<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> <title>Class template param</title> <link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css"> <meta name="generator" content="DocBook XSL Stylesheets V1.78.1"> <link rel="home" href="../../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> <link rel="up" href="../../boost_typeerasure/reference.html#header.boost.type_erasure.param_hpp" title="Header <boost/type_erasure/param.hpp>"> <link rel="prev" href="binding.html" title="Class template binding"> <link rel="next" href="_a.html" title="Struct _a"> </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 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class="refentrytitle">Class template param</span></h2> <p>boost::type_erasure::param — A wrapper to help with overload resolution for functions operating on an <a class="link" href="any.html" title="Class template any">any</a>. </p> </div> <h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> <div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: <<a class="link" href="../../boost_typeerasure/reference.html#header.boost.type_erasure.param_hpp" title="Header <boost/type_erasure/param.hpp>">boost/type_erasure/param.hpp</a>> </span><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Concept<span class="special">,</span> <span class="keyword">typename</span> T<span class="special">></span> <span class="keyword">class</span> <a class="link" href="param.html" title="Class template param">param</a> <span class="special">{</span> <span class="keyword">public</span><span class="special">:</span> <span class="comment">// <a class="link" href="param.html#boost.type_erasure.paramconstruct-copy-destruct">construct/copy/destruct</a></span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> U<span class="special">></span> <a class="link" href="param.html#idm45506889933952-bb"><span class="identifier">param</span></a><span class="special">(</span><a class="link" href="../any.html" title="Class any">any</a><span class="special"><</span> <span class="identifier">Concept</span><span class="special">,</span> <span class="identifier">U</span> <span class="special">></span> <span class="special">&</span><span class="special">)</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> U<span class="special">></span> <a class="link" href="param.html#idm45506889931840-bb"><span class="identifier">param</span></a><span class="special">(</span><span class="keyword">const</span> <a class="link" href="../any.html" title="Class any">any</a><span class="special"><</span> <span class="identifier">Concept</span><span class="special">,</span> <span class="identifier">U</span> <span class="special">></span> <span class="special">&</span><span class="special">)</span><span class="special">;</span> <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> U<span class="special">></span> <a class="link" href="param.html#idm45506889929568-bb"><span class="identifier">param</span></a><span class="special">(</span><a class="link" href="../any.html" title="Class any">any</a><span class="special"><</span> <span class="identifier">Concept</span><span class="special">,</span> <span class="identifier">U</span> <span class="special">></span> <span class="special">&&</span><span class="special">)</span><span class="special">;</span> <span class="comment">// <a class="link" href="param.html#idm45506889937232-bb">public member functions</a></span> <a class="link" href="../any.html" title="Class any">any</a><span class="special"><</span> <span class="identifier">Concept</span><span class="special">,</span> <span class="identifier">T</span> <span class="special">></span> <a class="link" href="param.html#idm45506889936672-bb"><span class="identifier">get</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span> <span class="special">}</span><span class="special">;</span></pre></div> <div class="refsect1"> <a name="idm45555076336336"></a><h2>Description</h2> <p>The template arguments are interpreted in the same way as <a class="link" href="any.html" title="Class template any">any</a>.</p> <p>A parameter of type <a class="link" href="param.html" title="Class template param">param</a> can be initialized with an <a class="link" href="any.html" title="Class template any">any</a> that has the same <code class="computeroutput">Concept</code> and base placeholder when there exists a corresponding standard conversion for the placeholder. A conversion sequence from any<C, P> to param<C, P1> is a better conversion sequence than any<C, P> to param<C, P2> iff the corresponding placeholder standard conversion sequence from P to P1 is a better conversion sequence than P to P2.</p> <div class="note"><table border="0" summary="Note"> <tr> <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../doc/src/images/note.png"></td> <th align="left">Note</th> </tr> <tr><td align="left" valign="top"><p>Overloading based on cv-qualifiers and rvalue-ness is only supported in C++11. In C++03, all conversion sequences from <a class="link" href="any.html" title="Class template any">any</a> to <a class="link" href="param.html" title="Class template param">param</a> have the same rank.