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7315 lines
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<meta name="generator" content="Docutils 0.13: http://docutils.sourceforge.net/" />
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<title>The Boost Parameter Library Reference Documentation</title>
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<meta name="authors" content="David Abrahams Daniel Wallin" />
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<meta name="organization" content="BoostPro Computing" />
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<meta name="date" content="2005-07-17" />
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<meta name="copyright" content="Copyright David Abrahams, Daniel Wallin 2005-2009. 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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<body>
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<div class="document" id="the-boost-parameter-library-reference-documentation">
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<h1 class="title">The Boost Parameter Library Reference Documentation</h1>
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<table class="docinfo" frame="void" rules="none">
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<col class="docinfo-name" />
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<col class="docinfo-content" />
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<tbody valign="top">
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<tr><th class="docinfo-name">Authors:</th>
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<td>David Abrahams
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<br />Daniel Wallin</td></tr>
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<tr><th class="docinfo-name">Contact:</th>
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<td><a class="first reference external" href="mailto:dave@boost-consulting.com">dave@boost-consulting.com</a>, <a class="last reference external" href="mailto:daniel@boostpro.com">daniel@boostpro.com</a></td></tr>
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<tr><th class="docinfo-name">Organization:</th>
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<td><a class="first last reference external" href="http://www.boostpro.com">BoostPro Computing</a></td></tr>
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<tr><th class="docinfo-name">Date:</th>
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<td>2005-07-17</td></tr>
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<tr><th class="docinfo-name">Copyright:</th>
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<td>Copyright David Abrahams, Daniel Wallin
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2005-2009. Distributed under the Boost Software License,
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Version 1.0. (See accompanying file LICENSE_1_0.txt
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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>
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</tbody>
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</table>
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<p><a class="reference external" href="../../../../index.htm"><img alt="Boost" src="../../../../boost.png" /></a></p>
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<hr class="docutils" />
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<div class="contents topic" id="contents">
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<p class="topic-title first">Contents</p>
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<ul class="auto-toc simple">
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<li><a class="reference internal" href="#preliminaries" id="id31">1 Preliminaries</a><ul class="auto-toc">
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<li><a class="reference internal" href="#namespaces" id="id32">1.1 Namespaces</a></li>
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<li><a class="reference internal" href="#exceptions" id="id33">1.2 Exceptions</a></li>
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<li><a class="reference internal" href="#thread-safety" id="id34">1.3 Thread Safety</a></li>
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<li><a class="reference internal" href="#typography" id="id35">1.4 Typography</a></li>
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</ul>
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</li>
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<li><a class="reference internal" href="#terminology" id="id36">2 Terminology</a></li>
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<li><a class="reference internal" href="#concepts" id="id37">3 Concepts</a><ul class="auto-toc">
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<li><a class="reference internal" href="#argumentpack" id="id38">3.1 <span class="concept">ArgumentPack</span></a></li>
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<li><a class="reference internal" href="#id3" id="id39">3.2 <span class="concept">ParameterSpec</span></a></li>
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</ul>
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</li>
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<li><a class="reference internal" href="#class-templates" id="id40">4 Class Templates</a><ul class="auto-toc">
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<li><a class="reference internal" href="#id5" id="id41">4.1 <tt class="docutils literal">keyword</tt></a></li>
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<li><a class="reference internal" href="#id7" id="id42">4.2 <tt class="docutils literal">template_keyword</tt></a></li>
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<li><a class="reference internal" href="#id8" id="id43">4.3 <tt class="docutils literal">parameters</tt></a></li>
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<li><a class="reference internal" href="#optional-required" id="id44">4.4 <tt class="docutils literal">optional</tt>, <tt class="docutils literal">required</tt></a></li>
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<li><a class="reference internal" href="#id9" id="id45">4.5 <tt class="docutils literal">deduced</tt></a></li>
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</ul>
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</li>
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<li><a class="reference internal" href="#metafunctions" id="id46">5 Metafunctions</a><ul class="auto-toc">
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<li><a class="reference internal" href="#id10" id="id47">5.1 <tt class="docutils literal">binding</tt></a></li>
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<li><a class="reference internal" href="#id11" id="id48">5.2 <tt class="docutils literal">lazy_binding</tt></a></li>
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<li><a class="reference internal" href="#id13" id="id49">5.3 <tt class="docutils literal">value_type</tt></a></li>
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<li><a class="reference internal" href="#id14" id="id50">5.4 <tt class="docutils literal">lazy_value_type</tt></a></li>
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<li><a class="reference internal" href="#id16" id="id51">5.5 <tt class="docutils literal">are_tagged_arguments</tt></a></li>
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<li><a class="reference internal" href="#id17" id="id52">5.6 <tt class="docutils literal">is_argument_pack</tt></a></li>
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<li><a class="reference internal" href="#id18" id="id53">5.7 <tt class="docutils literal"><span class="pre">result_of::compose</span></tt></a></li>
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</ul>
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</li>
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<li><a class="reference internal" href="#function-templates" id="id54">6 Function Templates</a><ul class="auto-toc">
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<li><a class="reference internal" href="#id19" id="id55">6.1 <tt class="docutils literal">compose</tt></a></li>
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</ul>
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</li>
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<li><a class="reference internal" href="#code-generation-macros" id="id56">7 Code Generation Macros</a><ul class="auto-toc">
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<li><a class="reference internal" href="#boost-parameter-function-result-name-tag-namespace-arguments" id="id57">7.1 <tt class="docutils literal">BOOST_PARAMETER_FUNCTION(result, name, tag_namespace, arguments)</tt></a></li>
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<li><a class="reference internal" href="#boost-parameter-member-function-result-name-tag-namespace-arguments" id="id58">7.2 <tt class="docutils literal">BOOST_PARAMETER_MEMBER_FUNCTION(result, name, tag_namespace, arguments)</tt></a></li>
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<li><a class="reference internal" href="#boost-parameter-const-member-function-result-name-tag-ns-arguments" id="id59">7.3 <tt class="docutils literal">BOOST_PARAMETER_CONST_MEMBER_FUNCTION(result, name, tag_ns, arguments)</tt></a></li>
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<li><a class="reference internal" href="#boost-parameter-function-call-operator-result-tag-namespace-arguments" id="id60">7.4 <tt class="docutils literal">BOOST_PARAMETER_FUNCTION_CALL_OPERATOR(result, tag_namespace, arguments)</tt></a></li>
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<li><a class="reference internal" href="#boost-parameter-const-function-call-operator-result-tag-ns-arguments" id="id61">7.5 <tt class="docutils literal">BOOST_PARAMETER_CONST_FUNCTION_CALL_OPERATOR(result, tag_ns, arguments)</tt></a></li>
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<li><a class="reference internal" href="#boost-parameter-constructor-cls-impl-tag-namespace-arguments" id="id62">7.6 <tt class="docutils literal">BOOST_PARAMETER_CONSTRUCTOR(cls, impl, tag_namespace, arguments)</tt></a></li>
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<li><a class="reference internal" href="#boost-parameter-basic-function-result-name-tag-namespace-arguments" id="id63">7.7 <tt class="docutils literal">BOOST_PARAMETER_BASIC_FUNCTION(result, name, tag_namespace, arguments)</tt></a></li>
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<li><a class="reference internal" href="#boost-parameter-basic-member-function-result-name-tag-ns-arguments" id="id64">7.8 <tt class="docutils literal">BOOST_PARAMETER_BASIC_MEMBER_FUNCTION(result, name, tag_ns, arguments)</tt></a></li>
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<li><a class="reference internal" href="#boost-parameter-basic-const-member-function-result-name-tag-ns-args" id="id65">7.9 <tt class="docutils literal">BOOST_PARAMETER_BASIC_CONST_MEMBER_FUNCTION(result, name, tag_ns, args)</tt></a></li>
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<li><a class="reference internal" href="#boost-parameter-basic-function-call-operator-result-tag-ns-arguments" id="id66">7.10 <tt class="docutils literal">BOOST_PARAMETER_BASIC_FUNCTION_CALL_OPERATOR(result, tag_ns, arguments)</tt></a></li>
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<li><a class="reference internal" href="#boost-parameter-basic-const-function-call-operator-result-tag-ns-args" id="id67">7.11 <tt class="docutils literal">BOOST_PARAMETER_BASIC_CONST_FUNCTION_CALL_OPERATOR(result, tag_ns, args)</tt></a></li>
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<li><a class="reference internal" href="#boost-parameter-no-spec-function-result-name" id="id68">7.12 <tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_FUNCTION(result, name)</tt></a></li>
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<li><a class="reference internal" href="#boost-parameter-no-spec-member-function-result-name" id="id69">7.13 <tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_MEMBER_FUNCTION(result, name)</tt></a></li>
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<li><a class="reference internal" href="#boost-parameter-no-spec-const-member-function-result-name" id="id70">7.14 <tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_CONST_MEMBER_FUNCTION(result, name)</tt></a></li>
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<li><a class="reference internal" href="#boost-parameter-no-spec-function-call-operator-result" id="id71">7.15 <tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_FUNCTION_CALL_OPERATOR(result)</tt></a></li>
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<li><a class="reference internal" href="#boost-parameter-no-spec-const-function-call-operator-result" id="id72">7.16 <tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_CONST_FUNCTION_CALL_OPERATOR(result)</tt></a></li>
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<li><a class="reference internal" href="#boost-parameter-no-spec-constructor-cls-impl" id="id73">7.17 <tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_CONSTRUCTOR(cls, impl)</tt></a></li>
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<li><a class="reference internal" href="#boost-parameter-no-spec-no-base-constructor-cls-impl" id="id74">7.18 <tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_NO_BASE_CONSTRUCTOR(cls, impl)</tt></a></li>
