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<title>The Boost Parameter Library Reference Documentation</title>
<meta name="authors" content="David Abrahams Daniel Wallin" />
<meta name="organization" content="Boost Consulting" />
<meta name="date" content="2005-07-17" />
<meta name="copyright" content="Copyright David Abrahams, Daniel Wallin 2005. Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)" />
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</head>
<body>
<div class="document" id="the-boost-parameter-library-reference-documentation">
<h1 class="title">The Boost Parameter Library Reference Documentation</h1>
<table class="docinfo" frame="void" rules="none">
<col class="docinfo-name" />
<col class="docinfo-content" />
<tbody valign="top">
<tr><th class="docinfo-name">Authors:</th>
<td>David Abrahams
<br />Daniel Wallin</td></tr>
<tr><th class="docinfo-name">Contact:</th>
<td><a class="first reference" href="mailto:dave@boost-consulting.com">dave@boost-consulting.com</a>, <a class="last reference" href="mailto:dalwan01@student.umu.se">dalwan01@student.umu.se</a></td></tr>
<tr><th class="docinfo-name">Organization:</th>
<td><a class="first last reference" href="http://www.boost-consulting.com">Boost Consulting</a></td></tr>
<tr><th class="docinfo-name">Date:</th>
<td>2005-07-17</td></tr>
<tr><th class="docinfo-name">Copyright:</th>
<td>Copyright David Abrahams, Daniel Wallin
2005. Distributed under the Boost Software License,
Version 1.0. (See accompanying file LICENSE_1_0.txt
or copy at <a class="reference" href="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</a>)</td></tr>
</tbody>
</table>
<p><a class="reference" href="../../../../index.htm"><img alt="Boost" src="../../../../boost.png" /></a></p>
<hr class="docutils" />
<div class="contents topic">
<p class="topic-title first"><a id="contents" name="contents">Contents</a></p>
<ul class="auto-toc simple">
<li><a class="reference" href="#preliminaries" id="id30" name="id30">1 Preliminaries</a><ul class="auto-toc">
<li><a class="reference" href="#namespaces" id="id31" name="id31">1.1 Namespaces</a></li>
<li><a class="reference" href="#exceptions" id="id32" name="id32">1.2 Exceptions</a></li>
<li><a class="reference" href="#thread-safety" id="id33" name="id33">1.3 Thread Safety</a></li>
<li><a class="reference" href="#typography" id="id34" name="id34">1.4 Typography</a></li>
</ul>
</li>
<li><a class="reference" href="#terminology" id="id35" name="id35">2 Terminology</a></li>
<li><a class="reference" href="#concepts" id="id36" name="id36">3 Concepts</a><ul class="auto-toc">
<li><a class="reference" href="#argumentpack" id="id37" name="id37">3.1 <span class="concept">ArgumentPack</span></a></li>
<li><a class="reference" href="#id5" id="id38" name="id38">3.2 <span class="concept">ParameterSpec</span></a></li>
</ul>
</li>
<li><a class="reference" href="#class-templates" id="id39" name="id39">4 Class Templates</a><ul class="auto-toc">
<li><a class="reference" href="#id7" id="id40" name="id40">4.1 <tt class="docutils literal"><span class="pre">keyword</span></tt></a></li>
<li><a class="reference" href="#parameters" id="id41" name="id41">4.2 <tt class="docutils literal"><span class="pre">parameters</span></tt></a></li>
<li><a class="reference" href="#optional-required" id="id42" name="id42">4.3 <tt class="docutils literal"><span class="pre">optional</span></tt>, <tt class="docutils literal"><span class="pre">required</span></tt></a></li>
<li><a class="reference" href="#deduced" id="id43" name="id43">4.4 <tt class="docutils literal"><span class="pre">deduced</span></tt></a></li>
</ul>
</li>
<li><a class="reference" href="#metafunctions" id="id44" name="id44">5 Metafunctions</a><ul class="auto-toc">
<li><a class="reference" href="#binding" id="id45" name="id45">5.1 <tt class="docutils literal"><span class="pre">binding</span></tt></a></li>
<li><a class="reference" href="#lazy-binding" id="id46" name="id46">5.2 <tt class="docutils literal"><span class="pre">lazy_binding</span></tt></a></li>
<li><a class="reference" href="#value-type" id="id47" name="id47">5.3 <tt class="docutils literal"><span class="pre">value_type</span></tt></a></li>
</ul>
</li>
<li><a class="reference" href="#code-generation-macros" id="id48" name="id48">6 Code Generation Macros</a><ul class="auto-toc">
<li><a class="reference" href="#boost-parameter-function-result-name-tag-namespace-arguments" id="id49" name="id49">6.1 <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_FUNCTION(result,name,tag_namespace,arguments)</span></tt></a></li>
<li><a class="reference" href="#boost-parameter-member-function-result-name-tag-namespace-arguments" id="id50" name="id50">6.2 <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_MEMBER_FUNCTION(result,name,tag_namespace,arguments)</span></tt></a></li>
<li><a class="reference" href="#boost-parameter-constructor-cls-impl-tag-namespace-arguments" id="id51" name="id51">6.3 <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_CONSTRUCTOR(cls,</span> <span class="pre">impl,</span> <span class="pre">tag_namespace,</span> <span class="pre">arguments)</span></tt></a></li>
<li><a class="reference" href="#boost-parameter-name-name" id="id52" name="id52">6.4 <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_NAME(name)</span></tt></a></li>
<li><a class="reference" href="#boost-parameter-template-keyword-name" id="id53" name="id53">6.5 <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_TEMPLATE_KEYWORD(name)</span></tt></a></li>
<li><a class="reference" href="#boost-parameter-fun-r-n-l-h-p" id="id54" name="id54">6.6 <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_FUN(r,n,l,h,p)</span></tt></a></li>
<li><a class="reference" href="#boost-parameter-keyword-n-k" id="id55" name="id55">6.7 <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_KEYWORD(n,k)</span></tt></a></li>
<li><a class="reference" href="#boost-parameter-match-p-a-x" id="id56" name="id56">6.8 <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_MATCH(p,a,x)</span></tt></a></li>
</ul>
</li>
<li><a class="reference" href="#configuration-macros" id="id57" name="id57">7 Configuration Macros</a><ul class="auto-toc">
<li><a class="reference" href="#boost-parameter-max-arity" id="id58" name="id58">7.1 <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_MAX_ARITY</span></tt></a></li>
</ul>
</li>
<li><a class="reference" href="#tutorial" id="id59" name="id59">8 Tutorial</a></li>
</ul>
</div>
<hr class="docutils" />
<div class="section">
<h1><a class="toc-backref" href="#id30" id="preliminaries" name="preliminaries">1 Preliminaries</a></h1>
<p>This section covers some basic information you'll need to know in
order to understand this reference</p>
<div class="section">
<h2><a class="toc-backref" href="#id31" id="namespaces" name="namespaces">1.1 Namespaces</a></h2>
<p>In this document, all unqualified identifiers should be assumed to
be defined in namespace <tt class="docutils literal"><span class="pre">boost::parameter</span></tt> unless otherwise
specified.</p>
</div>
<div class="section">
<h2><a class="toc-backref" href="#id32" id="exceptions" name="exceptions">1.2 Exceptions</a></h2>
<p>No operation described in this document
throws an exception unless otherwise specified.</p>
</div>
<div class="section">
<h2><a class="toc-backref" href="#id33" id="thread-safety" name="thread-safety">1.3 Thread Safety</a></h2>
<p>All components of this library can be used safely from multiple
threads without synchronization.<a class="footnote-reference" href="#thread" id="id2" name="id2"><sup>1</sup></a></p>
</div>
<div class="section">
<h2><a class="toc-backref" href="#id34" id="typography" name="typography">1.4 Typography</a></h2>
<p>Names written in <span class="concept">sans serif type</span> represent <a class="reference" href="../../../../more/generic_programming.html#concept">concepts</a>.</p>
<p>In code blocks, <em>italic type</em> represents unspecified text that
satisfies the requirements given in the detailed description that
follows the code block.</p>
<p>In a specification of the tokens generated by a macro, <strong>bold
type</strong> is used to highlight the position of the expanded macro
argument in the result.</p>
<p>The special character β represents the value of <a class="reference" href="#boost-parameter-max-arity"><tt class="docutils literal"><span class="pre">BOOST_PARAMETER_MAX_ARITY</span></tt></a>.</p>
</div>
</div>
<hr class="docutils" />
<div class="section">
<h1><a class="toc-backref" href="#id35" id="terminology" name="terminology">2 Terminology</a></h1>
<dl class="docutils" id="kw">
<dt>keyword</dt>
<dd>The name of a function parameter.</dd>
</dl>
<span class="target" id="keyword-tag-type"></span><dl class="docutils">
<dt>keyword tag type</dt>
<dd>A type used to uniquely identify a function parameter. Typically
its name will be the same as that of the parameter.</dd>
</dl>
<span class="target" id="positional"></span><dl class="docutils">
<dt>positional argument</dt>
<dd>An argument passed with no explicit keyword. Its parameter is
determined in the usual C++ way: by position with respect to a
parameter list.</dd>
</dl>
<span class="target" id="tag-type"></span><dl class="docutils">
<dt>tag type</dt>
<dd>Shorthand for “<a class="reference" href="#keyword-tag-type">keyword tag type</a>.”</dd>
</dl>
<span class="target" id="keyword-object"></span><dl class="docutils">
<dt>keyword object</dt>
<dd>An instance of <a class="reference" href="#keyword"><tt class="docutils literal"><span class="pre">keyword</span></tt></a> <tt class="docutils literal"><span class="pre"><T></span></tt> for some <a class="reference" href="#tag-type">tag type</a> <tt class="docutils literal"><span class="pre">T</span></tt>.</dd>
</dl>
<span class="target" id="tagged-reference"></span><dl class="docutils">
<dt>tagged reference</dt>
<dd><p class="first">An object whose type is associated with a <a class="reference" href="#keyword-tag-type">keyword tag type</a> (the
object's <em>keyword</em>), and that holds a reference (to the object's
<em>value</em>).</p>
<p class="last">As a shorthand, a “tagged reference to <tt class="docutils literal"><span class="pre">x</span></tt>” means a tagged
reference whose <em>value</em> is <tt class="docutils literal"><span class="pre">x</span></tt>.</p>
</dd>
</dl>
<span class="target" id="tagged-default"></span><dl class="docutils">
<dt>tagged default</dt>
<dd>A <a class="reference" href="#tagged-reference">tagged reference</a> whose <em>value</em> represents the value of a
default argument.</dd>
</dl>
<span class="target" id="tagged-lazy-default"></span><dl class="docutils">
<dt>tagged lazy default</dt>
<dd>A <a class="reference" href="#tagged-reference">tagged reference</a> whose <em>value</em>, when invoked with no
arguments, computes a default argument value.</dd>
</dl>
<span class="target" id="intended-argument-type"></span><dl class="docutils">
<dt>intended argument type</dt>
<dd>The <em>intended argument type</em> of a single-element <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> is the
type of its element's <em>value</em>. The intended argument type of any other
type <tt class="docutils literal"><span class="pre">X</span></tt> is <tt class="docutils literal"><span class="pre">X</span></tt> itself.</dd>
</dl>
<div class="note">
<p class="first admonition-title">Note</p>
<p class="last">In this reference, we will use concept names (and other names)
to describe both types and objects, depending on context. So
for example, “an <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a>” can refer to a type that
models <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> <em>or</em> an object of such a type.</p>
</div>
</div>
<hr class="docutils" />
<div class="section">
<h1><a class="toc-backref" href="#id36" id="concepts" name="concepts">3 Concepts</a></h1>
<p>This section describes the generic type <a class="reference" href="../../../../more/generic_programming.html#concept">concepts</a> used by the Parameter library.</p>
<div class="section">
<h2><a class="toc-backref" href="#id37" id="argumentpack" name="argumentpack">3.1 <span class="concept">ArgumentPack</span></a></h2>
<p>An <span class="concept">ArgumentPack</span> is a collection of <a class="reference" href="#tagged-reference">tagged reference</a>s to the
actual arguments passed to a function. Every <span class="concept">ArgumentPack</span> is
also a valid MPL <a class="reference" href="../../../mpl/doc/refmanual/forward-sequence.html"><span class="concept">Forward Sequence</span></a> consisting of the <a class="reference" href="#keyword-tag-type">keyword tag type</a>s in its <a class="reference" href="#tagged-reference">tagged reference</a>s.</p>
<div class="section">
<h3><a id="requirements" name="requirements">Requirements</a></h3>
<p>In the table below,</p>
<ul class="simple">
<li><tt class="docutils literal"><span class="pre">A</span></tt> is a model of <span class="concept">ArgumentPack</span></li>
<li><tt class="docutils literal"><span class="pre">x</span></tt> is an instance of <tt class="docutils literal"><span class="pre">A</span></tt></li>
<li><tt class="docutils literal"><span class="pre">u</span></tt> is a <a class="reference" href="#keyword-object">keyword object</a> of type <tt class="docutils literal"><span class="pre">K</span></tt></li>
<li><tt class="docutils literal"><span class="pre">v</span></tt> is a <a class="reference" href="#tagged-default">tagged default</a> with <a class="reference" href="#tag-type">tag type</a> <tt class="docutils literal"><span class="pre">L</span></tt> and <em>value</em> of type <tt class="docutils literal"><span class="pre">D</span></tt></li>
<li><tt class="docutils literal"><span class="pre">w</span></tt> is a <a class="reference" href="#tagged-lazy-default">tagged lazy default</a> with <a class="reference" href="#tag-type">tag type</a> <tt class="docutils literal"><span class="pre">M</span></tt> and <em>value</em> of type <tt class="docutils literal"><span class="pre">E</span> <span class="pre">const</span></tt></li>
<li><tt class="docutils literal"><span class="pre">z</span></tt> is an <span class="concept">ArgumentPack</span> containing a single element (as created by <a class="reference" href="#keyword"><tt class="docutils literal"><span class="pre">keyword</span></tt></a><tt class="docutils literal"><span class="pre"><…>::operator=</span></tt>)</li>
</ul>
<p>Any exceptions are thrown from the invocation of <tt class="docutils literal"><span class="pre">w</span></tt>'s <em>value</em>
will be propagated to the caller.</p>
<table border="1" class="docutils">
<caption><span class="concept">ArgumentPack</span> requirements</caption>
<colgroup>
<col width="11%" />
<col width="31%" />
<col width="19%" />
<col width="40%" />
</colgroup>
<thead valign="bottom">
<tr><th class="head">Expression</th>
<th class="head">Type</th>
<th class="head">Requirements</th>
<th class="head">Semantics/Notes</th>
</tr>
</thead>
<tbody valign="top">
<tr><td><tt class="docutils literal"><span class="pre">x[u]</span></tt></td>
<td><tt class="docutils literal"><span class="pre">binding<A,K>::type</span></tt></td>
<td><tt class="docutils literal"><span class="pre">x</span></tt> contains an
element <em>b</em> whose
<a class="reference" href="#kw">keyword</a> is <tt class="docutils literal"><span class="pre">K</span></tt></td>
<td>Returns <em>b</em>'s <em>value</em> (by
reference).</td>
</tr>
<tr><td><tt class="docutils literal"><span class="pre">x[u]</span></tt></td>
<td><tt class="docutils literal"><span class="pre">binding<A,L,D>::type</span></tt></td>
<td><em>none</em></td>
<td>If <tt class="docutils literal"><span class="pre">x</span></tt> contains an element <em>b</em> whose
<a class="reference" href="#kw">keyword</a> is the same as <tt class="docutils literal"><span class="pre">u</span></tt>'s,
returns <em>b</em>'s <em>value</em> (by
reference). Otherwise, returns <tt class="docutils literal"><span class="pre">u</span></tt>'s <em>value</em>.</td>
</tr>
<tr><td><tt class="docutils literal"><span class="pre">x[w]</span></tt></td>
<td><tt class="docutils literal"><span class="pre">lazy_binding<A,M,E>::type</span></tt></td>
<td><em>none</em></td>
<td>If <tt class="docutils literal"><span class="pre">x</span></tt> contains an element <em>b</em> whose
<a class="reference" href="#kw">keyword</a> is the same as <tt class="docutils literal"><span class="pre">w</span></tt>'s,
returns <em>b</em>'s <em>value</em> (by
reference). Otherwise, invokes <tt class="docutils literal"><span class="pre">w</span></tt>'s <em>value</em> and returns the result.</td>
</tr>
<tr><td><tt class="docutils literal"><span class="pre">x,</span> <span class="pre">z</span></tt></td>
<td>Model of <span class="concept">ArgumentPack</span></td>
<td><em>none</em></td>
<td>Returns an <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> containing
all the elements of both <tt class="docutils literal"><span class="pre">x</span></tt> and
<tt class="docutils literal"><span class="pre">z</span></tt>.</td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="section">
<h2><a class="toc-backref" href="#id38" id="id5" name="id5"><span id="parameterspec"></span>3.2 <span class="concept">ParameterSpec</span></a></h2>
<p>A <span class="concept">ParameterSpec</span> describes the type requirements for arguments
corresponding to a given <a class="reference" href="#kw">keyword</a> and indicates whether the argument
is optional or required. The table below details the allowed forms
and describes their condition for satisfaction by an actual
argument type. In each row,</p>
<ul class="simple" id="conditions">
<li><tt class="docutils literal"><span class="pre">K</span></tt> is the <span class="concept">ParameterSpec</span>'s <a class="reference" href="#keyword-tag-type">keyword tag type</a></li>
<li><tt class="docutils literal"><span class="pre">A</span></tt> is an <a class="reference" href="#intended-argument-type">intended argument type</a> associated with <tt class="docutils literal"><span class="pre">K</span></tt>, if any</li>
<li><tt class="docutils literal"><span class="pre">F</span></tt> is a unary <a class="reference" href="../../../mpl/doc/refmanual/lambda-expression.html">MPL lambda expression</a></li>
</ul>
<table border="1" class="docutils">
<caption><span class="concept">ParameterSpec</span> allowed forms and conditions of satisfaction</caption>
<colgroup>
<col width="32%" />
<col width="21%" />
<col width="47%" />
</colgroup>
<thead valign="bottom">
<tr><th class="head">Type</th>
<th class="head"><tt class="docutils literal"><span class="pre">A</span></tt> required</th>
<th class="head">Condition <tt class="docutils literal"><span class="pre">A</span></tt> must satisfy</th>
</tr>
</thead>
<tbody valign="top">
<tr><td><tt class="docutils literal"><span class="pre">K</span></tt></td>
<td>no</td>
<td><em>n/a</em></td>
</tr>
<tr><td><a class="reference" href="#optional"><tt class="docutils literal"><span class="pre">optional</span></tt></a><tt class="docutils literal"><span class="pre"><K,F></span></tt></td>
<td>no</td>
<td><tt class="docutils literal"><span class="pre">mpl::apply<F,A>::type::value</span></tt>
is <tt class="docutils literal"><span class="pre">true</span></tt>.</td>
</tr>
<tr><td><a class="reference" href="#required"><tt class="docutils literal"><span class="pre">required</span></tt></a><tt class="docutils literal"><span class="pre"><K,F></span></tt></td>
<td>yes</td>
<td><tt class="docutils literal"><span class="pre">mpl::apply<F,A>::type::value</span></tt>
is <tt class="docutils literal"><span class="pre">true</span></tt>.</td>
</tr>
</tbody>
</table>
<p>The information in a <span class="concept">ParameterSpec</span> is used to <a class="reference" href="index.html#controlling-overload-resolution">limit</a> the
arguments that will be matched by <a class="reference" href="index.html#forwarding-functions">forwarding functions</a>.</p>
</div>
</div>
<hr class="docutils" />
<div class="section">
<h1><a class="toc-backref" href="#id39" id="class-templates" name="class-templates">4 Class Templates</a></h1>
<div class="section">
<h2><a class="toc-backref" href="#id40" id="id7" name="id7"><span id="keyword"></span>4.1 <tt class="docutils literal"><span class="pre">keyword</span></tt></a></h2>
<p>The type of every <a class="reference" href="#keyword-object">keyword object</a> is a specialization of <tt class="docutils literal"><span class="pre">keyword</span></tt>.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/keyword.hpp">boost/parameter/keyword.hpp</a></td>
</tr>
</tbody>
</table>
<pre class="literal-block">
template <class Tag>
struct keyword
{
template <class T> <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> <a class="reference" href="#operator">operator=</a>(T& value) const;
template <class T> <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> <a class="reference" href="#operator">operator=</a>(T const& value) const;
template <class T> <em>tagged default</em> <a class="reference" href="#id9">operator|</a>(T& x) const;
template <class T> <em>tagged default</em> <a class="reference" href="#id9">operator|</a>(T const& x) const;
template <class F> <em>tagged lazy default</em> <a class="reference" href="#id10">operator||</a>(F const&) const;
static keyword<Tag>& <a class="reference" href="#get">get</a>();
};
</pre>
<dl class="docutils" id="operator">
<dt><tt class="docutils literal"><span class="pre">operator=</span></tt></dt>
<dd><pre class="first literal-block">
template <class T> <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> operator=(T& value) const;
template <class T> <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> operator=(T const& value) const;
</pre>
<table class="last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Requires:</th><td class="field-body">nothing</td>
</tr>
<tr class="field"><th class="field-name">Returns:</th><td class="field-body">an <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> containing a single <a class="reference" href="#tagged-reference">tagged reference</a> to
<tt class="docutils literal"><span class="pre">value</span></tt> with <a class="reference" href="#kw">keyword</a> <tt class="docutils literal"><span class="pre">Tag</span></tt></td>
</tr>
</tbody>
</table>
</dd>
</dl>
<dl class="docutils" id="id9">
<dt><tt class="docutils literal"><span class="pre">operator|</span></tt></dt>
<dd><pre class="first literal-block">
template <class T> <em>tagged default</em> operator|(T& x) const;
template <class T> <em>tagged default</em> operator|(T const& x) const;
</pre>
<table class="last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Returns:</th><td class="field-body">a <a class="reference" href="#tagged-default">tagged default</a> with <em>value</em> <tt class="docutils literal"><span class="pre">x</span></tt> and <a class="reference" href="#kw">keyword</a> <tt class="docutils literal"><span class="pre">Tag</span></tt>.</td>
</tr>
</tbody>
</table>
</dd>
</dl>
<dl class="docutils" id="id10">
<dt><tt class="docutils literal"><span class="pre">operator||</span></tt></dt>
<dd><pre class="first literal-block">
template <class F> <em>tagged lazy default</em> operator||(F const& g) const;
</pre>
<table class="last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><tt class="docutils literal"><span class="pre">g()</span></tt> is valid, with type <tt class="docutils literal"><span class="pre">boost::</span></tt><a class="reference" href="../../../utility/utility.htm#result_of"><tt class="docutils literal"><span class="pre">result_of</span></tt></a><tt class="docutils literal"><span class="pre"><F()>::type</span></tt>.<a class="footnote-reference" href="#no-result-of" id="id11" name="id11"><sup>2</sup></a></td>
</tr>
<tr class="field"><th class="field-name">Returns:</th><td class="field-body">a <a class="reference" href="#tagged-lazy-default">tagged lazy default</a> with <em>value</em> <tt class="docutils literal"><span class="pre">g</span></tt> and <a class="reference" href="#kw">keyword</a> <tt class="docutils literal"><span class="pre">Tag</span></tt>.</td>
</tr>
</tbody>
</table>
</dd>
</dl>
<dl class="docutils" id="get">
<dt><tt class="docutils literal"><span class="pre">get</span></tt></dt>
<dd><pre class="first literal-block">
static keyword<Tag>& get();
</pre>
<table class="last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Returns:</th><td class="field-body">a “singleton instance”: the same object will be
returned on each invocation of <tt class="docutils literal"><span class="pre">get()</span></tt>.</td>
</tr>
<tr class="field"><th class="field-name">Thread Safety:</th><td class="field-body"><tt class="docutils literal"><span class="pre">get()</span></tt> can be called from multiple threads