</p></td></tr> </table></div> <p> Example:</p> <pre class="programlisting"><span class="keyword">void</span> <span class="identifier">f</span><span class="special">(</span><span class="identifier">param</span><span class="special"><</span><span class="identifier">C</span><span class="special">,</span> <span class="identifier">_a</span><span class="special">&</span><span class="special">></span><span class="special">)</span><span class="special">;</span> <span class="keyword">void</span> <span class="identifier">f</span><span class="special">(</span><span class="identifier">param</span><span class="special"><</span><span class="identifier">C</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">_a</span><span class="special">&</span><span class="special">></span><span class="special">)</span><span class="special">;</span> <span class="keyword">void</span> <span class="identifier">g</span><span class="special">(</span><span class="identifier">param</span><span class="special"><</span><span class="identifier">C</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">_a</span><span class="special">&</span><span class="special">></span><span class="special">)</span><span class="special">;</span> <span class="keyword">void</span> <span class="identifier">g</span><span class="special">(</span><span class="identifier">param</span><span class="special"><</span><span class="identifier">C</span><span class="special">,</span> <span class="identifier">_a</span><span class="special">&&</span><span class="special">></span><span class="special">)</span><span class="special">;</span> <span class="identifier">any</span><span class="special"><</span><span class="identifier">C</span><span class="special">,</span> <span class="identifier">_a</span><span class="special">></span> <span class="identifier">a</span><span class="special">;</span> <span class="identifier">f</span><span class="special">(</span><span class="identifier">any</span><span class="special"><</span><span class="identifier">C</span><span class="special">,</span> <span class="identifier">_a</span><span class="special">></span><span class="special">(</span><span class="special">)</span><span class="special">)</span><span class="special">;</span> <span class="comment">// calls void f(param<C, const _a&>);</span> <span class="identifier">f</span><span class="special">(</span><span class="identifier">a</span><span class="special">)</span><span class="special">;</span> <span class="comment">// calls void f(param<C, _a&>); (ambiguous in C++03)</span> <span class="identifier">g</span><span class="special">(</span><span class="identifier">any</span><span class="special"><</span><span class="identifier">C</span><span class="special">,</span> <span class="identifier">_a</span><span class="special">></span><span class="special">(</span><span class="special">)</span><span class="special">)</span><span class="special">;</span> <span class="comment">// calls void g(param<C, _a&&>); (ambiguous in C++03)</span> <span class="identifier">g</span><span class="special">(</span><span class="identifier">a</span><span class="special">)</span><span class="special">;</span> <span class="comment">// calls void g(param<C, const _a&>);</span> </pre> <p> </p> <div class="refsect2"> <a name="idm45555076272768"></a><h3> <a name="boost.type_erasure.paramconstruct-copy-destruct"></a><code class="computeroutput">param</code> public construct/copy/destruct</h3> <div class="orderedlist"><ol class="orderedlist" type="1"> <li class="listitem"><pre class="literallayout"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> U<span class="special">></span> <a name="idm45506889933952-bb"></a><span class="identifier">param</span><span class="special">(</span><a class="link" href="../any.html" title="Class any">any</a><span class="special"><</span> <span class="identifier">Concept</span><span class="special">,</span> <span class="identifier">U</span> <span class="special">></span> <span class="special">&</span> a<span class="special">)</span><span class="special">;</span></pre></li> <li class="listitem"><pre class="literallayout"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> U<span class="special">></span> <a name="idm45506889931840-bb"></a><span class="identifier">param</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="../any.html" title="Class any">any</a><span class="special"><</span> <span class="identifier">Concept</span><span class="special">,</span> <span class="identifier">U</span> <span class="special">></span> <span class="special">&</span> a<span class="special">)</span><span class="special">;</span></pre></li> <li class="listitem"><pre class="literallayout"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> U<span class="special">></span> <a name="idm45506889929568-bb"></a><span class="identifier">param</span><span class="special">(</span><a class="link" href="../any.html" title="Class any">any</a><span class="special"><</span> <span class="identifier">Concept</span><span class="special">,</span> <span class="identifier">U</span> <span class="special">></span> <span class="special">&&</span> a<span class="special">)</span><span class="special">;</span></pre></li> </ol></div> </div> <div class="refsect2"> <a name="idm45555076237728"></a><h3> <a name="idm45506889937232-bb"></a><code class="computeroutput">param</code> public member functions</h3> <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"> <pre class="literallayout"><a class="link" href="../any.html" title="Class any">any</a><span class="special"><</span> <span class="identifier">Concept</span><span class="special">,</span> <span class="identifier">T</span> <span class="special">></span> <a name="idm45506889936672-bb"></a><span class="identifier">get</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre> <p>Returns the stored <code class="computeroutput"><a class="link" href="any.html" title="Class template any">any</a></code>. </p> </li></ol></div> </div> </div> </div> <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> <td align="left"></td> <td align="right"><div class="copyright-footer">Copyright © 2011-2013 Steven Watanabe<p> 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>) </p> </div></td> </tr></table> <hr> <div class="spirit-nav"> <a accesskey="p" href="binding.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../boost_typeerasure/reference.html#header.boost.type_erasure.param_hpp"><img src="../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="_a.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> </div> </body> </html>