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<li><a class="reference internal" href="#boost-parameter-name-name" id="id75">7.19 <tt class="docutils literal">BOOST_PARAMETER_NAME(name)</tt></a></li>
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<li><a class="reference internal" href="#boost-parameter-nested-keyword-tag-namespace-name-alias" id="id76">7.20 <tt class="docutils literal">BOOST_PARAMETER_NESTED_KEYWORD(tag_namespace, name, alias)</tt></a></li>
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<li><a class="reference internal" href="#boost-parameter-template-keyword-name" id="id77">7.21 <tt class="docutils literal">BOOST_PARAMETER_TEMPLATE_KEYWORD(name)</tt></a></li>
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<li><a class="reference internal" href="#boost-parameter-fun-r-n-l-h-p" id="id78">7.22 <tt class="docutils literal">BOOST_PARAMETER_FUN(r, n, l, h, p)</tt></a></li>
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<li><a class="reference internal" href="#boost-parameter-keyword-n-k" id="id79">7.23 <tt class="docutils literal">BOOST_PARAMETER_KEYWORD(n, k)</tt></a></li>
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<li><a class="reference internal" href="#boost-parameter-match-p-a-x" id="id80">7.24 <tt class="docutils literal">BOOST_PARAMETER_MATCH(p, a, x)</tt></a></li>
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</ul>
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</li>
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<li><a class="reference internal" href="#configuration-macros" id="id81">8 Configuration Macros</a><ul class="auto-toc">
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<li><a class="reference internal" href="#id21" id="id82">8.1 <tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a></li>
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<li><a class="reference internal" href="#id22" id="id83">8.2 <tt class="docutils literal">BOOST_PARAMETER_DISABLE_PERFECT_FORWARDING</tt></a></li>
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<li><a class="reference internal" href="#id23" id="id84">8.3 <tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt></a></li>
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<li><a class="reference internal" href="#id24" id="id85">8.4 <tt class="docutils literal">BOOST_PARAMETER_DISABLE_MP11_USAGE</tt></a></li>
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<li><a class="reference internal" href="#id25" id="id86">8.5 <tt class="docutils literal">BOOST_PARAMETER_VARIADIC_MPL_SEQUENCE</tt></a></li>
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<li><a class="reference internal" href="#id26" id="id87">8.6 <tt class="docutils literal">BOOST_PARAMETER_MAX_ARITY</tt></a></li>
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<li><a class="reference internal" href="#id27" id="id88">8.7 <tt class="docutils literal">BOOST_PARAMETER_COMPOSE_MAX_ARITY</tt></a></li>
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<li><a class="reference internal" href="#id28" id="id89">8.8 <tt class="docutils literal">BOOST_PARAMETER_EXPONENTIAL_OVERLOAD_THRESHOLD_ARITY</tt></a></li>
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<li><a class="reference internal" href="#outside-of-this-library" id="id90">8.9 ...Outside Of This Library</a></li>
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</ul>
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</li>
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<li><a class="reference internal" href="#tutorial" id="id91">9 Tutorial</a></li>
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</ul>
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</div>
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<hr class="docutils" />
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<div class="section" id="preliminaries">
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<h1><a class="toc-backref" href="#id31">1 Preliminaries</a></h1>
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<p>This section covers some basic information you'll need to know in order to
|
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understand this reference.</p>
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<div class="section" id="namespaces">
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<h2><a class="toc-backref" href="#id32">1.1 Namespaces</a></h2>
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<p>In this document, all unqualified identifiers should be assumed to be defined
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in namespace <tt class="docutils literal"><span class="pre">boost::parameter</span></tt> unless otherwise specified.</p>
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</div>
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<div class="section" id="exceptions">
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<h2><a class="toc-backref" href="#id33">1.2 Exceptions</a></h2>
|
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<p>No operation described in this document throws an exception unless otherwise
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specified.</p>
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</div>
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<div class="section" id="thread-safety">
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<h2><a class="toc-backref" href="#id34">1.3 Thread Safety</a></h2>
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<p>All components of this library can be used safely from multiple threads
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without synchronization.<a class="footnote-reference" href="#thread" id="id2"><sup>1</sup></a></p>
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</div>
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<div class="section" id="typography">
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<h2><a class="toc-backref" href="#id35">1.4 Typography</a></h2>
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<p>Names written in <span class="concept">sans serif type</span> represent <a class="reference internal" href="#concepts">concepts</a>.</p>
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<p>In code blocks, <em>italic type</em> represents unspecified text that satisfies the
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requirements given in the detailed description that follows the code block.</p>
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<p>In a specification of the tokens generated by a macro, <strong>bold type</strong> is used
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to highlight the position of the expanded macro argument in the result.</p>
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<p>The special character β represents the value of <a class="reference internal" href="#boost-parameter-max-arity"><tt class="docutils literal">BOOST_PARAMETER_MAX_ARITY</tt></a>.</p>