simultaneously.</td>
</tr>
</tbody>
</table>
</dd>
</dl>
</div>
<div class="section">
<h2><a class="toc-backref" href="#id41" id="parameters" name="parameters">4.2 <tt class="docutils literal"><span class="pre">parameters</span></tt></a></h2>
<p>Provides an interface for assembling the actual arguments to a
<cite>forwarding function</cite> into an <span class="concept">ArgumentPack</span>, in which any
<a class="reference" href="#positional">positional</a> arguments will be tagged according to the
corresponding template argument to <tt class="docutils literal"><span class="pre">parameters</span></tt>.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/parameters.hpp">boost/parameter/parameters.hpp</a></td>
</tr>
</tbody>
</table>
<pre class="literal-block">
template <class P0 = <em>unspecified</em>, class P1 = <em>unspecified</em>, …class Pβ = <em>unspecified</em>>
struct parameters
{
template <class A0, class A1 = <em>unspecified</em>, …class Aβ = <em>unspecified</em>>
struct <a class="reference" href="#match">match</a>
{
typedef … type;
};
template <class A0>
<a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> <a class="reference" href="#id13">operator()</a>(A0& a0) const;
template <class A0, class A1>
<a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> <a class="reference" href="#id13">operator()</a>(A0& a0, A1& a1) const;
<span class="vellipsis">⋮</span>
template <class A0, class A1, …class Aβ>
<a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> <a class="reference" href="#id13">operator()</a>(A0& a0, A1& a1, …Aβ& aβ) const;
};
</pre>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><tt class="docutils literal"><span class="pre">P0</span></tt>, <tt class="docutils literal"><span class="pre">P1</span></tt>, … <tt class="docutils literal"><span class="pre">P</span></tt>β are models of <a class="reference" href="#parameterspec"><span class="concept">ParameterSpec</span></a>.</td>
</tr>
</tbody>
</table>
<div class="note">
<p class="first admonition-title">Note</p>
<p>In this section, <tt class="docutils literal"><span class="pre">R</span></tt><em>i</em> and <tt class="docutils literal"><span class="pre">K</span></tt><em>i</em> are defined as
follows, for any argument type <tt class="docutils literal"><span class="pre">A</span></tt><em>i</em>:</p>
<blockquote class="last">
<div class="line-block">
<div class="line">let <tt class="docutils literal"><span class="pre">D0</span></tt> the set [d0, …, d<em>j</em>] of all <strong>deduced</strong> <em>parameter specs</em> in [<tt class="docutils literal"><span class="pre">P0</span></tt>, …, <tt class="docutils literal"><span class="pre">P</span></tt>β]</div>
<div class="line"><tt class="docutils literal"><span class="pre">R</span></tt><em>i</em> is <tt class="docutils literal"><span class="pre">A</span></tt><em>i</em>'s <a class="reference" href="#intended-argument-type">intended argument type</a></div>
<div class="line"><br /></div>
<div class="line">if <tt class="docutils literal"><span class="pre">A</span></tt><em>i</em> is a result type of <tt class="docutils literal"><span class="pre">keyword<T>::</span></tt><a class="reference" href="#operator"><tt class="docutils literal"><span class="pre">operator=</span></tt></a></div>
<div class="line">then</div>
<div class="line-block">
<div class="line"><tt class="docutils literal"><span class="pre">K</span></tt><em>i</em> is <tt class="docutils literal"><span class="pre">T</span></tt></div>
</div>
<div class="line">else</div>
<div class="line-block">
<div class="line">if some <tt class="docutils literal"><span class="pre">A</span></tt><em>j</em> where <em>j</em>≤<em>i</em> is a result type of <tt class="docutils literal"><span class="pre">keyword<T>::</span></tt><a class="reference" href="#operator"><tt class="docutils literal"><span class="pre">operator=</span></tt></a></div>
<div class="line"><em>or</em> some <tt class="docutils literal"><span class="pre">P</span></tt><em>j</em> in <em>j</em>≤<em>i</em> is <strong>deduced</strong></div>
<div class="line">then</div>
<div class="line-block">
<div class="line">if some <em>parameter spec</em> <tt class="docutils literal"><span class="pre">d</span></tt><em>j</em> in <tt class="docutils literal"><span class="pre">D</span></tt><em>i</em> matches <tt class="docutils literal"><span class="pre">A</span></tt><em>i</em></div>
<div class="line">then</div>
<div class="line-block">
<div class="line"><tt class="docutils literal"><span class="pre">K</span></tt><em>i</em> is <tt class="docutils literal"><span class="pre">d</span></tt><em>j</em>'s <a class="reference" href="#keyword-tag-type">keyword tag type</a>.</div>
<div class="line"><tt class="docutils literal"><span class="pre">D</span></tt><sub>i+1</sub> is <tt class="docutils literal"><span class="pre">D</span></tt><em>i</em> - [<tt class="docutils literal"><span class="pre">d</span></tt><em>j</em>]</div>
</div>
</div>
<div class="line">else</div>
<div class="line-block">
<div class="line"><tt class="docutils literal"><span class="pre">K</span></tt><em>i</em> is <tt class="docutils literal"><span class="pre">P</span></tt><em>i</em>'s <a class="reference" href="#keyword-tag-type">keyword tag type</a>.</div>
</div>
</div>
</div>
</blockquote>
</div>
<dl class="docutils" id="match">
<dt><tt class="docutils literal"><span class="pre">match</span></tt></dt>
<dd><p class="first">A <a class="reference" href="../../../mpl/doc/refmanual/metafunction.html"><span class="concept">Metafunction</span></a> used to remove a <a class="reference" href="index.html#forwarding-functions">forwarding function</a> from overload resolution.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Returns:</th><td class="field-body">if <tt class="docutils literal"><span class="pre">P0</span></tt>, <tt class="docutils literal"><span class="pre">P1</span></tt>, …<tt class="docutils literal"><span class="pre">P</span></tt>β are <em>satisfied</em> (see
below), then <tt class="docutils literal"><span class="pre">parameters<P0,P1,…Pβ></span></tt>. Otherwise,
<tt class="docutils literal"><span class="pre">match<A0,A1,…Aβ>::type</span></tt> is not defined.</td>
</tr>
</tbody>
</table>
<p><tt class="docutils literal"><span class="pre">P0</span></tt>, <tt class="docutils literal"><span class="pre">P1</span></tt>, …<tt class="docutils literal"><span class="pre">P</span></tt>β are <strong>satisfied</strong> if, for
every <em>j</em> in 0…β, either:</p>
<ul class="last simple">
<li><tt class="docutils literal"><span class="pre">P</span></tt><em>j</em> is the <em>unspecified</em> default</li>
<li><strong>or</strong>, <tt class="docutils literal"><span class="pre">P</span></tt><em>j</em> is a <em>keyword tag type</em></li>
<li><strong>or</strong>, <tt class="docutils literal"><span class="pre">P</span></tt><em>j</em> is <a class="reference" href="#optional"><tt class="docutils literal"><span class="pre">optional</span></tt></a> <tt class="docutils literal"><span class="pre"><X,F></span></tt> and either<ul>
<li><tt class="docutils literal"><span class="pre">X</span></tt> is not <tt class="docutils literal"><span class="pre">K</span></tt><em>i</em> for any <em>i</em>,</li>
<li><strong>or</strong> <tt class="docutils literal"><span class="pre">X</span></tt> is some <tt class="docutils literal"><span class="pre">K</span></tt><em>i</em> and <tt class="docutils literal"><span class="pre">mpl::apply<F,R</span></tt><em>i</em><tt class="docutils literal"><span class="pre">>::type::value</span></tt> is <tt class="docutils literal"><span class="pre">true</span></tt></li>
</ul>
</li>
<li><strong>or</strong>, <tt class="docutils literal"><span class="pre">P</span></tt><em>j</em> is <a class="reference" href="#required"><tt class="docutils literal"><span class="pre">required</span></tt></a> <tt class="docutils literal"><span class="pre"><X,F></span></tt>, and<ul>
<li><tt class="docutils literal"><span class="pre">X</span></tt> is some <tt class="docutils literal"><span class="pre">K</span></tt><em>i</em>, <strong>and</strong></li>
<li><tt class="docutils literal"><span class="pre">mpl::apply<F,R</span></tt><em>i</em><tt class="docutils literal"><span class="pre">>::type::value</span></tt> is <tt class="docutils literal"><span class="pre">true</span></tt></li>
</ul>
</li>
</ul>
</dd>
</dl>
<dl class="docutils" id="id13">
<dt><tt class="docutils literal"><span class="pre">operator()</span></tt></dt>
<dd><pre class="first literal-block">
template <class A0> <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> operator()(A0 const& a0) const;
<span class="vellipsis">⋮</span>
template <class A0, …class Aβ> <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> <a class="reference" href="#id13">operator()</a>(A0 const& a0, …Aβ const& aβ) const;
</pre>
<table class="last docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Returns:</th><td class="field-body"><p class="first">An <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> containing, for each <tt class="docutils literal"><span class="pre">a</span></tt><em>i</em>,</p>
<ul class="last simple">
<li>if <tt class="docutils literal"><span class="pre">a</span></tt><em>i</em>, is a single-element <span class="concept">ArgumentPack</span>, its element</li>
<li>Otherwise, a <a class="reference" href="#tagged-reference">tagged reference</a> with <a class="reference" href="#kw">keyword</a> <tt class="docutils literal"><span class="pre">K</span></tt><em>i</em> and <em>value</em> <tt class="docutils literal"><span class="pre">a</span></tt><em>i</em></li>
</ul>
</td>
</tr>
</tbody>
</table>
</dd>
</dl>
</div>
<div class="section">
<h2><a class="toc-backref" href="#id42" id="optional-required" name="optional-required"><span id="required"></span><span id="optional"></span>4.3 <tt class="docutils literal"><span class="pre">optional</span></tt>, <tt class="docutils literal"><span class="pre">required</span></tt></a></h2>
<p>These templates describe the requirements on a function parameter.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/parameters.hpp">boost/parameter/parameters.hpp</a></td>
</tr>
</tbody>
</table>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name" colspan="2">Specializations model:</th></tr>
<tr><td> </td><td class="field-body"><a class="reference" href="#parameterspec"><span class="concept">ParameterSpec</span></a></td>
</tr>
</tbody>
</table>
<pre class="literal-block">
template <class Tag, class Predicate = <em>unspecified</em>>
struct optional;
template <class Tag, class Predicate = <em>unspecified</em>>
struct required;
</pre>
<p>The default value of <tt class="docutils literal"><span class="pre">Predicate</span></tt> is an unspecified <a class="reference" href="../../../mpl/doc/refmanual/metafunction.html"><span class="concept">Metafunction</span></a> that returns
<tt class="docutils literal"><span class="pre">mpl::true_</span></tt> for any argument.</p>
</div>
<div class="section">
<h2><a class="toc-backref" href="#id43" id="deduced" name="deduced">4.4 <tt class="docutils literal"><span class="pre">deduced</span></tt></a></h2>
<p>This template is used to wrap the <em>keyword tag</em> argument to
<tt class="docutils literal"><span class="pre">optional</span></tt> or <tt class="docutils literal"><span class="pre">required</span></tt>.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/parameters.hpp">boost/parameter/parameters.hpp</a></td>
</tr>
</tbody>
</table>
<pre class="literal-block">
template <class Tag>
struct deduced;
</pre>
</div>
</div>
<hr class="docutils" />
<div class="section">
<h1><a class="toc-backref" href="#id44" id="metafunctions" name="metafunctions">5 Metafunctions</a></h1>
<p>A <a class="reference" href="../../../mpl/doc/refmanual/metafunction.html"><span class="concept">Metafunction</span></a> is conceptually a function that operates on, and
returns, C++ types.</p>
<div class="section">
<h2><a class="toc-backref" href="#id45" id="binding" name="binding">5.1 <tt class="docutils literal"><span class="pre">binding</span></tt></a></h2>
<p>Returns the result type of indexing an argument pack with a
<a class="reference" href="#keyword-tag-type">keyword tag type</a> or with a <a class="reference" href="#tagged-default">tagged default</a>.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Defined n:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/binding.hpp">boost/parameter/binding.hpp</a></td>
</tr>
</tbody>
</table>
<pre class="literal-block">
template <class A, class K, class D = void>
struct binding
{
typedef … type;
};
</pre>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><tt class="docutils literal"><span class="pre">A</span></tt> is a model of <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a>.</td>
</tr>
<tr class="field"><th class="field-name">Returns:</th><td class="field-body">the reference type of the <a class="reference" href="#tagged-reference">tagged reference</a> in <tt class="docutils literal"><span class="pre">A</span></tt>
having <a class="reference" href="#keyword-tag-type">keyword tag type</a> <tt class="docutils literal"><span class="pre">K</span></tt>, if any. If no such <a class="reference" href="#tagged-reference">tagged reference</a> exists, returns <tt class="docutils literal"><span class="pre">D</span></tt>.</td>
</tr>
</tbody>
</table>
</div>
<div class="section">
<h2><a class="toc-backref" href="#id46" id="lazy-binding" name="lazy-binding">5.2 <tt class="docutils literal"><span class="pre">lazy_binding</span></tt></a></h2>
<p>Returns the result type of indexing an argument pack with a <a class="reference" href="#tagged-lazy-default">tagged lazy default</a>.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/binding.hpp">boost/parameter/binding.hpp</a></td>
</tr>
</tbody>
</table>
<pre class="literal-block">
template <class A, class K, class F>
struct lazy_binding
{
typedef … type;
};
</pre>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><tt class="docutils literal"><span class="pre">A</span></tt> is a model of <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a>.</td>
</tr>
<tr class="field"><th class="field-name">Returns:</th><td class="field-body">the reference type of the <a class="reference" href="#tagged-reference">tagged reference</a> in <tt class="docutils literal"><span class="pre">A</span></tt>
having <a class="reference" href="#keyword-tag-type">keyword tag type</a> <tt class="docutils literal"><span class="pre">K</span></tt>, if any. If no such <a class="reference" href="#tagged-reference">tagged reference</a> exists, returns <tt class="docutils literal"><span class="pre">boost::</span></tt><a class="reference" href="../../../utility/utility.htm#result_of"><tt class="docutils literal"><span class="pre">result_of</span></tt></a><tt class="docutils literal"><span class="pre"><F()>::type</span></tt>.<a class="footnote-reference" href="#no-result-of" id="id18" name="id18"><sup>2</sup></a></td>
</tr>
</tbody>
</table>
</div>
<div class="section">
<h2><a class="toc-backref" href="#id47" id="value-type" name="value-type">5.3 <tt class="docutils literal"><span class="pre">value_type</span></tt></a></h2>
<p>Returns the result type of indexing an argument pack with a
<a class="reference" href="#keyword-tag-type">keyword tag type</a> or with a <a class="reference" href="#tagged-default">tagged default</a>.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Defined n:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/value_type.hpp">boost/parameter/value_type.hpp</a></td>
</tr>
</tbody>
</table>
<pre class="literal-block">
template <class A, class K, class D = void>
struct value_type
{
typedef … type;
};
</pre>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><p class="first"><tt class="docutils literal"><span class="pre">A</span></tt> is a model of <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a>.</p>
</td>
</tr>
<tr class="field"><th class="field-name">Returns:</th><td class="field-body"><p class="first">the type of the <a class="reference" href="#tagged-reference">tagged reference</a> in <tt class="docutils literal"><span class="pre">A</span></tt>
having <a class="reference" href="#keyword-tag-type">keyword tag type</a> <tt class="docutils literal"><span class="pre">K</span></tt>, if any. If no such <a class="reference" href="#tagged-reference">tagged reference</a> exists, returns <tt class="docutils literal"><span class="pre">D</span></tt>. Equivalent to:</p>
<pre class="literal-block">
typename remove_reference<
typename binding<A, K, D>::type
>::type
</pre>
<p class="last">… when <tt class="docutils literal"><span class="pre">D</span></tt> is not a reference type.</p>
</td>
</tr>
</tbody>
</table>
</div>
</div>
<hr class="docutils" />
<div class="section">
<h1><a class="toc-backref" href="#id48" id="code-generation-macros" name="code-generation-macros">6 Code Generation Macros</a></h1>
<p>Macros in this section can be used to ease the writing of code
using the Parameter libray by eliminating repetitive boilerplate.</p>
<div class="section">
<h2><a class="toc-backref" href="#id49" id="boost-parameter-function-result-name-tag-namespace-arguments" name="boost-parameter-function-result-name-tag-namespace-arguments">6.1 <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_FUNCTION(result,name,tag_namespace,arguments)</span></tt></a></h2>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/preprocessor.hpp">boost/parameter/preprocessor.hpp</a></td>
</tr>
</tbody>
</table>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><p class="first"><tt class="docutils literal"><span class="pre">result</span></tt> is the parenthesized return type of the function.
<tt class="docutils literal"><span class="pre">name</span></tt> is the base name of the function, this is the name of the
generated forwarding functions. <tt class="docutils literal"><span class="pre">tag_namespace</span></tt> is the namespace in
which the keywords used by the function resides. <tt class="docutils literal"><span class="pre">arguments</span></tt> is
a list of <em>argument specifiers</em>, as defined below.</p>
</td>
</tr>
<tr class="field"><th class="field-name" colspan="2">Argument specifiers syntax:</th></tr>
<tr><td> </td><td class="field-body"><pre class="first literal-block">
argument-specifiers ::= <em>specifier-group</em> {<em>specifier-group</em>}
specifier-group0 ::= <em>specifier-group1</em> |
( '<strong>(</strong>' '<strong>deduced</strong>' <em>specifier-group1</em> {<em>specifier-group1</em>} '<strong>)</strong>' )
specifier-group1 ::= ( '<strong>(</strong>' '<strong>optional</strong>' <em>optional-specifier</em> {<em>optional-specifier</em>} '<strong>)</strong>' ) |
( '<strong>(</strong>' '<strong>required</strong>' <em>required-specifier</em> {<em>required-specifier</em>} '<strong>)</strong>' )
optional-specifier ::= '<strong>(</strong>' <em>name</em> '<strong>,</strong>' <em>restriction</em> '<strong>,</strong>' <em>default-value</em> ')'
required-specifier ::= '<strong>(</strong>' <em>name</em> '<strong>,</strong>' <em>restriction</em> ')'
restriction ::= ('<strong>*</strong>' '<strong>(</strong>' <em>lambda-expression</em> '<strong>)</strong>' ) |
( '<strong>(</strong>' <em>typename</em> '<strong>)</strong>' ) |
'<strong>*</strong>'
</pre>
<p class="last"><tt class="docutils literal"><span class="pre">name</span></tt> is any valid C++ identifier. <tt class="docutils literal"><span class="pre">default-value</span></tt> is any valid
C++ expression. <tt class="docutils literal"><span class="pre">typename</span></tt> is the name of a type.
<tt class="docutils literal"><span class="pre">lambda-expression</span></tt> is an <a class="reference" href="../../../mpl/doc/refmanual/lambda-expression.html">MPL lambda expression</a>.</p>
</td>
</tr>
</tbody>
</table>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name" colspan="2">Generated names in enclosing scope:</th></tr>
<tr><td> </td><td class="field-body"><ul class="first last simple">
<li><tt class="docutils literal"><span class="pre">boost_param_result_</span> <span class="pre">##</span> <span class="pre">__LINE__</span> <span class="pre">##</span> <span class="pre">name</span></tt></li>
<li><tt class="docutils literal"><span class="pre">boost_param_params_</span> <span class="pre">##</span> <span class="pre">__LINE__</span> <span class="pre">##</span> <span class="pre">name</span></tt></li>
<li><tt class="docutils literal"><span class="pre">boost_param_parameters_</span> <span class="pre">##</span> <span class="pre">__LINE__</span> <span class="pre">##</span> <span class="pre">name</span></tt></li>
<li><tt class="docutils literal"><span class="pre">boost_param_impl</span> <span class="pre">##</span> <span class="pre">name</span></tt></li>
<li><tt class="docutils literal"><span class="pre">boost_param_default_</span> <span class="pre">##</span> <span class="pre">__LINE__</span> <span class="pre">##</span> <span class="pre">name</span></tt></li>
</ul>
</td>
</tr>
</tbody>
</table>
<dl class="docutils">
<dt>Approximate expansion:</dt>
<dd><p class="first"><strong>Where</strong>:</p>
<ul class="simple">
<li><tt class="docutils literal"><span class="pre">n</span></tt> denotes the <em>minimum</em> arity, as determined from <tt class="docutils literal"><span class="pre">arguments</span></tt>.</li>
<li><tt class="docutils literal"><span class="pre">m</span></tt> denotes the <em>maximum</em> arity, as determined from <tt class="docutils literal"><span class="pre">arguments</span></tt>.</li>
</ul>
<pre class="last literal-block">
template <class T>
struct boost_param_result_ ## __LINE__ ## <strong>name</strong>
{
typedef <strong>result</strong> type;
};
struct boost_param_params_ ## __LINE__ ## <strong>name</strong>
: boost::parameter::parameters<
<em>list of parameter specifications, based on arguments</em>
>
{};
typedef boost_param_params_ ## __LINE__ ## <strong>name</strong>
boost_param_parameters_ ## __LINE__ ## <strong>name</strong>;
template <class A0, …, class A<strong>n</strong>>
<em>result type</em> <strong>name</strong>(
A0 <em>cv</em>& a0, …, A<strong>n</strong> <em>cv</em>& a<strong>n</strong>
, typename boost_param_parameters_ ## __LINE__ ## <strong>name</strong>::match<
A0 <em>cv</em>, …, A<strong>n</strong> <em>cv</em>
>::type = boost_param_parameters_ ## __LINE__ ## <strong>name</strong>()
)
{
<em>… forward to implementation …</em>
}
<span class="vellipsis">⋮</span>
template <class A0, …, class A<strong>m</strong>>
<em>result type</em> <strong>name</strong>(
A0 <em>cv</em>& a0, …, A<strong>m</strong> <em>cv</em>& a<strong>m</strong>
, typename boost_param_parameters_ ## __LINE__ ## <strong>name</strong>::match<
A0 <em>cv</em>, …, A<strong>m</strong> <em>cv</em>
>::type = boost_param_parameters_ ## __LINE__ ## <strong>name</strong>()
)
{
<em>… forward to implementation …</em>
}
template <
class ResultType
, class <em>argument name</em><strong>0</strong> ## _type
…
, class <em>argument name</em><strong>m</strong> ## _type
>
ResultType boost_param_default_ ## __LINE__ ## <strong>name</strong>(
(ResultType(*)())
, <em>argument name</em><strong>0</strong> ## _type& <em>argument name</em><strong>0</strong>
…
, <em>argument name</em><strong>m</strong> ## _type& <em>argument name</em><strong>m</strong>
)
</pre>
</dd>
</dl>
</div>
<div class="section">
<h2><a class="toc-backref" href="#id50" id="boost-parameter-member-function-result-name-tag-namespace-arguments" name="boost-parameter-member-function-result-name-tag-namespace-arguments">6.2 <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_MEMBER_FUNCTION(result,name,tag_namespace,arguments)</span></tt></a></h2>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/preprocessor.hpp">boost/parameter/preprocessor.hpp</a></td>
</tr>
</tbody>
</table>
<p>See <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_FUNCTION(result,name,tag_namespace,arguments)</span></tt></p>
</div>
<div class="section">
<h2><a class="toc-backref" href="#id51" id="boost-parameter-constructor-cls-impl-tag-namespace-arguments" name="boost-parameter-constructor-cls-impl-tag-namespace-arguments">6.3 <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_CONSTRUCTOR(cls,</span> <span class="pre">impl,</span> <span class="pre">tag_namespace,</span> <span class="pre">arguments)</span></tt></a></h2>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/preprocessor.hpp">boost/parameter/preprocessor.hpp</a></td>
</tr>
</tbody>
</table>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><p class="first"><tt class="docutils literal"><span class="pre">cls</span></tt> is the name of this class. <tt class="docutils literal"><span class="pre">impl</span></tt> is the
parenthesized implementation base class for <tt class="docutils literal"><span class="pre">cls</span></tt>.
