libs/functional/overloaded_function/doc/html/index.html

   1 <html>
   2 <head>
   3 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
   4 <title>Chapter&#160;1.&#160;Boost.Functional/OverloadedFunction 1.0.0</title>
   5 <link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css">
   6 <meta name="generator" content="DocBook XSL Stylesheets V1.79.1">
   7 <link rel="home" href="index.html" title="Chapter&#160;1.&#160;Boost.Functional/OverloadedFunction 1.0.0">
   8 <link rel="next" href="boost_functional_overloadedfunction/getting_started.html" title="Getting Started">
   9 </head>
  10 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
  11 <table cellpadding="2" width="100%"><tr>
  12 <td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../boost.png"></td>
  13 <td align="center"><a href="../../../../../index.html">Home</a></td>
  14 <td align="center"><a href="../../../../../libs/libraries.htm">Libraries</a></td>
  15 <td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
  16 <td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
  17 <td align="center"><a href="../../../../../more/index.htm">More</a></td>
  18 </tr></table>
  19 <hr>
  20 <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>
  21 <div class="chapter">
  22 <div class="titlepage"><div>
  23 <div><h2 class="title">
  24 <a name="boost_functional_overloadedfunction"></a>Chapter&#160;1.&#160;Boost.Functional/OverloadedFunction 1.0.0</h2></div>
  25 <div><div class="author"><h3 class="author">
  26 <span class="firstname">Lorenzo</span> <span class="surname">Caminiti <code class="email">&lt;<a class="email" href="mailto:lorcaminiti@gmail.com">lorcaminiti@gmail.com</a>&gt;</code></span>
  27 </h3></div></div>
  28 <div><p class="copyright">Copyright &#169; 2011, 2012 Lorenzo Caminiti</p></div>
  29 <div><div class="legalnotice">
  30 <a name="boost_functional_overloadedfunction.legal"></a><p>
  31         Distributed under the Boost Software License, Version 1.0 (see accompanying
  32         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>)
  33       </p>
  34 </div></div>
  35 </div></div>
  36 <div class="toc">
  37 <p><b>Table of Contents</b></p>
  38 <dl class="toc">
  39 <dt><span class="section"><a href="index.html#boost_functional_overloadedfunction.introduction">Introduction</a></span></dt>
  40 <dt><span class="section"><a href="boost_functional_overloadedfunction/getting_started.html">Getting
  41     Started</a></span></dt>
  42 <dd><dl>
  43 <dt><span class="section"><a href="boost_functional_overloadedfunction/getting_started.html#boost_functional_overloadedfunction.getting_started.compilers_and_platforms">Compilers
  44       and Platforms</a></span></dt>
  45 <dt><span class="section"><a href="boost_functional_overloadedfunction/getting_started.html#boost_functional_overloadedfunction.getting_started.installation">Installation</a></span></dt>
  46 </dl></dd>
  47 <dt><span class="section"><a href="boost_functional_overloadedfunction/tutorial.html">Tutorial</a></span></dt>
  48 <dd><dl>
  49 <dt><span class="section"><a href="boost_functional_overloadedfunction/tutorial.html#boost_functional_overloadedfunction.tutorial.overloading">Overloading</a></span></dt>
  50 <dt><span class="section"><a href="boost_functional_overloadedfunction/tutorial.html#boost_functional_overloadedfunction.tutorial.without_function_types">Without
  51       Function Types</a></span></dt>
  52 </dl></dd>
  53 <dt><span class="section"><a href="reference.html">Reference</a></span></dt>
  54 <dt><span class="section"><a href="boost_functional_overloadedfunction/acknowledgments.html">Acknowledgments</a></span></dt>
  55 </dl>
  56 </div>
  57 <p>
  58     This library allows to overload different functions into a single function object.
  59   </p>
  60 <div class="section">
  61 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
  62 <a name="boost_functional_overloadedfunction.introduction"></a><a class="link" href="index.html#boost_functional_overloadedfunction.introduction" title="Introduction">Introduction</a>
  63 </h2></div></div></div>
  64 <p>
  65       Consider the following functions which have distinct signatures:
  66     </p>
  67 <p>
  68 </p>
  69 <pre class="programlisting"><span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&amp;</span> <span class="identifier">identity_s</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&amp;</span> <span class="identifier">x</span><span class="special">)</span> <span class="comment">// Function (as pointer).</span>
  70     <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">x</span><span class="special">;</span> <span class="special">}</span>
  71
  72 <span class="keyword">int</span> <span class="identifier">identity_i_impl</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">x</span><span class="special">)</span> <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">x</span><span class="special">;</span> <span class="special">}</span>
  73 <span class="keyword">int</span> <span class="special">(&amp;</span><span class="identifier">identity_i</span><span class="special">)(</span><span class="keyword">int</span><span class="special">)</span> <span class="special">=</span> <span class="identifier">identity_i_impl</span><span class="special">;</span> <span class="comment">// Function reference.</span>
  74
  75 <span class="keyword">double</span> <span class="identifier">identity_d_impl</span><span class="special">(</span><span class="keyword">double</span> <span class="identifier">x</span><span class="special">)</span> <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">x</span><span class="special">;</span> <span class="special">}</span>
  76 <span class="identifier">boost</span><span class="special">::</span><span class="identifier">function</span><span class="special">&lt;</span><span class="keyword">double</span> <span class="special">(</span><span class="keyword">double</span><span class="special">)&gt;</span> <span class="identifier">identity_d</span> <span class="special">=</span> <span class="identifier">identity_d_impl</span><span class="special">;</span> <span class="comment">// Functor.</span>
  77 </pre>
  78 <p>
  79     </p>
