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It is provided "as is" without express or implied warranty. -- --><Head><Title>reverse_bidirectional_iterator<BidirectionalIterator, T, Reference, Distance></Title><!-- Generated by htmldoc --></HEAD><BODY TEXT="#000000" LINK="#006600" ALINK="#003300" VLINK="#7C7F87" BGCOLOR="#FFFFFF"><A HREF="/"><IMG SRC="/images/common/sgilogo_small.gif" ALT="SGI Logo" WIDTH="80" HEIGHT="72" BORDER="0"></A><P><!--end header--><BR Clear><H1>reverse_bidirectional_iterator<BidirectionalIterator, T, Reference, Distance></H1><Table CellPadding=0 CellSpacing=0 width=100%><TR><TD Align=left><Img src = "iterators.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD><TD Align=right><Img src = "type.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD></TR><TR><TD Align=left><Img src = "adaptors.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD><TD Align=right></TD></TR><TR><TD Align=left VAlign=top><b>Categories</b>: iterators, adaptors</TD><TD Align=right VAlign=top><b>Component type</b>: type</TD></TR></Table><h3>Description</h3><tt>Reverse_bidirectional_iterator</tt> is an iterator adaptor that enables backwards traversal of a range. <tt>Operator++</tt> applied to an object of class <tt>reverse_bidirectional_iterator<<A href="BidirectionalIterator.html">BidirectionalIterator</A>></tt> means the same thing as<tt>operator--</tt> applied to an object of class <tt><A href="BidirectionalIterator.html">BidirectionalIterator</A></tt>.There are two different reverse iterator adaptors: the class<tt>reverse_bidirectional_iterator</tt>has a template argument that is a <A href="BidirectionalIterator.html">Bidirectional Iterator</A>,and the class <tt><A href="ReverseIterator.html">reverse_iterator</A></tt> has a template argument that is a<A href="RandomAccessIterator.html">Random Access Iterator</A>. <A href="#1">[1]</A><h3>Example</h3><pre>template <class T>void forw(const <A href="List.html">list</A><T>& L){ list<T>::iterator first = L.begin(); list<T>::iterator last = L.end(); while (first != last) cout << *first++ << endl;} template <class T>void rev(const <A href="List.html">list</A><T>& L){ typedef reverse_bidirectional_iterator<list<T>::iterator, T, list<T>::reference_type, list<T>::difference_type> reverse_iterator; <A href="#2">[2]</A> reverse_iterator rfirst(L.end()); reverse_iterator rlast(L.begin()); while (rfirst != rlast) cout << *rfirst++ << endl;} </pre><P>In the function <tt>forw</tt>, the elements are printed in the order<tt>*first</tt>, <tt>*(first+1)</tt>, ..., <tt>*(last-1)</tt>. In the function <tt>rev</tt>, they are printed in the order <tt>*(last - 1)</tt>, <tt>*(last-2)</tt>, ...,<tt>*first</tt>. <A href="#3">[3]</A><h3>Definition</h3>Defined in the standard header <A href="iterator">iterator</A>, and in the nonstandardbackward-compatibility header <A href="iterator.h">iterator.h</A>. This class is no longerpart of the C++ standard, but it was present in early drafts, andit is retained in this implementation for backward compatibility.<h3>Template parameters</h3><Table border><TR><TH>Parameter</TH><TH>Description</TH><TH>Default</TH></TR><TR><TD VAlign=top><tt>BidirectionalIterator</tt></TD><TD VAlign=top>The base iterator class. Incrementing an object of class <tt>reverse_bidirectional_iterator<BidirectionalIterator></tt> corresponds to decrementing an object of class <tt>BidirectionalIterator</tt>.</TD><TD VAlign=top> </TD></TR><TR><TD VAlign=top><tt>T</tt></TD><TD VAlign=top>The reverse iterator's value type. This should always be the same as the base iterator's value type.</TD><TD VAlign=top> </TD></TR><TR><TD VAlign=top><tt>Reference</tt></TD><TD VAlign=top>The reverse iterator's reference type. This should always be the same as the base iterator's reference type.</TD><TD VAlign=top><tt>T&</tt></TD></TR><TR><TD VAlign=top><tt>Distance</tt></TD><TD VAlign=top>The reverse iterator's distance type. This should always be the same as the base iterator's distance type.</TD><TD VAlign=top><tt>ptrdiff_t</tt></TD></tr></table><h3>Model of</h3><A href="BidirectionalIterator.html">Bidirectional Iterator</A>.