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| <TITLE>reverse_iterator</TITLE> |
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| <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> |
| |
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