1<?xml version="1.0" encoding="utf-8" ?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> 4<head> 5<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 6<meta name="generator" content="Docutils 0.7: http://docutils.sourceforge.net/" /> 7<title>The MPL Reference Manual: Concepts</title> 8<link rel="stylesheet" href="../style.css" type="text/css" /> 9</head> 10<body class="docframe refmanual"> 11<table class="header"><tr class="header"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./iterators.html" class="navigation-link">Prev</a> <a href="./forward-iterator.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group">Back <a href="./iterator-metafunctions.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./iterators.html" class="navigation-link">Up</a> <a href="../refmanual.html" class="navigation-link">Home</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./refmanual_toc.html" class="navigation-link">Full TOC</a></span></td> 12<td class="header-group page-location"><a href="../refmanual.html" class="navigation-link">Front Page</a> / <a href="./iterators.html" class="navigation-link">Iterators</a> / <a href="./iterators-concepts.html" class="navigation-link">Concepts</a></td> 13</tr></table><div class="header-separator"></div> 14<div class="section" id="id382"> 15<h1><a class="toc-backref" href="./iterators.html#id1449"><a class="subsection-title" href="#concepts" name="concepts">Concepts</a></a></h1> 16<p id="label-iterators-concepts">All iterators in MPL are classified into three iterator concepts, or 17<cite>categories</cite>, named according to the type of traversal provided. The 18categories are: <a class="reference internal" href="./forward-iterator.html">Forward Iterator</a>, <a class="reference internal" href="./bidirectional-iterator.html">Bidirectional Iterator</a>, and 19<a class="reference internal" href="./random-access-iterator.html">Random Access Iterator</a>. The concepts are hierarchical: 20<a class="reference internal" href="./random-access-iterator.html">Random Access Iterator</a> is a refinement of <a class="reference internal" href="./bidirectional-iterator.html">Bidirectional Iterator</a>, 21which, in its turn, is a refinement of <a class="reference internal" href="./forward-iterator.html">Forward Iterator</a>.</p> 22<p>Because of the inherently immutable nature of the value access, MPL 23iterators escape the problems of the traversal-only categorization 24discussed at length in <a class="citation-reference" href="#n1550" id="id383">[n1550]</a>.</p> 25<table class="docutils citation" frame="void" id="n1550" rules="none"> 26<colgroup><col class="label" /><col /></colgroup> 27<tbody valign="top"> 28<tr><td class="label"><a class="fn-backref" href="#id383">[n1550]</a></td><td><a class="reference external" href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2003/n1550.htm" target="_top">http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2003/n1550.htm</a></td></tr> 29</tbody> 30</table> 31<!-- Iterators/Concepts//Forward Iterator |10 --> 32<ul class="toc simple" id="outline"> 33<li><a class="reference internal" href="./forward-iterator.html" id="id1450">Forward Iterator</a></li> 34<li><a class="reference internal" href="./bidirectional-iterator.html" id="id1451">Bidirectional Iterator</a></li> 35<li><a class="reference internal" href="./random-access-iterator.html" id="id1452">Random Access Iterator</a></li> 36</ul> 37</div> 38 39<div class="footer-separator"></div> 40<table class="footer"><tr class="footer"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./iterators.html" class="navigation-link">Prev</a> <a href="./forward-iterator.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group">Back <a href="./iterator-metafunctions.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./iterators.html" class="navigation-link">Up</a> <a href="../refmanual.html" class="navigation-link">Home</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./refmanual_toc.html" class="navigation-link">Full TOC</a></span></td> 41<td><div class="copyright-footer"><div class="copyright">Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams</div> 42Distributed under the Boost Software License, Version 1.0. (See accompanying 43file LICENSE_1_0.txt or copy at <a class="reference external" href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)</div></td></tr></table></body> 44</html> 45