<h3>Type requirements</h3>The base iterator type (that is, the template parameter <tt>BidirectionalIterator</tt>)must be a <tt><A href="BidirectionalIterator.html">Bidirectional Iterator</A></tt>. The <tt>reverse_bidirectional_iterator</tt>'s value type, reference type, and distance type (that is, the template parameters<tt>T</tt>, <tt>Reference</tt>, and <tt>Distance</tt>, respectively) must be the same as thebase iterator's value type, reference type, and distance type.<h3>Public base classes</h3>None.<h3>Members</h3><Table border><TR><TH>Member</TH><TH>Where defined</TH><TH>Description</TH></TR><TR><TD VAlign=top><tt>self</tt></TD><TD VAlign=top><tt>reverse_bidirectional_iterator</tt></TD><TD VAlign=top>See below</TD></TR><TR><TD VAlign=top><tt>reverse_bidirectional_iterator()</tt></TD><TD VAlign=top> <A href="trivial.html">Trivial Iterator</A></TD><TD VAlign=top>The default constructor</TD></TR><TR><TD VAlign=top><tt>reverse_bidirectional_iterator(const reverse_bidirectional_iterator& x)</tt></TD><TD VAlign=top> <A href="trivial.html">Trivial Iterator</A></TD><TD VAlign=top>The copy constructor</TD></TR><TR><TD VAlign=top><tt>reverse_bidirectional_iterator& operator=(const reverse_bidirectional_iterator& x)</tt></TD><TD VAlign=top> <A href="trivial.html">Trivial Iterator</A></TD><TD VAlign=top>The assignment operator</TD></TR><TR><TD VAlign=top><tt>reverse_bidirectional_iterator(BidirectionalIterator x)</tt></TD><TD VAlign=top><tt>reverse_bidirectional_iterator</tt></TD><TD VAlign=top>See below.</TD></TR><TR><TD VAlign=top><tt>BidirectionalIterator base()</tt></TD><TD VAlign=top><tt>reverse_bidirectional_iterator</tt></TD><TD VAlign=top>See below.</TD></TR><TR><TD VAlign=top><tt>Reference operator*() const</tt></TD><TD VAlign=top> <A href="trivial.html">Trivial Iterator</A></TD><TD VAlign=top>The dereference operator</TD></TR><TR><TD VAlign=top><tt>reverse_bidirectional_iterator& operator++()</tt></TD><TD VAlign=top> <A href="ForwardIterator.html">Forward Iterator</A></TD><TD VAlign=top>Preincrement</TD></TR><TR><TD VAlign=top><tt>reverse_bidirectional_iterator operator++(int)</tt></TD><TD VAlign=top> <A href="ForwardIterator.html">Forward Iterator</A></TD><TD VAlign=top>Postincrement</TD></TR><TR><TD VAlign=top><tt>reverse_bidirectional_iterator& operator--()</tt></TD><TD VAlign=top> <A href="BidirectionalIterator.html">Bidirectional Iterator</A></TD><TD VAlign=top>Predecrement</TD></TR><TR><TD VAlign=top><tt>reverse_bidirectional_iterator operator--(int)</tt></TD><TD VAlign=top> <A href="BidirectionalIterator.html">Bidirectional Iterator</A></TD><TD VAlign=top>Postdecrement</TD></TR><TR><TD VAlign=top><tt>bool operator==(const reverse_bidirectional_iterator&, const reverse_bidirectional_iterator&)</tt></TD><TD VAlign=top> <A href="trivial.html">Trivial Iterator</A></TD><TD VAlign=top>Compares two iterators for equality. This is a global function, not a member function.</TD></TR><TR><TD VAlign=top><tt>bidirectional_iterator_tag iterator_category(const reverse_bidirectional_iterator&)</tt></TD><TD VAlign=top> <A href="iterator_tags.html">Iterator tags</A></TD><TD VAlign=top>Returns the iterator's category. This is a global function, not a member function.</TD></TR><TR><TD VAlign=top><tt>T* value_type(const reverse_bidirectional_iterator&)</tt></TD><TD VAlign=top> <A href="iterator_tags.html">Iterator tags</A></TD><TD VAlign=top>Returns the iterator's value type. This is a global function, not a member function.</TD></TR><TR><TD VAlign=top><tt>Distance* distance_type(const reverse_bidirectional_iterator&)</tt></TD><TD VAlign=top> <A href="iterator_tags.html">Iterator tags</A></TD><TD VAlign=top>Returns the iterator's distance type. This is a global function, not a member function.</TD></tr></table><h3>New members</h3>These members are not defined in the <A href="BidirectionalIterator.html">Bidirectional Iterator</A> requirements,but are specific to <tt>reverse_bidirectional_iterator</tt>.