1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<head> 4<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 5<title>Class template param</title> 6<link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css"> 7<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 8<link rel="home" href="../../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> 9<link rel="up" href="../../boost_typeerasure/reference.html#header.boost.type_erasure.param_hpp" title="Header <boost/type_erasure/param.hpp>"> 10<link rel="prev" href="as_param.html" title="Struct template as_param"> 11<link rel="next" href="_a.html" title="Struct _a"> 12</head> 13<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 14<table cellpadding="2" width="100%"><tr> 15<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../boost.png"></td> 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28<div class="refnamediv"> 29<h2><span class="refentrytitle">Class template param</span></h2> 30<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> 31</div> 32<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> 33<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>> 34 35</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> 36<span class="keyword">class</span> <a class="link" href="param.html" title="Class template param">param</a> <span class="special">{</span> 37<span class="keyword">public</span><span class="special">:</span> 38 <span class="comment">// <a class="link" href="param.html#boost.type_erasure.paramconstruct-copy-destruct">construct/copy/destruct</a></span> 39 <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#id-1_3_41_13_25_1_1_2_5-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> 40 <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#id-1_3_41_13_25_1_1_2_6-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> 41 <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#id-1_3_41_13_25_1_1_2_7-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> 42 43 <span class="comment">// <a class="link" href="param.html#id-1_3_41_13_25_1_1_2_4-bb">public member functions</a></span> 44 <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#id-1_3_41_13_25_1_1_2_4_1-bb"><span class="identifier">get</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span> 45<span class="special">}</span><span class="special">;</span></pre></div> 46<div class="refsect1"> 47<a name="id-1.3.41.13.26.4.4"></a><h2>Description</h2> 48<p>The template arguments are interpreted in the same way as <a class="link" href="any.html" title="Class template any">any</a>.</p> 49<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 <a class="link" href="any.html" title="Class template any">any<C, P></a> to <a class="link" href="param.html" title="Class template param">param<C, P1></a> is a better conversion sequence than <a class="link" href="any.html" title="Class template any">any<C, P></a> to <a class="link" href="param.html" title="Class template param">param<C, P2></a> iff the corresponding placeholder standard conversion sequence from P to P1 is a better conversion sequence than P to P2.</p> 50<div class="note"><table border="0" summary="Note"> 51<tr> 52<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../doc/src/images/note.png"></td> 53<th align="left">Note</th> 54</tr> 55<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> 56</table></div> 57<p> 58Example:</p> 59<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> 60<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> 61<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> 62<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> 63 64<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> 65<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> 66<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> 67<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> 68<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> 69</pre> 70<p> </p> 71<div class="refsect2"> 72<a name="id-1.3.41.13.26.4.4.6"></a><h3> 73<a name="boost.type_erasure.paramconstruct-copy-destruct"></a><code class="computeroutput">param</code> 74 public 75 construct/copy/destruct</h3> 76<div class="orderedlist"><ol class="orderedlist" type="1"> 77<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="id-1_3_41_13_25_1_1_2_5-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> 78<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="id-1_3_41_13_25_1_1_2_6-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> 79<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="id-1_3_41_13_25_1_1_2_7-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> 80</ol></div> 81</div> 82<div class="refsect2"> 83<a name="id-1.3.41.13.26.4.4.7"></a><h3> 84<a name="id-1_3_41_13_25_1_1_2_4-bb"></a><code class="computeroutput">param</code> public member functions</h3> 85<div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"> 86<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="id-1_3_41_13_25_1_1_2_4_1-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> 87<p>Returns the stored <code class="computeroutput"><a class="link" href="any.html" title="Class template any">any</a></code>. </p> 88</li></ol></div> 89</div> 90</div> 91</div> 92<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 93<td align="left"></td> 94<td align="right"><div class="copyright-footer">Copyright © 2011-2013 Steven Watanabe<p> 95 Distributed under the Boost Software License, Version 1.0. (See accompanying 96 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>) 97 </p> 98</div></td> 99</tr></table> 100<hr> 101<div class="spirit-nav"> 102<a accesskey="p" href="as_param.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> 103</div> 104</body> 105</html> 106