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</div>
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</div>
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<hr class="docutils" />
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<div class="section" id="terminology">
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<h1><a class="toc-backref" href="#id36">2 Terminology</a></h1>
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<dl class="docutils" id="kw">
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<dt>keyword</dt>
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<dd>The name of a function parameter.</dd>
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</dl>
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<span class="target" id="keyword-tag-type"></span><dl class="docutils">
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<dt>keyword tag type</dt>
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<dd>A type used to uniquely identify a function parameter. Typically its name
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will be the same as that of the parameter.</dd>
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</dl>
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<span class="target" id="positional"></span><dl class="docutils">
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<dt>positional argument</dt>
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<dd>An argument passed with no explicit keyword. Its parameter is determined
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in the usual C++ way: by position with respect to a parameter list.</dd>
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</dl>
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<span class="target" id="tag-type"></span><dl class="docutils">
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<dt>tag type</dt>
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<dd>Shorthand for “<a class="reference internal" href="#keyword-tag-type">keyword tag type</a>.”</dd>
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</dl>
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<span class="target" id="keyword-object"></span><dl class="docutils">
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<dt>keyword object</dt>
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<dd>An instance of <a class="reference internal" href="#keyword"><tt class="docutils literal">keyword</tt></a><tt class="docutils literal"><T></tt> for some <a class="reference internal" href="#tag-type">tag type</a> <tt class="docutils literal">T</tt>.</dd>
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</dl>
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<span class="target" id="tagged-reference"></span><dl class="docutils">
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<dt>tagged reference</dt>
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<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
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<em>keyword</em>), and that holds a reference (to the object's <em>value</em>).</p>
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<p class="last">As a shorthand, a “tagged reference to <tt class="docutils literal">x</tt>” means a tagged reference
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whose <em>value</em> is <tt class="docutils literal">x</tt>.</p>
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</dd>
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</dl>
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<span class="target" id="tagged-default"></span><dl class="docutils">
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<dt>tagged default</dt>
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<dd>A <a class="reference internal" href="#tagged-reference">tagged reference</a> whose <em>value</em> represents the value of a
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default argument.</dd>
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</dl>
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<span class="target" id="tagged-lazy-default"></span><dl class="docutils">
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<dt>tagged lazy default</dt>
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<dd>A <a class="reference internal" href="#tagged-reference">tagged reference</a> whose <em>value</em>, when invoked with no arguments,
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computes a default argument value.</dd>
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</dl>
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<span class="target" id="intended-argument-type"></span><dl class="docutils">
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<dt>intended argument type</dt>
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<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
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type of its element's <em>value</em>. The intended argument type of any other
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type <tt class="docutils literal">X</tt> is <tt class="docutils literal">X</tt> itself.</dd>
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</dl>
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<div class="note">
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<p class="first admonition-title">Note</p>
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<p class="last">In this reference, we will use concept names (and other names) to describe
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both types and objects, depending on context. So for example, “an
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<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>
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<em>or</em> an object of such a type.</p>
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</div>
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</div>
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<hr class="docutils" />
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<div class="section" id="concepts">
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<h1><a class="toc-backref" href="#id37">3 Concepts</a></h1>
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<p>This section describes the generic type concepts used by the Parameter
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library.</p>
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<div class="section" id="argumentpack">
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<h2><a class="toc-backref" href="#id38">3.1 <span class="concept">ArgumentPack</span></a></h2>
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<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
