📄 distance.html
字号:
<HTML><!-- -- Copyright (c) 1996-1999 -- Silicon Graphics Computer Systems, Inc. -- -- Permission to use, copy, modify, distribute and sell this software -- and its documentation for any purpose is hereby granted without fee, -- provided that the above copyright notice appears in all copies and -- that both that copyright notice and this permission notice appear -- in supporting documentation. Silicon Graphics makes no -- representations about the suitability of this software for any -- purpose. It is provided "as is" without express or implied warranty. -- -- Copyright (c) 1994 -- Hewlett-Packard Company -- -- Permission to use, copy, modify, distribute and sell this software -- and its documentation for any purpose is hereby granted without fee, -- provided that the above copyright notice appears in all copies and -- that both that copyright notice and this permission notice appear -- in supporting documentation. Hewlett-Packard Company makes no -- representations about the suitability of this software for any -- purpose. It is provided "as is" without express or implied warranty. -- --><Head><Title>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>distance</H1><Table CellPadding=0 CellSpacing=0 width=100%><TR><TD Align=left><Img src = "algorithms.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD><TD Align=right><Img src = "function.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD></TR><TR><TD Align=left><Img src = "iterators.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD><TD Align=right></TD></TR><TR><TD Align=left VAlign=top><b>Categories</b>: algorithms, iterators</TD><TD Align=right VAlign=top><b>Component type</b>: function</TD></TR></Table><h3>Prototype</h3><tt>Distance</tt> is an overloaded name; there are actually two <tt>distance</tt>functions.<pre>template <class InputIterator>inline <A href="iterator_traits.html">iterator_traits</A><InputIterator>::difference_typedistance(InputIterator first, InputIterator last);template <class <A href="InputIterator.html">InputIterator</A>, class Distance>void distance(InputIterator first, InputIterator last, Distance& n);</pre> <h3>Description</h3>Finds the distance between <tt>first</tt> and <tt>last</tt>, <i>i.e.</i> the number oftimes that <tt>first</tt> must be incremented until it is equal to<tt>last</tt>. <A href="#1">[1]</A> The first version of <tt>distance</tt>, which takes two arguments,simply returns that distance; the second version, which takesthree arguments and which has a return type of <tt>void</tt>, increments<tt>n</tt> by that distance.<P>The second version of <tt>distance</tt> was the one defined in the originalSTL, and the first version is the one defined in the draft C++ standard; the definition was changed because theolder interface was clumsy and error-prone. The older interfacerequired the use of a temporary variable, and it has semanticsthat are somewhat nonintuitive: it increments <tt>n</tt> by the distancefrom <tt>first</tt> to <tt>last</tt>, rather than storing that distance in <tt>n</tt>. <A href="#2">[2]</A><P>Both interfaces are currently supported <A href="#3">[3]</A>, forreasons of backward compatibility, but eventually the olderversion will be removed.<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>.<h3>Requirements on types</h3>For the first version:<UL><LI><tt>InputIterator</tt> is a model of <A href="InputIterator.html">Input Iterator</A>.</UL>For the second version:<UL><LI><tt>InputIterator</tt> is a model of <A href="InputIterator.html">Input Iterator</A>.<LI><tt>Distance</tt> is an integral type that is able to represent a distance between iterators of type <tt>InputIterator</tt>.</UL><h3>Preconditions</h3><UL><LI><tt>[first, last)</tt> is a <i>valid range</i>, as defined in the <A href="InputIterator.html">Input Iterator</A> requirements.</UL><h3>Complexity</h3>Constant time if <tt>InputIterator</tt> is a model of <A href="RandomAccessIterator.html">random access iterator</A>, otherwise linear time.<h3>Example</h3><pre>int main() { <A href="List.html">list</A><int> L; L.push_back(0); L.push_back(1); assert(distance(L.begin(), L.end()) == L.size());}</pre><h3>Notes</h3><P><A name="1">[1]</A>This is the reason that <tt>distance</tt> is not defined for<A href="OutputIterator.html">output iterators</A>: it is impossible to compare two <A href="OutputIterator.html">output iterators</A>for equality.<P><A name="2">[2]</A>Forgetting to initialize <tt>n</tt> to 0 is a common mistake.<P><A name="3">[3]</A>The new <tt>distance</tt> interface uses the <tt><A href="iterator_traits.html">iterator_traits</A></tt> class, whichrelies on a C++ feature known as <i>partial specialization</i>. Many oftoday's compilers don't implement the complete standard; inparticular, many compilers do not support partial specialization. Ifyour compiler does not support partial specialization, then you willnot be able to use the newer version of <tt>distance</tt>, or any other STLcomponents that involve <tt><A href="iterator_traits.html">iterator_traits</A></tt>.<h3>See also</h3><tt><A href="distance_type.html">distance_type</A></tt>, <tt><A href="advance.html">advance</A></tt>, <A href="InputIterator.html">Input iterator</A>, <A href="RandomAccessIterator.html">Random access iterator</A>, <A href="iterator_tags.html">Iterator tags</A>,<tt><A href="iterator_traits.html">iterator_traits</A></tt>, <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. All rights reserved.</TD> <TD ALIGN="CENTER" CLASS="footer"> | </TD> <TD ALIGN="LEFT" CLASS="footer"><A HREF="/company_info/trademarks/" TARGET="_top">Trademark Information</A></TD> </TR></TABLE><!-- Footer Ends --><!-- end footer --><P></BODY></HTML> ⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -