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<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> <title>Chapter 1. Boost.Functional/OverloadedFunction 1.0.0</title> <link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css"> <meta name="generator" content="DocBook XSL Stylesheets V1.76.1"> <link rel="home" href="index.html" title="Chapter 1. Boost.Functional/OverloadedFunction 1.0.0"> <link rel="next" href="boost_functional_overloadedfunction/getting_started.html" title="Getting Started"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> <table cellpadding="2" width="100%"><tr> <td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../boost.png"></td> <td align="center"><a href="../../../../../index.html">Home</a></td> <td align="center"><a href="../../../../../libs/libraries.htm">Libraries</a></td> <td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> <td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> <td align="center"><a href="../../../../../more/index.htm">More</a></td> </tr></table> <hr> <div class="spirit-nav"><a accesskey="n" href="boost_functional_overloadedfunction/getting_started.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a></div> <div class="chapter"> <div class="titlepage"><div> <div><h2 class="title"> <a name="boost_functional_overloadedfunction"></a>Chapter 1. Boost.Functional/OverloadedFunction 1.0.0</h2></div> <div><div class="author"><h3 class="author"> Lorenzo Caminiti <code class="email"><<a class="email" href="mailto:lorcaminiti@gmail.com">lorcaminiti@gmail.com</a>></code> </h3></div></div> <div>Copyright © 2011, 2012 Lorenzo Caminiti</div> <div><div class="legalnotice"> <a name="boost_functional_overloadedfunction.legal"></a> Distributed under the Boost Software License, Version 1.0 (see accompanying file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) </div></div> </div></div> <div class="toc"> Table of Contents <dl> <dt><a href="index.html#boost_functional_overloadedfunction.introduction">Introduction</a></dt> <dt><a href="boost_functional_overloadedfunction/getting_started.html">Getting Started</a></dt> <dd><dl> <dt><a href="boost_functional_overloadedfunction/getting_started.html#boost_functional_overloadedfunction.getting_started.compilers_and_platforms">Compilers and Platforms</a></dt> <dt><a href="boost_functional_overloadedfunction/getting_started.html#boost_functional_overloadedfunction.getting_started.installation">Installation</a></dt> </dl></dd> <dt><a href="boost_functional_overloadedfunction/tutorial.html">Tutorial</a></dt> <dd><dl> <dt><a href="boost_functional_overloadedfunction/tutorial.html#boost_functional_overloadedfunction.tutorial.overloading">Overloading</a></dt> <dt><a href="boost_functional_overloadedfunction/tutorial.html#boost_functional_overloadedfunction.tutorial.without_function_types">Without Function Types</a></dt> </dl></dd> <dt><a href="reference.html">Reference</a></dt> <dd><dl> <dt><a href="reference.html#header.boost.functional.overloaded_function_hpp">Header <boost/functional/overloaded_function.hpp></a></dt> <dt><a href="reference.html#header.boost.functional.overloaded_function.config_hpp">Header <boost/functional/overloaded_function/config.hpp></a></dt> </dl></dd> <dt><a href="boost_functional_overloadedfunction/acknowledgments.html">Acknowledgments</a></dt> </dl> </div> This library allows to overload different functions into a single function object. <div class="section boost_functional_overloadedfunction_introduction"> <div class="titlepage"><div><div><h2 class="title" style="clear: both"> <a name="boost_functional_overloadedfunction.introduction"></a><a class="link" href="index.html#boost_functional_overloadedfunction.introduction" title="Introduction">Introduction</a> </h2></div></div></div> Consider the following functions which have distinct signatures: <pre class="programlisting">const std::string& identity_s(const std::string& x) // Function (as pointer). { return x; } int identity_i_impl(int x) { return x; } int (&identity_i)(int) = identity_i_impl; // Function reference. double identity_d_impl(double x) { return x; } boost::function<double (double)> identity_d = identity_d_impl; // Functor. </pre> Instead of calling them using their separate names (here <code class="computeroutput">BOOST_TEST</code> is equivalent to <code class="computeroutput">assert</code>): [<a name="boost_functional_overloadedfunction.introduction.f0" href="#ftn.boost_functional_overloadedfunction.introduction.f0" class="footnote">1</a>] <pre class="programlisting">BOOST_TEST(identity_s("abc") == "abc"); BOOST_TEST(identity_i(123) == 123); BOOST_TEST(identity_d(1.23) == 1.23); </pre> It is possible to use this library to create a single <a href="http://en.wikipedia.org/wiki/Function_overloading" target="_top">overloaded</a> function object (or <a href="http://en.wikipedia.org/wiki/Functor" target="_top">functor</a>) named <code class="computeroutput">identity</code> that aggregates together the calls to the specific functions (see also <a href="../../test/functor.cpp" target="_top"><code class="literal">functor.cpp</code></a> and <a href="../../test/identity.hpp" target="_top"><code class="literal">identity.hpp</code></a>): <pre class="programlisting">boost::overloaded_function< const std::string& (const std::string&) , int (int) , double (double) > identity(identity_s, identity_i, identity_d); // All calls via single `identity` function. BOOST_TEST(identity("abc") == "abc"); BOOST_TEST(identity(123) == 123); BOOST_TEST(identity(1.23) == 1.23); </pre> Note how the functions are called via a single overloaded function object <code class="computeroutput">identity</code> instead of using their different names <code class="computeroutput">identity_s</code>, <code class="computeroutput">identity_i</code>, and <code class="computeroutput">identity_d</code>. </div> <div class="footnotes"> <hr width="100" align="left"> <div class="footnote">[<a id="ftn.boost_functional_overloadedfunction.introduction.f0" href="#boost_functional_overloadedfunction.introduction.f0" class="para">1</a>] In most of the examples presented in this documentation, the Boost.Detail/LightweightTest (<code class="literal">boost/detail/lightweight_test.hpp</code>) macro <code class="computeroutput">BOOST_TEST</code> is used to check correctness conditions (conceptually similar to <code class="computeroutput">assert</code>). A failure of the checked condition does not abort the execution of the program, it will instead make <code class="computeroutput">boost::report_errors</code> return a non-zero program exit code. Using Boost.Detail/LightweightTest allows to add the examples to the library regression tests so to make sure that they always compile and run correctly. </div> </div> </div> <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> <td align="left">Last revised: April 28, 2012 at 02:19:13 GMT</td> <td align="right"><div class="copyright-footer"></div></td> </tr></table> <hr> <div class="spirit-nav"><a accesskey="n" href="boost_functional_overloadedfunction/getting_started.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a></div> </body> </html>