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It is provided "as is" without express or implied warranty. -- --><Head><Title>forward_iterator<T, Distance></Title><!-- Generated by htmldoc --></HEAD><BODY BGCOLOR="#ffffff" LINK="#0000ee" TEXT="#000000" VLINK="#551a8b" ALINK="#ff0000"> <IMG SRC="CorpID.gif" ALT="SGI" HEIGHT="43" WIDTH="151"> <!--end header--><BR Clear><H1>forward_iterator<T, 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 = "39" ></TD></TR><TR><TD Align=left VAlign=top><b>Category</b>: iterators</TD><TD Align=right VAlign=top><b>Component type</b>: type</TD></TR></Table><h3>Description</h3><tt>Forward_iterator</tt> is an iterator base class: it is intended that aniterator that is a model of <A href="ForwardIterator.html">Forward Iterator</A>, and whose value typeand distance type are <tt>T</tt> and <tt>Distance</tt>, may be defined by inheriting from<tt>forward_iterator<T, Distance></tt> <A href="#1">[1]</A>. <tt>Forward_iterator</tt> is entirely empty: it has nomember functions, member variables, or nested types. It exists solelyto simplify the definition of the 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>.<h3>Example</h3><pre>class my_forward_iterator : public forward_iterator<double> { ...};</pre>This declares <tt>my_forward_iterator</tt> to be a <A href="ForwardIterator.html">Forward Iterator</A> whosevalue type is <tt>double</tt> and whose distance type is <tt>ptrdiff_t</tt>. If <tt>Iter</tt> is an object of class <tt>my_forward_iterator</tt>, then<tt><A href="iterator_category.html">iterator_category</A>(Iter)</tt> will return <tt><A href="forward_iterator_tag.html">forward_iterator_tag</A>()</tt>,<tt><A href="value_type.html">value_type</A>(Iter)</tt> will return <tt>(double*) 0</tt>, and <tt><A href="distance_type.html">distance_type</A>(Iter)</tt>will return <tt>(ptrdiff_t*) 0</tt>.<h3>Definition</h3>Defined in the standard header <A href="iterator">iterator</A>, and in thenonstandard backward-compatibility header <A href="iterator.h">iterator.h</A>.This class is no longer part of the C++ standard, althoughit was present in early drafts of the standard. It is retainedin 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>T</tt></TD><TD VAlign=top>The iterator's value type</TD><TD VAlign=top> </TD></TR><TR><TD VAlign=top><tt>Distance</tt></TD><TD VAlign=top>The iterator's distance type</TD><TD VAlign=top><tt>ptrdiff_t</tt></TD></tr></table><h3>Model of</h3><A href="Assignable.html">Assignable</A><h3>Public base classes</h3>None<h3>Type requirements</h3>The distance type must be a signed integral type.<h3>Public base classes</h3>None.<h3>Members</h3>None.<h3>New Members</h3>None.<h3>Notes</h3><P><A name="1">[1]</A>It is not required that a <A href="ForwardIterator.html">Forward Iterator</A> inherit from thebase <tt>forward_iterator</tt>. It is, however, required that the 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>be defined for every <A href="ForwardIterator.html">Forward Iterator</A>. (Or, if you are using the <tt><A href="iterator_traits.html">iterator_traits</A></tt> mechanism, that<tt>iterator_traits</tt> is properly specialized for every <A href="ForwardIterator.html">Forward Iterator</A>.)Since those functions are defined for the base <tt>forward_iterator</tt>, theeasiest way to ensure that are defined for a new type is to derivethat class from <tt>forward_iterator</tt> and rely on the derived-to-basestandard conversion of function arguments.<h3>See also</h3>The <A href="iterator_tags.html">Iterator Tags</A> overview, <tt><A href="iterator_traits.html">iterator_traits</A></tt>,<tt><A href="iterator_category.html">iterator_category</A></tt>,<tt><A href="value_type.html">value_type</A></tt>, <tt><A href="distance_type.html">distance_type</A></tt>,<tt><A href="input_iterator.html">input_iterator</A></tt>, <tt><A href="output_iterator.html">output_iterator</A></tt>,<tt><A href="bidirectional_iterator.html">bidirectional_iterator</A></tt>, <tt><A href="random_access_iterator.html">random_access_iterator</A></tt><!--start footer--> <HR SIZE="6"><A href="http://www.sgi.com/"><IMG SRC="surf.gif" HEIGHT="54" WIDTH="54" ALT="[Silicon Surf]"></A><A HREF="index.html"><IMG SRC="stl_home.gif" HEIGHT="54" WIDTH="54" ALT="[STL Home]"></A><BR><FONT SIZE="-2"><A href="http://www.sgi.com/Misc/sgi_info.html" TARGET="_top">Copyright © 1999 Silicon Graphics, Inc.</A> All Rights Reserved.</FONT><FONT SIZE="-3"><a href="http://www.sgi.com/Misc/external.list.html" TARGET="_top">TrademarkInformation</A></FONT><P></BODY></HTML> ⌨️ 快捷键说明
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