<Table border><TR><TH>Member</TH><TH>Description</TH></TR><TR><TD VAlign=top><tt>self</tt></TD><TD VAlign=top>A typedef for <tt>reverse_bidirectional_iterator<<A href="BidirectionalIterator.html">BidirectionalIterator</A>, T, Reference, Distance></tt>. </TD></TR><TR><TD VAlign=top><tt><A href="BidirectionalIterator.html">BidirectionalIterator</A> base()</tt></TD><TD VAlign=top>Returns the current value of the <tt>reverse_bidirectional_iterator</tt>'s base iterator. If <tt>ri</tt> is a reverse iterator and <tt>i</tt> is any iterator, the two fundamental identities of reverse iterators can be written as <tt>reverse_bidirectional_iterator(i).base() == i</tt> and <tt>&*ri == &*(ri.base() - 1)</tt>.</TD></TR><TR><TD VAlign=top><tt>reverse_bidirectional_iterator(<A href="BidirectionalIterator.html">BidirectionalIterator</A> i)</tt></TD><TD VAlign=top>Constructs a <tt>reverse_bidirectional_iterator</tt> whose base iterator is <tt>i</tt>.</TD></tr></table><h3>Notes</h3><P><A name="1">[1]</A>There isn't really any good reason to have two separate classes:this separation is purely because of a technical limitation in some oftoday's C++ compilers. If the two classes were combined into one, then therewould be no way to declare the return types of the <A href="iterator_tags.html">iterator tag</A>functions <tt><A href="iterator_category.html">iterator_category</A></tt>, <tt><A href="distance_type.html">distance_type</A></tt> and<tt><A href="value_type.html">value_type</A></tt> correctly. The <i>iterator traits</i>class solves this problem: it addresses the same issues as the iterator tagfunctions, but in a cleaner and more flexible manner. Iteratortraits, however, rely on <i>partial specialization</i>, and manyC++ compilers do not yet implement partial specialization.Once compilers that support partial specialization become more common,these two different reverse iterator classes will be combined into a single class.<P><A name="2">[2]</A>The declarations for <tt>rfirst</tt> and <tt>rlast</tt> are written in thisclumsy form simply as an illustration of how to declare a<tt>reverse_bidirectional_iterator</tt>. <tt><A href="List.html">List</A></tt> is a <A href="ReversibleContainer.html">Reversible Container</A>, so it provides a typedef for the appropriateinstantiation of <tt>reverse_bidirectional_iterator</tt>. The usual way ofdeclaring these variables is much simpler: <pre> list<T>::reverse_bidirectional_iterator rfirst = rbegin(); list<T>::reverse_bidirectional_iterator rlast = rend(); </pre><P><A name="3">[3]</A>Note the implications of this remark. The variable <tt>rfirst</tt> isinitialized as <tt>reverse_bidirectional_iterator<...> rfirst(V.end());</tt>. The valueobtained when it is dereferenced, however, is <tt>*(V.end() - 1)</tt>. Thisis a general property: the fundamental identity of reverse iteratorsis <tt>&*(reverse_bidirectional_iterator(i)) == &*(i - 1)</tt>. This code sample shows whythis identity is important: if <tt>[f, l)</tt> is a valid range, then itallows <tt>[reverse_bidirectional_iterator(l), reverse_bidirectional_iterator(f))</tt> to be a validrange as well. Note that the iterator <tt>l</tt> is not part of the range,but it is required to be dereferenceable or past-the-end. There is norequirement that any such iterator precedes <tt>f</tt>.<h3>See also</h3><A href="ReversibleContainer.html">Reversible Container</A>, <A href="ReverseIterator.html">reverse_iterator</A>,<A href="BidirectionalIterator.html">Bidirectional Iterator</A>, <A href="iterator_tags.html">iterator tags</A>, <A href="Iterators.html">Iterator overview</A><!-- start footer --><!-- Footer Begins --><STYLE TYPE="text/css"><!--TD.footer, TD.footer A{ font-family: Arial, helvetica, sans-serif; font-size: 8pt;}A.home {font-family: Arial, helvetica, sans-serif;}--></STYLE><P><A CLASS="home" HREF="index.html">STL Home</A><P><TABLE WIDTH="600" CELLPADDING="0" CELLPADDING="0" BORDER="0"> <TR> <TD ALIGN="RIGHT" CLASS="footer"><A HREF="/company_info/terms.html" TARGET="_top">terms of use</A> | <A HREF="/company_info/privacy.html" TARGET="_top">privacy policy</A></TD> <TD ALIGN="CENTER" CLASS="footer"> | </TD> <TD ALIGN="LEFT" CLASS="footer"><A HREF="/cgi-bin/feedback/" TARGET="_top">contact us</A></TD> </TR><TR> <TD ALIGN="RIGHT" CLASS="footer">Copyright © 1993-2003 Silicon Graphics, Inc. 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