<?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_MSG</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="./assert.html" class="navigation-link">Prev</a> <a href="./assert-not.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./assert.html" class="navigation-link">Back</a> <a href="./assert-not.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-msg.html" class="navigation-link">BOOST_MPL_ASSERT_MSG</a></td> </tr></table><div class="header-separator"></div> <div class="section" id="boost-mpl-assert-msg"> <h1><a class="toc-backref" href="./asserts.html#id1589">BOOST_MPL_ASSERT_MSG</a></h1> <div class="section" id="id1294"> <h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> <pre class="literal-block"> #define <a href="./assert-msg.html" class="identifier">BOOST_MPL_ASSERT_MSG</a>( condition, message, types ) \ <em>unspecified token sequence</em> \ /**/ </pre> </div> <div class="section" id="id1295"> <h3><a class="subsection-title" href="#description" name="description">Description</a></h3> <p>Generates a compilation error with an embedded custom message when the condition doesn't hold.</p> </div> <div class="section" id="id1296"> <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="id1297"> <h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> <table border="1" class="docutils table"> <colgroup> <col width="15%" /> <col width="36%" /> <col width="48%" /> </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">condition</span></tt></td> <td>An integral constant expression</td> <td>A condition to be asserted.</td> </tr> <tr><td><tt class="literal"><span class="pre">message</span></tt></td> <td>A legal identifier token</td> <td>A custom message in a form of a legal C++ identifier token.</td> </tr> <tr><td><tt class="literal"><span class="pre">types</span></tt></td> <td>A legal function parameter list</td> <td>A parenthized list of types to be displayed in the error message.</td> </tr> </tbody> </table> </div> <div class="section" id="id1298"> <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> <p>For any integral constant expression <tt class="literal"><span class="pre">expr</span></tt>, legal C++ identifier <tt class="literal"><span class="pre">message</span></tt>, and arbitrary types <tt class="literal"><span class="pre">t1</span></tt>, <tt class="literal"><span class="pre">t2</span></tt>,... <tt class="literal"><span class="pre">tn</span></tt>:</p> <pre class="literal-block"> <a href="./assert-msg.html" class="identifier">BOOST_MPL_ASSERT_MSG</a>( expr, message, (t1, t2,... tn) ); </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">Precondition:</th><td class="field-body"><p class="first"><tt class="literal"><span class="pre">t1</span></tt>, <tt class="literal"><span class="pre">t2</span></tt>,... <tt class="literal"><span class="pre">tn</span></tt> are non-<tt class="literal"><span class="pre">void</span></tt>.</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">expr</span> <span class="pre">!=</span> <span class="pre">true</span></tt>, otherwise has no effect.</p> <p>When possible within the compiler's diagnostic capabilities, the error message will include the <tt class="literal"><span class="pre">message</span></tt> identifier and the parenthized list of <tt class="literal"><span class="pre">t1</span></tt>, <tt class="literal"><span class="pre">t2</span></tt>,... <tt class="literal"><span class="pre">tn</span></tt> types, and have a general form of:</p> <pre class="last literal-block"> <em>...</em> ************( <em>...</em>::message )************)(t1, t2,... tn) <em>...</em> </pre> </td> </tr> </tbody> </table> <pre class="literal-block"> <a href="./assert-msg.html" class="identifier">BOOST_MPL_ASSERT_MSG</a>( expr, message, (types<t1, t2,... tn>) ); </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">Precondition:</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">expr</span> <span class="pre">!=</span> <span class="pre">true</span></tt>, otherwise has no effect.</p> <p>When possible within the compiler's diagnostics capabilities, the error message will include the <tt class="literal"><span class="pre">message</span></tt> identifier and the list of <tt class="literal"><span class="pre">t1</span></tt>, <tt class="literal"><span class="pre">t2</span></tt>,... <tt class="literal"><span class="pre">tn</span></tt> types, and have a general form of:</p> <pre class="last literal-block"> <em>...</em> ************( <em>...</em>::message )************)(types<t1, t2,... tn>) <em>...</em> </pre> </td> </tr> </tbody> </table> </div> <div class="section" id="id1299"> <h3><a class="subsection-title" href="#example" name="example">Example</a></h3> <pre class="literal-block"> template< typename T > struct my { // ... <a href="./assert-msg.html" class="identifier">BOOST_MPL_ASSERT_MSG</a>( is_integral<T>::value , NON_INTEGRAL_TYPES_ARE_NOT_ALLOWED , (T) ); }; my<void*> test; // In instantiation of `my<void*>': // instantiated from here // conversion from ` // mpl_::failed************(my<void*>:: // NON_INTEGRAL_TYPES_ARE_NOT_ALLOWED::************)(void*) // ' to non-scalar type `mpl_::assert<false>' requested </pre> </div> <div class="section" id="id1300"> <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.html">BOOST_MPL_ASSERT</a>, <a class="reference internal" href="./assert-not.html">BOOST_MPL_ASSERT_NOT</a>, <a class="reference internal" href="./assert-relation.html">BOOST_MPL_ASSERT_RELATION</a></p> <!-- Macros/Asserts//BOOST_MPL_ASSERT_NOT --> </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="./assert.html" class="navigation-link">Prev</a> <a href="./assert-not.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./assert.html" class="navigation-link">Back</a> <a href="./assert-not.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>