<?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"> <!-- Copyright Aleksey Gurtovoy 2006. Distributed under the Boost --> <!-- Software License, Version 1.0. (See accompanying --> <!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) --> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <meta name="generator" content="Docutils 0.3.6: http://docutils.sourceforge.net/" /> <title>THE BOOST MPL LIBRARY: Numeric Metafunction Protocol/Infrastructure</title> <link rel="stylesheet" href="../style.css" type="text/css" /> </head> <body class="docframe"> <table class="header"><tr class="header"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./tag-dispatching-protocol.html" class="navigation-link">Prev</a> <a href="./renaming-cleanup.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./tag-dispatching-protocol.html" class="navigation-link">Back</a> <a href="./renaming-cleanup.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./changes-in-boost-1-32-0.html" class="navigation-link">Up</a> <a href="../index.html" class="navigation-link">Home</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./tutorial_toc.html" class="navigation-link">Full TOC</a></span></td> <td class="header-group page-location"><a href="../index.html" class="navigation-link">Front Page</a> / <a href="./changelog-history.html" class="navigation-link">Changelog & History</a> / <a href="./changes-in-boost-1-32-0.html" class="navigation-link">Changes in Boost 1.32.0 Release</a> / <a href="./numeric-metafunction.html" class="navigation-link">Numeric Metafunction Protocol/Infrastructure</a></td> </tr></table><div class="header-separator"></div> <div class="section" id="numeric-metafunction"> <h1><a class="toc-backref" href="./changes-in-boost-1-32-0.html#id67" name="numeric-metafunction">Numeric Metafunction Protocol/Infrastructure</a></h1> <p>The arithmetic, comparison and bitwise metafunctions are now <cite>polymorphic</cite>, and can operate on a variety of numeric types, including rational, fixed-point and complex numbers. They allow <cite>mixed arithmetic</cite>, meaning that you can perform an operation on arguments of different types, and the result will yield the largest/most general of the argument types. The infrastructure allows user-defined numeric types to be freely intermixed with predefined library types. See <a class="reference" href="http://cvs.sourceforge.net/viewcvs.py/boost/boost/libs/mpl/test/numeric_ops.cpp?view=markup" target="_top">http://cvs.sourceforge.net/viewcvs.py/boost/boost/libs/mpl/test/numeric_ops.cpp?view=markup</a> for an illustrative example, and the <a class="reference" href="./reference-manual.html">reference manual</a> for the formal infrastructure specification.</p> <p>If you were using MPL numeric metafunctions on your own integral wrapper class similar to <tt class="literal"><span class="pre">mpl::int_</span></tt>, you can plug your class into the new infrastructure by extending it with the following member:</p> <pre class="literal-block"> typedef mpl::integral_c_tag tag; </pre> <p>For example:</p> <table border="1" class="table"> <colgroup> <col width="48%" /> <col width="52%" /> </colgroup> <thead valign="bottom"> <tr><th>Before</th> <th>Now</th> </tr> </thead> <tbody valign="top"> <tr><td><pre class="first last literal-block"> template< int n > struct my_int { static int const value = n; typedef my_int type; }; </pre> </td> <td><pre class="first last literal-block"> template< int n > struct my_int { <strong>typedef mpl::integral_c_tag tag;</strong> static int const value = n; typedef my_int type; }; </pre> </td> </tr> </tbody> </table> </div> <div class="footer-separator"></div> <table class="footer"><tr class="footer"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./tag-dispatching-protocol.html" class="navigation-link">Prev</a> <a href="./renaming-cleanup.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./tag-dispatching-protocol.html" class="navigation-link">Back</a> <a href="./renaming-cleanup.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./changes-in-boost-1-32-0.html" class="navigation-link">Up</a> <a href="../index.html" class="navigation-link">Home</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./tutorial_toc.html" class="navigation-link">Full TOC</a></span></td> </tr></table></body> </html>