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: BOOST_MPL_ASSERT_RELATION</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="./assert-not.html" class="navigation-link">Prev</a> <a href="./introspection.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./assert-not.html" class="navigation-link">Back</a> Along</span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./asserts.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="./macros.html" class="navigation-link">Macros</a> / <a href="./asserts.html" class="navigation-link">Asserts</a> / <a href="./assert-relation.html" class="navigation-link">BOOST_MPL_ASSERT_RELATION</a></td> 13</tr></table><div class="header-separator"></div> 14<div class="section" id="boost-mpl-assert-relation"> 15<h1><a class="toc-backref" href="./asserts.html#id1591">BOOST_MPL_ASSERT_RELATION</a></h1> 16<div class="section" id="id1308"> 17<h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> 18<pre class="literal-block"> 19#define <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( x, relation, y ) \ 20 <em>unspecified token sequence</em> \ 21/**/ 22</pre> 23</div> 24<div class="section" id="id1309"> 25<h3><a class="subsection-title" href="#description" name="description">Description</a></h3> 26<p>A specialized assertion macro for checking numerical conditions. Generates 27a compilation error when the condition <tt class="literal"><span class="pre">(</span> <span class="pre">x</span> <span class="pre">relation</span> <span class="pre">y</span> <span class="pre">)</span></tt> 28doesn't hold.</p> 29</div> 30<div class="section" id="id1310"> 31<h3><a class="subsection-title" href="#header" name="header">Header</a></h3> 32<pre class="literal-block"> 33#include <<a href="../../../../boost/mpl/assert.hpp" class="header">boost/mpl/assert.hpp</a>> 34</pre> 35</div> 36<div class="section" id="id1311"> 37<h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> 38<table border="1" class="docutils table"> 39<colgroup> 40<col width="15%" /> 41<col width="36%" /> 42<col width="48%" /> 43</colgroup> 44<thead valign="bottom"> 45<tr><th class="head">Parameter</th> 46<th class="head">Requirement</th> 47<th class="head">Description</th> 48</tr> 49</thead> 50<tbody valign="top"> 51<tr><td><tt class="literal"><span class="pre">x</span></tt></td> 52<td>An integral constant</td> 53<td>Left operand of the checked relation.</td> 54</tr> 55<tr><td><tt class="literal"><span class="pre">y</span></tt></td> 56<td>An integral constant</td> 57<td>Right operand of the checked relation.</td> 58</tr> 59<tr><td><tt class="literal"><span class="pre">relation</span></tt></td> 60<td>A C++ operator token</td> 61<td>An operator token for the relation being 62checked.</td> 63</tr> 64</tbody> 65</table> 66</div> 67<div class="section" id="id1312"> 68<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> 69<p>For any integral constants <tt class="literal"><span class="pre">x</span></tt>, <tt class="literal"><span class="pre">y</span></tt> and a legal C++ operator token <tt class="literal"><span class="pre">op</span></tt>:</p> 70<pre class="literal-block"> 71<a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( x, op, y ); 72</pre> 73<table class="docutils field-list" frame="void" rules="none"> 74<col class="field-name" /> 75<col class="field-body" /> 76<tbody valign="top"> 77<tr class="field"><th class="field-name">Return type:</th><td class="field-body"><p class="first">None.</p> 78</td> 79</tr> 80<tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Generates a compilation error if <tt class="literal"><span class="pre">(</span> <span class="pre">x</span> <span class="pre">op</span> <span class="pre">y</span> <span class="pre">)</span> <span class="pre">!=</span> <span class="pre">true</span></tt>, otherwise 81has no effect.</p> 82<p>When possible within the compiler's diagnostic capabilities, 83the error message will include a name of the relation being checked, 84the actual values of both operands, and have a general form of:</p> 85<pre class="last literal-block"> 86<em>...</em> ************<em>...</em>assert_relation<op, x, y>::************) <em>...</em> 87</pre> 88</td> 89</tr> 90</tbody> 91</table> 92</div> 93<div class="section" id="id1313"> 94<h3><a class="subsection-title" href="#example" name="example">Example</a></h3> 95<pre class="literal-block"> 96template< typename T, typename U > struct my 97{ 98 // ... 99 <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( sizeof(T), <, sizeof(U) ); 100}; 101 102my<char[50],char[10]> test; 103 104// In instantiation of `my<char[50], char[10]>': 105// instantiated from here 106// conversion from ` 107// mpl_::failed************mpl_::assert_relation<<a href="./less.html" class="identifier">less</a>, 50, 10>::************' 108// to non-scalar type `mpl_::assert<false>' requested 109</pre> 110</div> 111<div class="section" id="id1314"> 112<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3> 113<p><a class="reference internal" href="./asserts.html">Asserts</a>, <a class="reference internal" href="./assert.html">BOOST_MPL_ASSERT</a>, <a class="reference internal" href="./assert-not.html">BOOST_MPL_ASSERT_NOT</a>, <a class="reference internal" href="./assert-msg.html">BOOST_MPL_ASSERT_MSG</a></p> 114</div> 115</div> 116 117<div class="footer-separator"></div> 118<table class="footer"><tr class="footer"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./assert-not.html" class="navigation-link">Prev</a> <a href="./introspection.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./assert-not.html" class="navigation-link">Back</a> Along</span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./asserts.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> 119<td><div class="copyright-footer"><div class="copyright">Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams</div> 120Distributed under the Boost Software License, Version 1.0. (See accompanying 121file 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> 122</html> 123