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| <title>Serialization - BOOST_STATIC_WARNING</title> |
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| <h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../boost.png" border="0"></a></h3> |
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| <h1 align="center">Serialization</h1> |
| <h2 align="center"><code style="white-space: normal">BOOST_STRONG_TYPEDEF</code></h2> |
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| <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) |
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