boost-react-native-bundle

<?xml version="1.0" encoding="utf-8" ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <meta name="generator" content="Docutils 0.6: http://docutils.sourceforge.net/" /> <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)" /> <link rel="stylesheet" href="rst.css" type="text/css" /> </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 external" href="mailto:dave@boost-consulting.com">dave@boost-consulting.com</a>, <a class="last reference external" 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 external" 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 external" 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 external" href="../../../../index.htm"><img alt="Boost" src="../../../../boost.png" /></a></p> <hr class="docutils" /> <div class="contents topic" id="contents"> <p class="topic-title first">Contents</p> <ul class="auto-toc simple"> <li><a class="reference internal" href="#preliminaries" id="id30">1   Preliminaries</a><ul class="auto-toc"> <li><a class="reference internal" href="#namespaces" id="id31">1.1   Namespaces</a></li> <li><a class="reference internal" href="#exceptions" id="id32">1.2   Exceptions</a></li> <li><a class="reference internal" href="#thread-safety" id="id33">1.3   Thread Safety</a></li> <li><a class="reference internal" href="#typography" id="id34">1.4   Typography</a></li> </ul> </li> <li><a class="reference internal" href="#terminology" id="id35">2   Terminology</a></li> <li><a class="reference internal" href="#concepts" id="id36">3   Concepts</a><ul class="auto-toc"> <li><a class="reference internal" href="#argumentpack" id="id37">3.1   <span class="concept">ArgumentPack</span></a></li> <li><a class="reference internal" href="#id5" id="id38">3.2   <span class="concept">ParameterSpec</span></a></li> </ul> </li> <li><a class="reference internal" href="#class-templates" id="id39">4   Class Templates</a><ul class="auto-toc"> <li><a class="reference internal" href="#id7" id="id40">4.1   <tt class="docutils literal"><span class="pre">keyword</span></tt></a></li> <li><a class="reference internal" href="#parameters" id="id41">4.2   <tt class="docutils literal"><span class="pre">parameters</span></tt></a></li> <li><a class="reference internal" href="#optional-required" id="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 internal" href="#deduced" id="id43">4.4   <tt class="docutils literal"><span class="pre">deduced</span></tt></a></li> </ul> </li> <li><a class="reference internal" href="#metafunctions" id="id44">5   Metafunctions</a><ul class="auto-toc"> <li><a class="reference internal" href="#binding" id="id45">5.1   <tt class="docutils literal"><span class="pre">binding</span></tt></a></li> <li><a class="reference internal" href="#lazy-binding" id="id46">5.2   <tt class="docutils literal"><span class="pre">lazy_binding</span></tt></a></li> <li><a class="reference internal" href="#value-type" id="id47">5.3   <tt class="docutils literal"><span class="pre">value_type</span></tt></a></li> </ul> </li> <li><a class="reference internal" href="#code-generation-macros" id="id48">6   Code Generation Macros</a><ul class="auto-toc"> <li><a class="reference internal" href="#boost-parameter-function-result-name-tag-namespace-arguments" id="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 internal" href="#boost-parameter-member-function-result-name-tag-namespace-arguments" id="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 internal" href="#boost-parameter-constructor-cls-impl-tag-namespace-arguments" id="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 internal" href="#boost-parameter-name-name" id="id52">6.4   <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_NAME(name)</span></tt></a></li> <li><a class="reference internal" href="#boost-parameter-template-keyword-name" id="id53">6.5   <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_TEMPLATE_KEYWORD(name)</span></tt></a></li> <li><a class="reference internal" href="#boost-parameter-fun-r-n-l-h-p" id="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 internal" href="#boost-parameter-keyword-n-k" id="id55">6.7   <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_KEYWORD(n,k)</span></tt></a></li> <li><a class="reference internal" href="#boost-parameter-match-p-a-x" id="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 internal" href="#configuration-macros" id="id57">7   Configuration Macros</a><ul class="auto-toc"> <li><a class="reference internal" href="#boost-parameter-max-arity" id="id58">7.1   <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_MAX_ARITY</span></tt></a></li> </ul> </li> <li><a class="reference internal" href="#tutorial" id="id59">8   Tutorial</a></li> </ul> </div> <hr class="docutils" /> <div class="section" id="preliminaries"> <h1><a class="toc-backref" href="#id30">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" id="namespaces"> <h2><a class="toc-backref" href="#id31">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" id="exceptions"> <h2><a class="toc-backref" href="#id32">1.2   Exceptions</a></h2> <p>No operation described in this document throws an exception unless otherwise specified.</p> </div> <div class="section" id="thread-safety"> <h2><a class="toc-backref" href="#id33">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"><sup>1</sup></a></p> </div> <div class="section" id="typography"> <h2><a class="toc-backref" href="#id34">1.4   Typography</a></h2> <p>Names written in <span class="concept">sans serif type</span> represent <a class="reference external" href="http://www.boost.org/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 internal" 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" id="terminology"> <h1><a class="toc-backref" href="#id35">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 internal" 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 internal" 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 internal" 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 internal" 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 internal" 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 internal" 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 internal" 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 internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>” can refer to a type that models <a class="reference internal" 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" id="concepts"> <h1><a class="toc-backref" href="#id36">3   Concepts</a></h1> <p>This section describes the generic type <a class="reference external" href="http://www.boost.org/more/generic_programming.html#concept">concepts</a> used by the Parameter library.</p> <div class="section" id="argumentpack"> <h2><a class="toc-backref" href="#id37">3.1   <span class="concept">ArgumentPack</span></a></h2> <p>An <span class="concept">ArgumentPack</span> is a collection of <a class="reference internal" 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 external" href="../../../mpl/doc/refmanual/forward-sequence.html"><span class="concept">Forward Sequence</span></a> consisting of the <a class="reference internal" href="#keyword-tag-type">keyword tag type</a>s in its <a class="reference internal" href="#tagged-reference">tagged reference</a>s.</p> <div class="section" id="requirements"> <h3>Requirements</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 internal" 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 internal" href="#tagged-default">tagged default</a> with <a class="reference internal" 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 internal" href="#tagged-lazy-default">tagged lazy default</a> with <a class="reference internal" 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 internal" 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 internal" 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 internal" 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 internal" 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 internal" 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" id="id5"> <span id="parameterspec"></span><h2><a class="toc-backref" href="#id38">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 internal" 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 internal" 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 internal" 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 external" 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 internal" 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 internal" 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 external" href="index.html#controlling-overload-resolution">limit</a> the arguments that will be matched by <a class="reference external" href="index.html#forwarding-functions">forwarding functions</a>.