterator&gt;
   reverse_iterator&lt;Iterator&gt;
   operator+ (
       typename reverse_iterator&lt;Iterator&gt;::difference_type,
       const reverse_iterator&lt;Iterator&gt;&amp;);
 }
 </PRE></UL>
 <A NAME="sec6"><H3>Example</H3></A>

 <UL><PRE>//
 //  rev_itr.cpp
 //

 #include &lt;iostream&gt;   // for cout, endl
 #include &lt;vector&gt;     // for vector


 int main ()
 {
     typedef std::vector&lt;int, std::allocator&lt;int&gt; &gt; Vector;

     // Initialize a vector using an array.
     const Vector::value_type arr[] = { 3, 4, 7, 8 };
     const Vector v (arr + 0, arr + sizeof arr / sizeof *arr);

     // Output the original vector.
     std::cout &lt;&lt; "Traversing vector with iterator: \n     ";
     for (Vector::const_iterator i = v.begin ();
          i != v.end (); ++i)
         std::cout &lt;&lt; *i &lt;&lt; " ";

     // Output the vector backwards.
     std::cout &lt;&lt; "\n\nSame vector, same loop, "
               &lt;&lt; "reverse_iterator: \n     ";
     for (Vector::const_reverse_iterator j (v.end ());
          j != Vector::const_reverse_iterator (v.begin ());
          ++j)
         std::cout &lt;&lt; *j &lt;&lt; " ";

     std::cout &lt;&lt; std::endl;

     return 0;
 }


 Program Output:
 </PRE></UL>
 <UL><PRE>Traversing vector with iterator:
      3 4 7 8

 Same vector, same loop, reverse_iterator:
      8 7 4 3
 </PRE></UL>
 <A NAME="sec7"><H3>Complexity</H3></A>
 <P>All iterator operations are required to take at most amortized constant time.</P>
 <A NAME="sec8"><H3>See Also</H3></A>
 <P><A HREF="iterators.html">Iterators</A></P>
 <A NAME="sec9"><H3>Standards Conformance</H3></A>
 <P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 24.4.1.1</I></P>

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	<TITLE>reverse_iterator</TITLE>
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	<A HREF="reverse-copy.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="rotate.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>reverse_iterator</H2>
	<P><B>Library:</B>  <A HREF="2-8.html">Iterators</A></P>

	<PRE><HR><B><I>Does not inherit</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">Interface</A></LI>
	<LI><A HREF="#sec6">Example</A></LI>
	<LI><A HREF="#sec7">Complexity</A></LI>
	<LI><A HREF="#sec8">See Also</A></LI>
	<LI><A HREF="#sec9">Standards Conformance</A></LI>
	</UL>
	<A NAME="sec1"><H3>Local Index</H3></A>
	No Entries
	<A NAME="sec2"><H3>Summary</H3></A>
	<P>An iterator adaptor that traverses a collection backwards.</P>
	<A NAME="sec3"><H3>Synopsis</H3></A>

	<PRE>#include <iterator>

	namespace std {
	template <class Iterator>
	class <B>reverse_iterator</B>;
	}
	</PRE>
	<A NAME="sec4"><H3>Description</H3></A>
	<P>The class template <B><I>reverse_iterator</I></B> adapts any random access iterator or <B><I>bidirectional_iterator</I></B> to facilitate the traversal of collections in the opposite direction. The fundamental relationship between a reverse iterator and its corresponding iterator <SAMP>i</SAMP> is established by the identity:</P>

	<UL><PRE>
	&(reverse_iterator(i)) == &(i - 1);
	</PRE></UL>
	<P>This mapping is necessary because, while an iterator past the end of a sequence is still valid but not dereferenceable, there might not be a valid iterator before its beginning.</P>
	<A NAME="sec5"><H3>Interface</H3></A>

	<UL><PRE>namespace std {

	template <class Iterator>
	class reverse_iterator
	: public iterator
	<typename iterator_traits<iterator>::iterator_category,
	<typename iterator_traits<iterator>::value_type,
	<typename iterator_traits<iterator>::difference_type,
	<typename iterator_traits<iterator>::pointer,
	<typename iterator_traits<iterator>::reference>
	{

	public:
	typedef Iterator iterator_type;

	reverse_iterator();
	explicit reverse_iterator(iterator_type);

	iterator_type base();

	reference operator*();

	reverse_iterator& operator++();
	reverse_iterator operator++(int);
	reverse_iterator& operator--();
	reverse_iterator operator--(int);

	reverse_iterator operator+ (difference_type) const;
	reverse_iterator& operator+= (difference_type);
	reverse_iterator operator- (difference_type) const;
	reverse_iterator& operator-= (difference_type);

	reference operator[] (difference_type) const;
	};

	// Nonmember Operators

	template <class Iterator>
	bool operator== (const reverse_iterator<Iterator>&,
	const reverse_iterator<Iterator>&);

	template <class Iterator>
	bool operator!= (const reverse_iterator<Iterator>&,
	const reverse_iterator<Iterator>&);

	template <class Iterator>
	bool operator< (const reverse_iterator<Iterator>&,
	const reverse_iterator<Iterator>&);

	template <class Iterator>
	bool operator> (const reverse_iterator<Iterator>&,
	const reverse_iterator<Iterator>&);

	template <class Iterator>
	bool operator<= (const reverse_iterator<Iterator>&,
	const reverse_iterator<Iterator>&);

	template <class Iterator>
	bool operator>= (const reverse_iterator<Iterator>&,
	const reverse_iterator<Iterator>&);

	template <class Iterator>
	typename reverse_iterator<Iterator>::difference_type
	operator- (const reverse_iterator<Iterator>&,
	const reverse_iterator<Iterator>&);

	template <class Iterator>
	reverse_iterator<Iterator>
	operator+ (
	typename reverse_iterator<Iterator>::difference_type,
	const reverse_iterator<Iterator>&);
	}
	</PRE></UL>
	<A NAME="sec6"><H3>Example</H3></A>

	<UL><PRE>//
	// rev_itr.cpp
	//

	#include <iostream> // for cout, endl
	#include <vector> // for vector


	int main ()
	{
	typedef std::vector<int, std::allocator<int> > Vector;

	// Initialize a vector using an array.
	const Vector::value_type arr[] = { 3, 4, 7, 8 };
	const Vector v (arr + 0, arr + sizeof arr / sizeof *arr);

	// Output the original vector.
	std::cout << "Traversing vector with iterator: \n ";
	for (Vector::const_iterator i = v.begin ();
	i != v.end (); ++i)
	std::cout << *i << " ";

	// Output the vector backwards.
	std::cout << "\n\nSame vector, same loop, "
	<< "reverse_iterator: \n ";
	for (Vector::const_reverse_iterator j (v.end ());
	j != Vector::const_reverse_iterator (v.begin ());
	++j)
	std::cout << *j << " ";

	std::cout << std::endl;

	return 0;
	}


	Program Output:
	</PRE></UL>
	<UL><PRE>Traversing vector with iterator:
	3 4 7 8

	Same vector, same loop, reverse_iterator:
	8 7 4 3
	</PRE></UL>
	<A NAME="sec7"><H3>Complexity</H3></A>
	<P>All iterator operations are required to take at most amortized constant time.</P>
	<A NAME="sec8"><H3>See Also</H3></A>
	<P><A HREF="iterators.html">Iterators</A></P>
	<A NAME="sec9"><H3>Standards Conformance</H3></A>
	<P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 24.4.1.1</I></P>

	<BR>
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