<?xml version="1.0" encoding="utf-8" ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <meta name="generator" content="Docutils 0.7: http://docutils.sourceforge.net/" /> <title>The MPL Reference Manual: BOOST_MPL_ASSERT</title> <link rel="stylesheet" href="../style.css" type="text/css" /> </head> <body class="docframe refmanual"> <table class="header"><tr class="header"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./asserts.html" class="navigation-link">Prev</a> <a href="./assert-msg.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group">Back <a href="./assert-msg.html" class="navigation-link">Along</a></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> <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.html" class="navigation-link">BOOST_MPL_ASSERT</a></td> </tr></table><div class="header-separator"></div> <div class="section" id="boost-mpl-assert"> <h1><a class="toc-backref" href="./asserts.html#id1588">BOOST_MPL_ASSERT</a></h1> <div class="section" id="id1287"> <h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> <pre class="literal-block"> #define <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>( pred ) \ <em>unspecified token sequence</em> \ /**/ </pre> </div> <div class="section" id="id1288"> <h3><a class="subsection-title" href="#description" name="description">Description</a></h3> <p>Generates a compilation error when the predicate <tt class="literal"><span class="pre">pred</span></tt> holds false.</p> </div> <div class="section" id="id1289"> <h3><a class="subsection-title" href="#header" name="header">Header</a></h3> <pre class="literal-block"> #include <<a href="../../../../boost/mpl/assert.hpp" class="header">boost/mpl/assert.hpp</a>> </pre> </div> <div class="section" id="id1290"> <h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> <table border="1" class="docutils table"> <colgroup> <col width="19%" /> <col width="43%" /> <col width="38%" /> </colgroup> <thead valign="bottom"> <tr><th class="head">Parameter</th> <th class="head">Requirement</th> <th class="head">Description</th> </tr> </thead> <tbody valign="top"> <tr><td><tt class="literal"><span class="pre">pred</span></tt></td> <td>Boolean nullary <a class="reference internal" href="./metafunction.html">Metafunction</a></td> <td>A predicate to be asserted.</td> </tr> </tbody> </table> </div> <div class="section" id="id1291"> <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> <p>For any boolean nullary <a class="reference internal" href="./metafunction.html">Metafunction</a> <tt class="literal"><span class="pre">pred</span></tt>:</p> <pre class="literal-block"> <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( pred )); </pre> <table class="docutils field-list" frame="void" rules="none"> <col class="field-name" /> <col class="field-body" /> <tbody valign="top"> <tr class="field"><th class="field-name">Return type:</th><td class="field-body"><p class="first">None.</p> </td> </tr> <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">pred::type::value</span> <span class="pre">!=</span> <span class="pre">true</span></tt>, otherwise has no effect. Note that double parentheses are required even if no commas appear in the condition.</p> <p>When possible within the compiler's diagnostic capabilities, the error message will include the predicate's full type name, and have a general form of:</p> <pre class="last literal-block"> <em>...</em> ************ pred::************ <em>...</em> </pre> </td> </tr> </tbody> </table> </div> <div class="section" id="id1292"> <h3><a class="subsection-title" href="#example" name="example">Example</a></h3> <pre class="literal-block"> template< typename T, typename U > struct my { // ... <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same< T,U > )); }; my<void*,char*> test; // In instantiation of `my<void, char*>': // instantiated from here // conversion from ` // mpl_::failed************boost::is_same<void, char*>::************' to // non-scalar type `mpl_::assert<false>' requested </pre> </div> <div class="section" id="id1293"> <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3> <p><a class="reference internal" href="./asserts.html">Asserts</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>, <a class="reference internal" href="./assert-relation.html">BOOST_MPL_ASSERT_RELATION</a></p> <!-- Macros/Asserts//BOOST_MPL_ASSERT_MSG --> </div> </div> <div class="footer-separator"></div> <table class="footer"><tr class="footer"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./asserts.html" class="navigation-link">Prev</a> <a href="./assert-msg.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group">Back <a href="./assert-msg.html" class="navigation-link">Along</a></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> <td><div class="copyright-footer"><div class="copyright">Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams</div> Distributed under the Boost Software License, Version 1.0. (See accompanying file 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> </html>