</p> </div> </div> <hr class="docutils" /> <div class="section" id="class-templates"> <h1><a class="toc-backref" href="#id39">4   Class Templates</a></h1> <div class="section" id="id7"> <span id="keyword"></span><h2><a class="toc-backref" href="#id40">4.1   <tt class="docutils literal"><span class="pre">keyword</span></tt></a></h2> <p>The type of every <a class="reference internal" 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 external" 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 internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> <a class="reference internal" href="#operator">operator=</a>(T& value) const; template <class T> <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> <a class="reference internal" href="#operator">operator=</a>(T const& value) const; template <class T> <em>tagged default</em> <a class="reference internal" href="#id9">operator|</a>(T& x) const; template <class T> <em>tagged default</em> <a class="reference internal" href="#id9">operator|</a>(T const& x) const; template <class F> <em>tagged lazy default</em> <a class="reference internal" href="#id10">operator||</a>(F const&) const; static keyword<Tag>& <a class="reference internal" 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 internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> operator=(T& value) const; template <class T> <a class="reference internal" 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 internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> containing a single <a class="reference internal" href="#tagged-reference">tagged reference</a> to <tt class="docutils literal"><span class="pre">value</span></tt> with <a class="reference internal" 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 internal" href="#tagged-default">tagged default</a> with <em>value</em> <tt class="docutils literal"><span class="pre">x</span></tt> and <a class="reference internal" 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 external" 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"><sup>2</sup></a></td> </tr> <tr class="field"><th class="field-name">Returns:</th><td class="field-body">a <a class="reference internal" 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 internal" 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" id="parameters"> <h2><a class="toc-backref" href="#id41">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 internal" 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 external" 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 internal" href="#match">match</a> { typedef … type; }; template <class A0> <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> <a class="reference internal" href="#id13">operator()</a>(A0& a0) const; template <class A0, class A1> <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> <a class="reference internal" href="#id13">operator()</a>(A0& a0, A1& a1) const; <span class="vellipsis">⋮</span> template <class A0, class A1, …class Aβ> <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> <a class="reference internal" 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 internal" 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 internal" 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 internal" 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 internal" 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 internal" 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 internal" 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 external" href="../../../mpl/doc/refmanual/metafunction.html"><span class="concept">Metafunction</span></a> used to remove a <a class="reference external" 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 internal" 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 internal" 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 internal" 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 internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> <a class="reference internal" 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 internal" 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 internal" href="#tagged-reference">tagged reference</a> with <a class="reference internal" 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" id="optional-required"> <span id="required"></span><span id="optional"></span><h2><a class="toc-backref" href="#id42">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 external" 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 internal" 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 external" 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" id="deduced"> <h2><a class="toc-backref" href="#id43">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 external" 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" id="metafunctions"> <h1><a class="toc-backref" href="#id44">5   Metafunctions</a></h1> <p>A <a class="reference external" 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" id="binding"> <h2><a class="toc-backref" href="#id45">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 internal" href="#keyword-tag-type">keyword tag type</a> or with a <a class="reference internal" 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 external" 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 internal" 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 internal" href="#tagged-reference">tagged reference</a> in <tt class="docutils literal"><span class="pre">A</span></tt> having <a class="reference internal" 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 internal" 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" id="lazy-binding"> <h2><a class="toc-backref" href="#id46">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 internal" 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 external" 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 internal" 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 internal" href="#tagged-reference">tagged reference</a> in <tt class="docutils literal"><span class="pre">A</span></tt> having <a class="reference internal" 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 internal" href="#tagged-reference">tagged reference</a> exists, returns <tt class="docutils literal"><span class="pre">boost::</span></tt><a class="reference external" 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"><sup>2</sup></a></td> </tr> </tbody> </table> </div> <div class="section" id="value-type"> <h2><a class="toc-backref" href="#id47">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 internal" href="#keyword-tag-type">keyword tag type</a> or with a <a class="reference internal" 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 external" 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 internal" 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 internal" href="#tagged-reference">tagged reference</a> in <tt class="docutils literal"><span class="pre">A</span></tt> having <a class="reference internal" 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 internal" 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" id="code-generation-macros"> <h1><a class="toc-backref" href="#id48">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" id="boost-parameter-function-result-name-tag-namespace-arguments"> <h2><a class="toc-backref" href="#id49">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 external" 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-gr