<tt class="docutils literal"><span class="pre">tag_namespace</span></tt> is the namespace in which the keywords
used by the function resides. <tt class="docutils literal"><span class="pre">arguments</span></tt> is
a list of <em>argument specifiers</em>, as defined in
<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_FUNCTION(result,name,tag_namespace,arguments)</span></tt>.</p>
</td>
</tr>
<tr class="field"><th class="field-name" colspan="2">Generated names in enclosing scope:</th></tr>
<tr><td> </td><td class="field-body"><ul class="first last simple">
<li><tt class="docutils literal"><span class="pre">boost_param_params_</span> <span class="pre">##</span> <span class="pre">__LINE__</span> <span class="pre">##</span> <span class="pre">ctor</span></tt></li>
<li><tt class="docutils literal"><span class="pre">constructor_parameters</span> <span class="pre">##</span> <span class="pre">__LINE__</span></tt></li>
</ul>
</td>
</tr>
</tbody>
</table>
<dl class="docutils">
<dt>Approximate expansion:</dt>
<dd><p class="first"><strong>Where</strong>:</p>
<ul class="simple">
<li><tt class="docutils literal"><span class="pre">n</span></tt> denotes the <em>minimum</em> arity, as determined from <tt class="docutils literal"><span class="pre">arguments</span></tt>.</li>
<li><tt class="docutils literal"><span class="pre">m</span></tt> denotes the <em>maximum</em> arity, as determined from <tt class="docutils literal"><span class="pre">arguments</span></tt>.</li>
</ul>
<pre class="last literal-block">
struct boost_param_params_ ## __LINE__ ## ctor
: boost::parameter::parameters<
<em>list of parameter specifications, based on arguments</em>
>
{};
typedef boost_param_params_ ## __LINE__ ## <strong>name</strong>
constructor_parameters ## __LINE__;
template <class A0, …, class A<strong>n</strong>>
<em>cls</em>(A0 const& a0, …, A<strong>n</strong> const& a<strong>n</strong>)
: <em>impl</em>(constructor_parameters ## __LINE__(a0, …, a<strong>n</strong>))
{}
<span class="vellipsis">⋮</span>
template <class A0, …, class A<strong>m</strong>>
<em>cls</em>(A0 const& a0, …, A<strong>n</strong> const& a<strong>m</strong>)
: <em>impl</em>(constructor_parameters ## __LINE__(a0, …, a<strong>m</strong>))
{}
</pre>
</dd>
</dl>
</div>
<div class="section">
<h2><a class="toc-backref" href="#id52" id="boost-parameter-name-name" name="boost-parameter-name-name">6.4 <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_NAME(name)</span></tt></a></h2>
<p>Declares a tag-type and keyword object.</p>
<p>Expands to:</p>
<p><strong>If</strong> <em>name</em> is of the form:</p>
<pre class="literal-block">
(<em>tag-name</em>, <em>namespace-name</em>) <em>object-name</em>
</pre>
<p><strong>then</strong></p>
<pre class="literal-block">
namespace <em>namespace-name</em>
{
struct <em>tag-name</em>
{
static char const* keyword_name()
{
return ##<em>tag-name</em>;
}
typedef <em>implementation defined</em> _;
typedef <em>implementation defined</em> _1;
};
}
::boost::parameter::keyword<<em>tag-namespace</em>::<em>tag-name</em>> const& <em>object-name</em>
= ::boost::parameter::keyword<<em>tag-namespace</em>::<em>tag-name</em>>::instance;
</pre>
<p><strong>Else</strong></p>
<pre class="literal-block">
namespace tag
{
struct <em>name</em>
{
static char const* keyword_name()
{
return ##<em>name</em>;
}
typedef <em>implementation defined</em> _;
typedef <em>implementation defined</em> _1;
};
}
::boost::parameter::keyword<tag::<em>name</em>> const& _<em>name</em>
= ::boost::parameter::keyword<tag::<em>name</em>>::instance;
</pre>
</div>
<div class="section">
<h2><a class="toc-backref" href="#id53" id="boost-parameter-template-keyword-name" name="boost-parameter-template-keyword-name">6.5 <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_TEMPLATE_KEYWORD(name)</span></tt></a></h2>
<p>Expands to:</p>
<pre class="literal-block">
namespace tag
{
struct <em>name</em>;
}
template <class T>
struct <em>name</em>
: ::boost::parameter::template_keyword<tag::<em>name</em>, T>
{};
</pre>
</div>
<div class="section">
<h2><a class="toc-backref" href="#id54" id="boost-parameter-fun-r-n-l-h-p" name="boost-parameter-fun-r-n-l-h-p">6.6 <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_FUN(r,n,l,h,p)</span></tt></a></h2>
<div class="admonition-deprecated admonition">
<p class="first admonition-title">Deprecated</p>
<p class="last">This macro has been deprecated in favor of
<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_FUNCTION</span></tt>.</p>
</div>
<p>Generates a sequence of <a class="reference" href="index.html#forwarding-functions">forwarding function</a> templates named
<tt class="docutils literal"><span class="pre">n</span></tt>, with arities ranging from <tt class="docutils literal"><span class="pre">l</span></tt> to <tt class="docutils literal"><span class="pre">h</span></tt> , returning <tt class="docutils literal"><span class="pre">r</span></tt>,
and using <tt class="docutils literal"><span class="pre">p</span></tt> to control overload resolution and assign tags to
positional arguments.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/macros.hpp">boost/parameter/macros.hpp</a></td>
</tr>
</tbody>
</table>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><tt class="docutils literal"><span class="pre">l</span></tt> and <tt class="docutils literal"><span class="pre">h</span></tt> are nonnegative integer tokens such
that <tt class="docutils literal"><span class="pre">l</span></tt> < <tt class="docutils literal"><span class="pre">h</span></tt></td>
</tr>
</tbody>
</table>
<dl class="docutils">
<dt>Generates</dt>
<dd><pre class="first last literal-block">
template <class A1, class A2, …class A##<strong>l</strong>>
r name(
A1 const& a1, A2 const& a2, …A<strong>l</strong> const& x<strong>l</strong>
, typename <strong>p</strong>::match<A1,A2,…A<strong>l</strong>>::type p = <strong>p</strong>())
{
return <strong>name</strong>_with_named_params(<strong>p</strong>(x1,x2,…x<strong>l</strong>));
}
template <class A1, class A2, …class A<strong>l</strong>, class A##<a class="reference" href="../../../preprocessor/doc/ref/inc.html">BOOST_PP_INC</a>(<strong>l</strong>)>
r name(
A1 const& a1, A2 const& a2, …A<strong>l</strong> const& x<strong>l</strong>
, A##<a class="reference" href="../../../preprocessor/doc/ref/inc.html">BOOST_PP_INC</a>(<strong>l</strong>) const& x##<a class="reference" href="../../../preprocessor/doc/ref/inc.html">BOOST_PP_INC</a>(<strong>l</strong>)
