preprocessor/doc/ref/overload.html
2016-04-14 08:52:06 -04:00

58 lines
3.1 KiB
HTML
Raw Permalink Blame History

<html>
<head>
<meta content="text/html; charset=windows-1252" http-equiv="content-type">
<title>BOOST_PP_OVERLOAD</title>
<link rel="stylesheet" type="text/css" href="../styles.css">
</head>
<body>
<div style="margin-left: 0px;"> The <b>BOOST_PP_OVERLOAD</b> variadic
macro expands to the name of a non-variadic macro having a given number of
parameters.<br>
</div>
<h4>Usage</h4>
<div class="code"> <b>BOOST_PP_OVERLOAD</b>(<i>prefix</i>,...) <a href="../topics/variadic_macros.html#VNotation"
target="_self"><sup>(v)</sup></a><br>
</div>
<h4>Arguments</h4>
<dl>
<dt>prefix<br>
</dt>
<dd> The prefix of the non-variadic macro name. </dd>
<dt>...<br>
</dt>
<dd><i> Variadic data</i>. The number of variadic data
elements, as determined by BOOST_PP_VARIADIC_SIZE, is appended to the
prefix to form the output non-variadic macro name.<br>
</dd>
</dl>
<h4>Remarks</h4>
<div> This macro creates a macro name which depends on the number of
elements of variadic data. It should be used in the form of <br>
BOOST_PP_OVERLOAD(MACRO_NAME_,__VA_ARGS__)(__VA_ARGS__) in order to
call a non-variadic macro taking a given number of variadic data
elements as non-variadic arguments. In this way one can invoke a
variadic macro with a variable number of parameters which calls one of
a series of non-variadic macros doing very similar things.
</div>
<b>Requirements</b>
<div> <b>Header:</b> &nbsp;<a href="../headers/facilities/overload.html">&lt;boost/preprocessor/facilities/overload.hpp&gt;</a>
</div>
<h4>Sample Code</h4>
<div>
<pre>#include &lt;<a href="../headers/facilities/overload.html">boost/preprocessor/facilities/overload.hpp</a>&gt;<br>#include <<a
href="../headers/cat.html">boost/preprocessor/cat.hpp</a>><br>#include <<a href="../headers/facilities/empty.html">boost/preprocessor/facilities/empty.hpp</a>><br>#include <<a
href="../headers/arithmetic/add.html">boost/preprocessor/arithmetic/add.hpp</a>><br><br>#define MACRO_1(number) MACRO_2(number,10)<br>#define MACRO_2(number1,number2) <a
href="add.html">BOOST_PP_ADD</a>(number1,number2)<br><br>#if !BOOST_PP_VARIADICS_MSVC<br><br>#define MACRO_ADD_NUMBERS(...) <a
href="overload.html">BOOST_PP_OVERLOAD</a>(MACRO_,__VA_ARGS__)(__VA_ARGS__)<br><br>#else<br><br>// or for Visual C++<br><br>#define MACRO_ADD_NUMBERS(...) \<br> <a
href="cat.html">BOOST_PP_CAT</a>(<a href="overload.html">BOOST_PP_OVERLOAD</a>(MACRO_,__VA_ARGS__)(__VA_ARGS__),<a
href="empty.html">BOOST_PP_EMPTY</a>())<br><br>#endif<br><br>MACRO_ADD_NUMBERS(5) // output is 15<br>MACRO_ADD_NUMBERS(3,6) // output is 9</pre>
</div>
<hr size="1">
<div style="margin-left: 0px;"> <i></i><i><EFBFBD> Copyright Edward Diener 2011,2013,2016</i> </div>
<div style="margin-left: 0px;">
<p><small>Distributed under the Boost Software License, Version 1.0.
(See accompanying file <a href="../../../../LICENSE_1_0.txt">LICENSE_1_0.txt</a>
or copy at <a href="http://www.boost.org/LICENSE_1_0.txt">www.boost.org/LICENSE_1_0.txt</a>)</small></p>
</div>
</body></html>