doc/stdlibref/distance.html - stdcxx - Git at Google

 <!--
     Licensed to the Apache Software  Foundation (ASF) under one or more
     contributor  license agreements.  See  the NOTICE  file distributed
     with  this  work  for  additional information  regarding  copyright
     ownership.   The ASF  licenses this  file to  you under  the Apache
     License, Version  2.0 (the  License); you may  not use  this file
     except in  compliance with the License.   You may obtain  a copy of
     the License at

     http://www.apache.org/licenses/LICENSE-2.0

     Unless required by applicable law or agreed to in writing, software
     distributed under the  License is distributed on an  "AS IS" BASIS,
     WITHOUT  WARRANTIES OR CONDITIONS  OF ANY  KIND, either  express or
     implied.   See  the License  for  the  specific language  governing
     permissions and limitations under the License.

     Copyright 1999-2007 Rogue Wave Software, Inc.
 -->

 <HTML>
 <HEAD>
 <TITLE>distance()</TITLE>
 <LINK REL=StyleSheet HREF="../rw.css" TYPE="text/css" TITLE="Apache stdcxx Stylesheet"></HEAD>
 <BODY BGCOLOR=#FFFFFF>
 <A HREF="deque.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="divides.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>distance()</H2>
 <P><B>Library:</B>&nbsp;&nbsp;<A HREF="2-8.html">Iterators</A></P>

 <PRE><HR><B><I>Function</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">Example</A></LI>
 <LI><A HREF="#sec6">Warnings</A></LI>
 <LI><A HREF="#sec7">See Also</A></LI>
 <LI><A HREF="#sec8">Standards Conformance</A></LI>
 </UL>
 <A NAME="sec1"><H3>Local Index</H3></A>
 No Entries
 <A NAME="sec2"><H3>Summary</H3></A>
 <P>A function that computes the distance between two iterators</P>
 <A NAME="sec3"><H3>Synopsis</H3></A>

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

 namespace std {
   template &lt;class ForwardIterator&gt;
   iterator_traits&lt;ForwardIterator&gt;::difference_type
   distance(ForwardIterator start,
            ForwardIterator finish);

   template &lt;class ForwardIterator, class Distance&gt;
   void distance(ForwardIterator start,
                 ForwardIterator finish,
                 Distance&amp; n);
 }
 </PRE>
 <A NAME="sec4"><H3>Description</H3></A>
 <P>The <SAMP>distance()</SAMP> function template computes the distance between two iterators. The first version returns that value, while the second version increments <SAMP>n</SAMP> by that value. The last iterator must be reachable from the first iterator. </P>
 <P>Note that the second version of this function is obsolete. It is included for backward compatibility and to accommodate compilers that do not support partial specialization. The first version of the function is not available with compilers that do not support partial specialization, since it depends on <B><I><A HREF="iterator-traits.html">iterator_traits</A></I></B>, which itself depends on that particular language feature.</P>
 <A NAME="sec5"><H3>Example</H3></A>

 <UL><PRE>//
 // distance.cpp
 //

 #include &lt;iterator&gt;
 #include &lt;iostream&gt;
 #include &lt;vector&gt;


 int main ()
 {
     // Typedefs for convenience.
     typedef std::vector&lt;int, std::allocator&lt;int&gt; &gt; vector;

     typedef std::ostream_iterator&lt;vector::value_type, char,
                               std::char_traits&lt;char&gt; &gt; os_iter;

     // Initialize a vector using an array.
     const vector::value_type arr [] = { 3, 4, 5, 6, 7, 8 };
     const vector v (arr + 0, arr + sizeof arr/ sizeof *arr);

     // Declare a vector iterator, s.b. a ForwardIterator.
     vector::const_iterator it = v.begin () + 3;

     // Output the original vector.
     std::cout &lt;&lt; "For the vector: ";
     std::copy (v.begin (), v.end (), os_iter (std::cout, " "));
     std::cout &lt;&lt; std::endl;

     std::cout &lt;&lt; "\nWhen the iterator is initialized "
               &lt;&lt; "to point to " &lt;&lt; *it &lt;&lt; std::endl;

     // Compute the distance of it from the first element.
     vector::difference_type dist = 0;
     std::distance (v.begin (), it, dist);

     std::cout &lt;&lt; "The distance between the beginning and "
               &lt;&lt; *it &lt;&lt; " is " &lt;&lt; dist &lt;&lt; std::endl;

     return 0;
 }


 Program Output:
 </PRE></UL>
 <UL><PRE>For the vector: 3 4 5 6 7 8

 When the iterator is initialized to point to 6
 The distance between the beginning and 6 is 3
 </PRE></UL>
 <A NAME="sec6"><H3>Warnings</H3></A>
 <P>If your compiler does not support partial specialization, you can't use the version of <SAMP>distance()</SAMP> that returns the distance. Instead, you must use the version that increments a reference parameter.</P>
 <A NAME="sec7"><H3>See Also</H3></A>
 <P><A HREF="sequences.html">Sequences</A>, <A HREF="randomaccessiterators.html">Random Access Iterators</A></P>
 <A NAME="sec8"><H3>Standards Conformance</H3></A>
 <P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 24.3.4</I></P>

 <BR>
 <HR>
 <A HREF="deque.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="divides.html"><IMG SRC="images/bnext.gif" WIDTH=20 HEIGHT=21 ALT="Next file" BORDER=O></A>

 <!-- Google Analytics tracking code -->
 <script src="http://www.google-analytics.com/urchin.js" type="text/javascript">
 </script>
 <script type="text/javascript">
     _uacct = "UA-1775151-1";
     urchinTracker();
 </script>
 <!-- end of Google Analytics tracking code -->

 </BODY>
 </HTML>
	<!--
	Licensed to the Apache Software Foundation (ASF) under one or more
	contributor license agreements. See the NOTICE file distributed
	with this work for additional information regarding copyright
	ownership. The ASF licenses this file to you under the Apache
	License, Version 2.0 (the License); you may not use this file
	except in compliance with the License. You may obtain a copy of
	the License at

	http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
	implied. See the License for the specific language governing
	permissions and limitations under the License.