, typename <strong>p</strong>::match<A1,A2,…A<strong>l</strong>,A##<a class="reference" href="../../../preprocessor/doc/ref/inc.html">BOOST_PP_INC</a>(<strong>l</strong>)>::type p = <strong>p</strong>())
{
return <strong>name</strong>_with_named_params(<strong>p</strong>(x1,x2,…x<strong>l</strong>,x##<a class="reference" href="../../../preprocessor/doc/ref/inc.html">BOOST_PP_INC</a>(<strong>l</strong>)));
}
<span class="vellipsis">⋮</span>
template <class A1, class A2, …class A<strong>h</strong>>
r name(
A1 const& a1, A2 const& a2, …A<strong>h</strong> const& x<strong>h</strong>
, typename <strong>p</strong>::match<A1,A2,…A<strong>h</strong>>::type p = <strong>p</strong>())
{
return <strong>name</strong>_with_named_params(<strong>p</strong>(a1,a2,…a<strong>h</strong>));
}
</pre>
</dd>
</dl>
</div>
<div class="section">
<h2><a class="toc-backref" href="#id55" id="boost-parameter-keyword-n-k" name="boost-parameter-keyword-n-k">6.7 <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_KEYWORD(n,k)</span></tt></a></h2>
<div class="admonition-deprecated admonition">
<p class="first admonition-title">Deprecated</p>
<p class="last">This macro has been deprecated in favor of
<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_NAME</span></tt>.</p>
</div>
<p>Generates the declaration of a <a class="reference" href="#keyword-tag-type">keyword tag type</a> named <tt class="docutils literal"><span class="pre">k</span></tt> in
namespace <tt class="docutils literal"><span class="pre">n</span></tt>, and a corresponding <a class="reference" href="#keyword-object">keyword object</a> definition in
the enclosing namespace.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/keyword.hpp">boost/parameter/keyword.hpp</a></td>
</tr>
</tbody>
</table>
<dl class="docutils">
<dt>Generates</dt>
<dd><pre class="first last literal-block">
namespace <strong>n</strong> { struct <strong>k</strong>; }
namespace {
boost::parameter::keyword<<em>tag-namespace</em>::<strong>k</strong>>& <strong>k</strong>
= boost::parameter::keyword<<em>tag-namespace</em>::<strong>k</strong>>::get();
}
</pre>
</dd>
</dl>
</div>
<div class="section">
<h2><a class="toc-backref" href="#id56" id="boost-parameter-match-p-a-x" name="boost-parameter-match-p-a-x">6.8 <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_MATCH(p,a,x)</span></tt></a></h2>
<p>Generates a defaulted parameter declaration for a <a class="reference" href="index.html#forwarding-functions">forwarding
function</a>.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/match.hpp">boost/parameter/match.hpp</a></td>
</tr>
</tbody>
</table>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><p class="first"><tt class="docutils literal"><span class="pre">a</span></tt> is a <a class="reference" href="http://www.boost.org/libs/preprocessor/doc/data.html">Boost.Preprocessor sequence</a>
of the form</p>
<pre class="last literal-block">
(A0)(A1)…(A<em>n</em>)
</pre>
</td>
</tr>
</tbody>
</table>
<dl class="docutils">
<dt>Generates</dt>
<dd><pre class="first last literal-block">
typename <strong>p</strong>::match<<strong>A0</strong>,<strong>A1</strong>…,<strong>A</strong><em>n</em>>::type <strong>x</strong> = <strong>p</strong>()
</pre>
</dd>
</dl>
</div>
</div>
<div class="section">
<h1><a class="toc-backref" href="#id57" id="configuration-macros" name="configuration-macros">7 Configuration Macros</a></h1>
<div class="section">
<h2><a class="toc-backref" href="#id58" id="boost-parameter-max-arity" name="boost-parameter-max-arity">7.1 <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_MAX_ARITY</span></tt></a></h2>
<p>Determines the maximum number of arguments supported by the
library. Will only be <tt class="docutils literal"><span class="pre">#defined</span></tt> by the library if it is not
already <tt class="docutils literal"><span class="pre">#defined</span></tt>.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/config.hpp">boost/parameter/config.hpp</a></td>
</tr>
</tbody>
</table>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Default Value:</th><td class="field-body"><tt class="docutils literal"><span class="pre">5</span></tt></td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="section">
<h1><a class="toc-backref" href="#id59" id="tutorial" name="tutorial">8 Tutorial</a></h1>
<p>Follow <a class="reference" href="index.html#tutorial">this link</a> to the Boost.Parameter tutorial
documentation.</p>
<hr class="docutils" />
<table class="docutils footnote" frame="void" id="thread" rules="none">
<colgroup><col class="label" /><col /></colgroup>
<tbody valign="top">
<tr><td class="label"><a class="fn-backref" href="#id2" name="thread">[1]</a></td><td>References to tag objects may be initialized multiple
times. This scenario can only occur in the presence of
threading. Because the C++ standard doesn't consider threading,
it doesn't explicitly allow or forbid multiple initialization of
references. That said, it's hard to imagine an implementation
where it could make a difference.</td></tr>
</tbody>
</table>
<table class="docutils footnote" frame="void" id="no-result-of" rules="none">
<colgroup><col class="label" /><col /></colgroup>
<tbody valign="top">
<tr><td class="label"><a name="no-result-of">[2]</a></td><td><em>(<a class="fn-backref" href="#id11">1</a>, <a class="fn-backref" href="#id18">2</a>)</em> Where <a class="reference" href="../../../utility/utility.htm#BOOST_NO_RESULT_OF"><tt class="docutils literal"><span class="pre">BOOST_NO_RESULT_OF</span></tt></a> is <tt class="docutils literal"><span class="pre">#defined</span></tt>,
<tt class="docutils literal"><span class="pre">boost::</span></tt><a class="reference" href="../../../utility/utility.htm#result_of"><tt class="docutils literal"><span class="pre">result_of</span></tt></a><tt class="docutils literal"><span class="pre"><F()>::type</span></tt> is replaced by
<tt class="docutils literal"><span class="pre">F::result_type</span></tt>.</td></tr>
</tbody>
</table>
</div>
</div>
<div class="footer">
<hr class="footer" />
Generated on: 2007-05-03 14:17 UTC.
Generated by <a class="reference" href="http://docutils.sourceforge.net/">Docutils</a> from <a class="reference" href="http://docutils.sourceforge.net/rst.html">reStructuredText</a> source.
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