<!doctype HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <!-- (C) Copyright 2002-4 Robert Ramey - http://www.rrsd.com . Use, modification and distribution is subject to 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"> <link rel="stylesheet" type="text/css" href="../../../boost.css"> <link rel="stylesheet" type="text/css" href="style.css"> <title>Serialization - BOOST_STATIC_WARNING</title> </head> <body link="#0000ff" vlink="#800080"> <table border="0" cellpadding="7" cellspacing="0" width="100%" summary="header"> <tr> <td valign="top" width="300"> <h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../boost.png" border="0"></a></h3> </td> <td valign="top"> <h1 align="center">Serialization</h1> <h2 align="center"><code style="white-space: normal">BOOST_STRONG_TYPEDEF</code></h2> </td> </tr> </table> <hr> <h3>Motivation</h3> <code style="white-space: normal">typedef</code> creates an alias for an existing type. It does not create a new type that can be used for matching either function or template parameters. This can be shown by trying to compile the following example. <pre></code> typedef int a; void f(int x); // (1) function to handle simple integers void f(a x); // (2) special function to handle integers of type a int main(){ int x = 1; a y; y = x; // other operations permitted as a is converted as necessary f(x); // chooses (1) f(y); // chooses (2) } </code></pre> Since typedef doesn't create a new type, this program can't compile to code that implements its obvious intention. <p> Usage of BOOST_STRONG_TYPEDEF addresses this. <pre></code> <a target="strong_typedef" href="../../../boost/strong_typedef.hpp"> #include <boost/serialization/strong_typedef.hpp> </a> BOOST_STRONG_TYPEDEF(int, a) void f(int x); // (1) function to handle simple integers void f(a x); // (2) special function to handle integers of type a int main(){ int x = 1; a y; y = x; // other operations permitted as a is converted as necessary f(x); // chooses (1) f(y); // chooses (2) } </code></pre> The program will now compile and run as expected. <h3>Usage</h3> Syntax of <code style="white-space: normal">BOOST_STRONG_TYPEDEF</code> has been designed to be similar to the standard <code style="white-space: normal">typedef</code>. So <pre><code> BOOST_STRONG_TYPEDEF(primitive type, name) </code></pre> will create a new type "name" which will be substitutable for the original type but still of distinct type. <h3>Implemenation</h3> <code style="white-space: normal">BOOST_STRONG_TYPEDEF</code> is a macro which generates a class named "name" wraps and instance of its primitive type and provides appropriate conversion operators in order to make the new type substitutable for the one that it wraps. <hr> <p><i>© Copyright <a href="http://www.rrsd.com">Robert Ramey</a> 2002-2004. 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) </i></p> </body> </html>