	Copyright 1999-2007 Rogue Wave Software, Inc.
	-->

	<HTML>
	<HEAD>
	<TITLE>distance()</TITLE>
	<LINK REL=StyleSheet HREF="../rw.css" TYPE="text/css" TITLE="Apache stdcxx Stylesheet"></HEAD>
	<BODY BGCOLOR=#FFFFFF>
	<A HREF="deque.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="divides.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>distance()</H2>
	<P><B>Library:</B>  <A HREF="2-8.html">Iterators</A></P>

	<PRE><HR><B><I>Function</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">Example</A></LI>
	<LI><A HREF="#sec6">Warnings</A></LI>
	<LI><A HREF="#sec7">See Also</A></LI>
	<LI><A HREF="#sec8">Standards Conformance</A></LI>
	</UL>
	<A NAME="sec1"><H3>Local Index</H3></A>
	No Entries
	<A NAME="sec2"><H3>Summary</H3></A>
	<P>A function that computes the distance between two iterators</P>
	<A NAME="sec3"><H3>Synopsis</H3></A>

	<PRE>#include <iterator>

	namespace std {
	template <class ForwardIterator>
	iterator_traits<ForwardIterator>::difference_type
	distance(ForwardIterator start,
	ForwardIterator finish);

	template <class ForwardIterator, class Distance>
	void distance(ForwardIterator start,
	ForwardIterator finish,
	Distance& n);
	}
	</PRE>
	<A NAME="sec4"><H3>Description</H3></A>
	<P>The <SAMP>distance()</SAMP> function template computes the distance between two iterators. The first version returns that value, while the second version increments <SAMP>n</SAMP> by that value. The last iterator must be reachable from the first iterator. </P>
	<P>Note that the second version of this function is obsolete. It is included for backward compatibility and to accommodate compilers that do not support partial specialization. The first version of the function is not available with compilers that do not support partial specialization, since it depends on <B><I><A HREF="iterator-traits.html">iterator_traits</A></I></B>, which itself depends on that particular language feature.</P>
	<A NAME="sec5"><H3>Example</H3></A>

	<UL><PRE>//
	// distance.cpp
	//

	#include <iterator>
	#include <iostream>
	#include <vector>



	int main ()
	{
	// Typedefs for convenience.
	typedef std::vector<int, std::allocator<int> > vector;

	typedef std::ostream_iterator<vector::value_type, char,
	std::char_traits<char> > os_iter;

	// Initialize a vector using an array.
	const vector::value_type arr [] = { 3, 4, 5, 6, 7, 8 };
	const vector v (arr + 0, arr + sizeof arr/ sizeof *arr);

	// Declare a vector iterator, s.b. a ForwardIterator.
	vector::const_iterator it = v.begin () + 3;

	// Output the original vector.
	std::cout << "For the vector: ";
	std::copy (v.begin (), v.end (), os_iter (std::cout, " "));
	std::cout << std::endl;

	std::cout << "\nWhen the iterator is initialized "
	<< "to point to " << *it << std::endl;

	// Compute the distance of it from the first element.
	vector::difference_type dist = 0;
	std::distance (v.begin (), it, dist);

	std::cout << "The distance between the beginning and "
	<< *it << " is " << dist << std::endl;

	return 0;
	}


	Program Output:
	</PRE></UL>
	<UL><PRE>For the vector: 3 4 5 6 7 8

	When the iterator is initialized to point to 6
	The distance between the beginning and 6 is 3
	</PRE></UL>
	<A NAME="sec6"><H3>Warnings</H3></A>
	<P>If your compiler does not support partial specialization, you can't use the version of <SAMP>distance()</SAMP> that returns the distance. Instead, you must use the version that increments a reference parameter.</P>
	<A NAME="sec7"><H3>See Also</H3></A>
	<P><A HREF="sequences.html">Sequences</A>, <A HREF="randomaccessiterators.html">Random Access Iterators</A></P>
	<A NAME="sec8"><H3>Standards Conformance</H3></A>
	<P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 24.3.4</I></P>

	<BR>
	<HR>
	<A HREF="deque.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="divides.html"><IMG SRC="images/bnext.gif" WIDTH=20 HEIGHT=21 ALT="Next file" BORDER=O></A>

	<!-- Google Analytics tracking code -->
	<script src="http://www.google-analytics.com/urchin.js" type="text/javascript">
	</script>
	<script type="text/javascript">
	_uacct = "UA-1775151-1";
	urchinTracker();
	</script>
	<!-- end of Google Analytics tracking code -->

	</BODY>
	</HTML>