1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Function template distance()</title> 5<link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../index.html" title="Chapter 1. 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src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../algorithms.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="next_prior.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h3 class="title"> 27<a name="iterator.algorithms.distance"></a><a class="link" href="distance.html" title="Function template distance()">Function template <code class="computeroutput"><span class="identifier">distance</span><span class="special">()</span></code></a> 28</h3></div></div></div> 29<p> 30 The <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">iterators</span><span class="special">::</span><span class="identifier">distance</span></code> function template is an adapted 31 version of <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">distance</span></code> for the Boost iterator <a class="link" href="../concepts/traversal.html" title="Traversal">traversal 32 concepts</a>. 33 </p> 34<h5> 35<a name="iterator.algorithms.distance.h0"></a> 36 <span class="phrase"><a name="iterator.algorithms.distance.header"></a></span><a class="link" href="distance.html#iterator.algorithms.distance.header">Header</a> 37 </h5> 38<pre class="programlisting"><span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">iterator</span><span class="special">/</span><span class="identifier">distance</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 39</pre> 40<h5> 41<a name="iterator.algorithms.distance.h1"></a> 42 <span class="phrase"><a name="iterator.algorithms.distance.synopsis"></a></span><a class="link" href="distance.html#iterator.algorithms.distance.synopsis">Synopsis</a> 43 </h5> 44<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Iterator</span><span class="special">></span> 45<span class="keyword">constexpr</span> <span class="keyword">typename</span> <span class="identifier">iterator_difference</span><span class="special"><</span><span class="identifier">Iterator</span><span class="special">>::</span><span class="identifier">type</span> 46<span class="identifier">distance</span><span class="special">(</span><span class="identifier">Iterator</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">Iterator</span> <span class="identifier">last</span><span class="special">);</span> 47</pre> 48<h5> 49<a name="iterator.algorithms.distance.h2"></a> 50 <span class="phrase"><a name="iterator.algorithms.distance.description"></a></span><a class="link" href="distance.html#iterator.algorithms.distance.description">Description</a> 51 </h5> 52<p> 53 Computes the (signed) distance from <code class="computeroutput"><span class="identifier">first</span></code> 54 to <code class="computeroutput"><span class="identifier">last</span></code>. 55 </p> 56<h5> 57<a name="iterator.algorithms.distance.h3"></a> 58 <span class="phrase"><a name="iterator.algorithms.distance.requirements"></a></span><a class="link" href="distance.html#iterator.algorithms.distance.requirements">Requirements</a> 59 </h5> 60<p> 61 <code class="computeroutput"><span class="identifier">Iterator</span></code> should model <a class="link" href="../concepts/traversal.html#iterator.concepts.traversal.single_pass" title="Single Pass Iterator Concept">Single Pass Iterator</a>. 62 </p> 63<h5> 64<a name="iterator.algorithms.distance.h4"></a> 65 <span class="phrase"><a name="iterator.algorithms.distance.preconditions"></a></span><a class="link" href="distance.html#iterator.algorithms.distance.preconditions">Preconditions</a> 66 </h5> 67<p> 68 If <code class="computeroutput"><span class="identifier">Iterator</span></code> models <a class="link" href="../concepts/traversal.html#iterator.concepts.traversal.random_access" title="Random Access Traversal Concept">Random Access Traversal 69 Iterator</a>, <code class="computeroutput"><span class="special">[</span><span class="identifier">first</span><span class="special">,</span> <span class="identifier">last</span><span class="special">)</span></code> or <code class="computeroutput"><span class="special">[</span><span class="identifier">last</span><span class="special">,</span> <span class="identifier">first</span><span class="special">)</span></code> 70 should be valid; otherwise <code class="computeroutput"><span class="special">[</span><span class="identifier">first</span><span class="special">,</span> <span class="identifier">last</span><span class="special">)</span></code> should 71 be valid. 72 </p> 73<h5> 74<a name="iterator.algorithms.distance.h5"></a> 75 <span class="phrase"><a name="iterator.algorithms.distance.complexity"></a></span><a class="link" href="distance.html#iterator.algorithms.distance.complexity">Complexity</a> 76 </h5> 77<p> 78 If <code class="computeroutput"><span class="identifier">Iterator</span></code> models <a class="link" href="../concepts/traversal.html#iterator.concepts.traversal.random_access" title="Random Access Traversal Concept">Random Access Traversal 79 Iterator</a>, it takes constant time; otherwise it takes linear time. 80 </p> 81<h5> 82<a name="iterator.algorithms.distance.h6"></a> 83 <span class="phrase"><a name="iterator.algorithms.distance.notes"></a></span><a class="link" href="distance.html#iterator.algorithms.distance.notes">Notes</a> 84 </h5> 85<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 86<li class="listitem"> 87 This function is not a customization point and is protected against being 88 found by argument-dependent lookup (ADL). 89 </li> 90<li class="listitem"> 91 This function is <code class="computeroutput"><span class="keyword">constexpr</span></code> 92 only in C++14 or later. 93 </li> 94</ul></div> 95<h5> 96<a name="iterator.algorithms.distance.h7"></a> 97 <span class="phrase"><a name="iterator.algorithms.distance.acknowledgements"></a></span><a class="link" href="distance.html#iterator.algorithms.distance.acknowledgements">Acknowledgements</a> 98 </h5> 99<p> 100 Contributed by Michel Morin. 101 </p> 102</div> 103<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 104<td align="left"></td> 105<td align="right"><div class="copyright-footer">Copyright © 2003, 2005 David Abrahams Jeremy Siek Thomas 106 Witt<p> 107 Distributed under the Boost Software License, Version 1.0. (See accompanying 108 file LICENSE_1_0.txt or copy at <ulink url="http://www.boost.org/LICENSE_1_0.txt"> 109 http://www.boost.org/LICENSE_1_0.txt </ulink>) 110 </p> 111</div></td> 112</tr></table> 113<hr> 114<div class="spirit-nav"> 115<a accesskey="p" href="../algorithms.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../algorithms.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="next_prior.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 116</div> 117</body> 118</html> 119