  80 <p>
  81       Instead of calling them using their separate names (here <code class="computeroutput"><span class="identifier">BOOST_TEST</span></code>
  82       is equivalent to <code class="computeroutput"><span class="identifier">assert</span></code>):
  83       <a href="#ftn.boost_functional_overloadedfunction.introduction.f0" class="footnote" name="boost_functional_overloadedfunction.introduction.f0"><sup class="footnote">[1]</sup></a>
  84     </p>
  85 <p>
  86 </p>
  87 <pre class="programlisting"><span class="identifier">BOOST_TEST</span><span class="special">(</span><span class="identifier">identity_s</span><span class="special">(</span><span class="string">"abc"</span><span class="special">)</span> <span class="special">==</span> <span class="string">"abc"</span><span class="special">);</span>
  88 <span class="identifier">BOOST_TEST</span><span class="special">(</span><span class="identifier">identity_i</span><span class="special">(</span><span class="number">123</span><span class="special">)</span> <span class="special">==</span> <span class="number">123</span><span class="special">);</span>
  89 <span class="identifier">BOOST_TEST</span><span class="special">(</span><span class="identifier">identity_d</span><span class="special">(</span><span class="number">1.23</span><span class="special">)</span> <span class="special">==</span> <span class="number">1.23</span><span class="special">);</span>
  90 </pre>
  91 <p>
  92     </p>
  93 <p>
  94       It is possible to use this library to create a single <a href="http://en.wikipedia.org/wiki/Function_overloading" target="_top">overloaded</a>
  95       function object (or <a href="http://en.wikipedia.org/wiki/Functor" target="_top">functor</a>)
  96       named <code class="computeroutput"><span class="identifier">identity</span></code> that aggregates
  97       together the calls to the specific functions (see also <a href="../../test/functor.cpp" target="_top"><code class="literal">functor.cpp</code></a>
  98       and <a href="../../test/identity.hpp" target="_top"><code class="literal">identity.hpp</code></a>):
  99     </p>
 100 <p>
 101 </p>
 102 <pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">overloaded_function</span><span class="special">&lt;</span>
 103       <span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&amp;</span> <span class="special">(</span><span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&amp;)</span>
 104     <span class="special">,</span> <span class="keyword">int</span> <span class="special">(</span><span class="keyword">int</span><span class="special">)</span>
 105     <span class="special">,</span> <span class="keyword">double</span> <span class="special">(</span><span class="keyword">double</span><span class="special">)</span>
 106 <span class="special">&gt;</span> <span class="identifier">identity</span><span class="special">(</span><span class="identifier">identity_s</span><span class="special">,</span> <span class="identifier">identity_i</span><span class="special">,</span> <span class="identifier">identity_d</span><span class="special">);</span>
 107
 108 <span class="comment">// All calls via single `identity` function.</span>
 109 <span class="identifier">BOOST_TEST</span><span class="special">(</span><span class="identifier">identity</span><span class="special">(</span><span class="string">"abc"</span><span class="special">)</span> <span class="special">==</span> <span class="string">"abc"</span><span class="special">);</span>
 110 <span class="identifier">BOOST_TEST</span><span class="special">(</span><span class="identifier">identity</span><span class="special">(</span><span class="number">123</span><span class="special">)</span> <span class="special">==</span> <span class="number">123</span><span class="special">);</span>
 111 <span class="identifier">BOOST_TEST</span><span class="special">(</span><span class="identifier">identity</span><span class="special">(</span><span class="number">1.23</span><span class="special">)</span> <span class="special">==</span> <span class="number">1.23</span><span class="special">);</span>
 112 </pre>
 113 <p>
 114     </p>
 115 <p>
 116       Note how the functions are called via a single overloaded function object
 117       <code class="computeroutput"><span class="identifier">identity</span></code> instead of using their
 118       different names <code class="computeroutput"><span class="identifier">identity_s</span></code>,
 119       <code class="computeroutput"><span class="identifier">identity_i</span></code>, and <code class="computeroutput"><span class="identifier">identity_d</span></code>.
 120     </p>
 121 </div>
 122 <div class="footnotes">
 123 <br><hr style="width:100; text-align:left;margin-left: 0">
 124 <div id="ftn.boost_functional_overloadedfunction.introduction.f0" class="footnote"><p><a href="#boost_functional_overloadedfunction.introduction.f0" class="para"><sup class="para">[1] </sup></a>
 125         In most of the examples presented in this documentation, the Boost.Core/LightweightTest
 126         (<code class="literal">boost/core/lightweight_test.hpp</code>) macro <code class="computeroutput"><span class="identifier">BOOST_TEST</span></code> is used to check correctness
 127         conditions (conceptually similar to <code class="computeroutput"><span class="identifier">assert</span></code>).
 128         A failure of the checked condition does not abort the execution of the program,
 129         it will instead make <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">report_errors</span></code>
 130         return a non-zero program exit code. Using Boost.Core/LightweightTest allows
 131         to add the examples to the library regression tests so to make sure that
 132         they always compile and run correctly.
 133       </p></div>
 134 </div>
 135 </div>
 136 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 137 <td align="left"><p><small>Last revised: December 10, 2019 at 00:23:32 GMT</small></p></td>
 138 <td align="right"><div class="copyright-footer"></div></td>
 139 </tr></table>
 140 <hr>
 141 <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>
 142 </body>
 143 </html>