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: sizeof_</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="./max.html" class="navigation-link">Prev</a> <a href="./data-types.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./max.html" class="navigation-link">Back</a> Along</span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./miscellaneous.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="./metafunctions.html" class="navigation-link">Metafunctions</a> / <a href="./miscellaneous.html" class="navigation-link">Miscellaneous</a> / <a href="./sizeof.html" class="navigation-link">sizeof_</a></td> 13</tr></table><div class="header-separator"></div> 14<div class="section" id="sizeof"> 15<h1><a class="toc-backref" href="./miscellaneous.html#id1571">sizeof_</a></h1> 16<div class="section" id="id1207"> 17<h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> 18<pre class="literal-block"> 19template< 20 typename X 21 > 22struct <a href="./sizeof.html" class="identifier">sizeof_</a> 23{ 24 typedef <em>unspecified</em> type; 25}; 26</pre> 27</div> 28<div class="section" id="id1208"> 29<h3><a class="subsection-title" href="#description" name="description">Description</a></h3> 30<p>Returns the result of a <tt class="literal"><span class="pre">sizeof(X)</span></tt> expression wrapped into an 31<a class="reference internal" href="./integral-constant.html">Integral Constant</a> of the corresponding type, <tt class="literal"><span class="pre">std::<a href="./size-t.html" class="identifier">size_t</a></span></tt>.</p> 32</div> 33<div class="section" id="id1209"> 34<h3><a class="subsection-title" href="#header" name="header">Header</a></h3> 35<pre class="literal-block"> 36#include <<a href="../../../../boost/mpl/sizeof.hpp" class="header">boost/mpl/sizeof.hpp</a>> 37</pre> 38</div> 39<div class="section" id="id1210"> 40<h3><a class="subsection-title" href="#model-of" name="model-of">Model of</a></h3> 41<p><a class="reference internal" href="./metafunction.html">Metafunction</a></p> 42</div> 43<div class="section" id="id1211"> 44<h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> 45<table border="1" class="docutils table"> 46<colgroup> 47<col width="19%" /> 48<col width="25%" /> 49<col width="56%" /> 50</colgroup> 51<thead valign="bottom"> 52<tr><th class="head">Parameter</th> 53<th class="head">Requirement</th> 54<th class="head">Description</th> 55</tr> 56</thead> 57<tbody valign="top"> 58<tr><td><tt class="literal"><span class="pre">X</span></tt></td> 59<td>Any type</td> 60<td>A type to compute the <tt class="literal"><span class="pre">sizeof</span></tt> for.</td> 61</tr> 62</tbody> 63</table> 64</div> 65<div class="section" id="id1212"> 66<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> 67<p>For an arbitrary type <tt class="literal"><span class="pre">x</span></tt>:</p> 68<pre class="literal-block"> 69typedef <a href="./sizeof.html" class="identifier">sizeof_</a><x>::type n; 70</pre> 71<table class="docutils field-list" frame="void" rules="none"> 72<col class="field-name" /> 73<col class="field-body" /> 74<tbody valign="top"> 75<tr class="field"><th class="field-name">Return type:</th><td class="field-body"><p class="first"><a class="reference internal" href="./integral-constant.html">Integral Constant</a>.</p> 76</td> 77</tr> 78<tr class="field"><th class="field-name">Precondition:</th><td class="field-body"><p class="first"><tt class="literal"><span class="pre">x</span></tt> is a complete type.</p> 79</td> 80</tr> 81<tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Equivalent to</p> 82<pre class="last literal-block"> 83typedef <a href="./size-t.html" class="identifier">size_t</a>< sizeof(x) > n; 84</pre> 85</td> 86</tr> 87</tbody> 88</table> 89</div> 90<div class="section" id="id1213"> 91<h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3> 92<p>Constant time.</p> 93</div> 94<div class="section" id="id1214"> 95<h3><a class="subsection-title" href="#example" name="example">Example</a></h3> 96<pre class="literal-block"> 97struct udt { char a[100]; }; 98 99<a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( <a href="./sizeof.html" class="identifier">sizeof_</a><char>::value, ==, sizeof(char) ); 100<a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( <a href="./sizeof.html" class="identifier">sizeof_</a><int>::value, ==, sizeof(int) ); 101<a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( <a href="./sizeof.html" class="identifier">sizeof_</a><double>::value, ==, sizeof(double) ); 102<a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( <a href="./sizeof.html" class="identifier">sizeof_</a><udt>::value, ==, sizeof(my) ); 103</pre> 104</div> 105<div class="section" id="id1215"> 106<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3> 107<p><a class="reference internal" href="./metafunctions.html">Metafunctions</a>, <a class="reference internal" href="./integral-constant.html">Integral Constant</a>, <a class="reference internal" href="./size-t.html">size_t</a></p> 108</div> 109</div> 110 111<div class="footer-separator"></div> 112<table class="footer"><tr class="footer"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./max.html" class="navigation-link">Prev</a> <a href="./data-types.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./max.html" class="navigation-link">Back</a> Along</span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./miscellaneous.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> 113<td><div class="copyright-footer"><div class="copyright">Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams</div> 114Distributed under the Boost Software License, Version 1.0. (See accompanying 115file 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> 116</html> 117