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arguments passed to a function. Every <span class="concept">ArgumentPack</span> is also a valid <a class="reference external" href="../../../mpl/doc/refmanual/forward-sequence.html">MPL
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Forward Sequence</a> and <a class="reference external" href="../../../mpl/doc/refmanual/associative-sequence.html">MPL Associative Sequence</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. If <tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt>
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is defined, then every <span class="concept">ArgumentPack</span> is also a valid <a class="reference external" href="../../../mp11/doc/html/mp11.html">Boost.MP11</a> map whose
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keys are <a class="reference internal" href="#keyword-tag-type">keyword tag type</a>s. The <a class="reference external" href="../../test/singular.cpp">singular.cpp</a>, <a class="reference external" href="../../test/compose.cpp">compose.cpp</a>, and
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<a class="reference external" href="../../test/mpl.cpp">mpl.cpp</a> test programs demonstrate this functionality.</p>
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<div class="section" id="requirements">
|
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<h3>Requirements</h3>
|
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<p>In the table below,</p>
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<ul class="simple">
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<li><tt class="docutils literal">A</tt> is a model of <span class="concept">ArgumentPack</span></li>
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<li><tt class="docutils literal">x</tt> is an instance of <tt class="docutils literal">A</tt></li>
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<li><tt class="docutils literal">u</tt> is a <a class="reference internal" href="#keyword-object">keyword object</a> of type <tt class="docutils literal">K</tt></li>
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<li><tt class="docutils literal">v</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">L</tt> and <em>value</em> of type <tt class="docutils literal">D</tt></li>
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<li><tt class="docutils literal">w</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">M</tt> and <em>value</em> of type <tt class="docutils literal">E const</tt></li>
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<li><tt class="docutils literal">z</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">keyword</tt></a><tt class="docutils literal"><span class="pre"><…>::operator=</span></tt>)</li>
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</ul>
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<p>Any exceptions thrown from the invocation of <tt class="docutils literal">w</tt>'s <em>value</em>
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will be propagated to the caller.</p>
|
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<table border="1" class="docutils">
|
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<caption><span class="concept">ArgumentPack</span> requirements</caption>
|
|
<colgroup>
|
|
<col width="14%" />
|
|
<col width="40%" />
|
|
<col width="19%" />
|
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<col width="27%" />
|
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</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">
|
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<tr><td><tt class="docutils literal">x[u]</tt></td>
|
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<td><tt class="docutils literal">binding<A, <span class="pre">K>::type</span></tt></td>
|
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<td><tt class="docutils literal">x</tt> contains
|
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an element <em>b</em>
|
|
whose <a class="reference internal" href="#kw">keyword</a> is
|
|
<tt class="docutils literal">K</tt></td>
|
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<td>Returns <em>b</em>'s
|
|
<em>value</em> (by
|
|
reference).</td>
|
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</tr>
|
|
<tr><td><tt class="docutils literal">x[u]</tt></td>
|
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<td><tt class="docutils literal">binding<A, L, <span class="pre">D>::type</span></tt></td>
|
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<td><em>none</em></td>
|
|
<td>If <tt class="docutils literal">x</tt> contains an
|
|
element <em>b</em> whose
|
|
<a class="reference internal" href="#kw">keyword</a> is the same as
|
|
<tt class="docutils literal">u</tt>'s, returns
|
|
<em>b</em>'s <em>value</em> (by
|
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reference).
|
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Otherwise, returns
|
|
<tt class="docutils literal">u</tt>'s <em>value</em>.</td>
|
|
</tr>
|
|
<tr><td><tt class="docutils literal">x[w]</tt></td>
|
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<td><tt class="docutils literal">lazy_binding<A, M, <span class="pre">E>::type</span></tt></td>
|
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<td><em>none</em></td>
|
|
<td>If <tt class="docutils literal">x</tt> contains an
|
|
element <em>b</em> whose
|
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<a class="reference internal" href="#kw">keyword</a> is the same as
|
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<tt class="docutils literal">w</tt>'s, returns
|
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<em>b</em>'s <em>value</em> (by
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reference).
|
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Otherwise, invokes
|
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<tt class="docutils literal">w</tt>'s <em>value</em>
|
|
and returns the
|
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result.</td>
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</tr>
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<tr><td><tt class="docutils literal">x, z</tt></td>
|
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<td>Model of <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a></td>
|
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<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">x</tt> and <tt class="docutils literal">z</tt>.</td>
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</tr>
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</tbody>
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</table>
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</div>
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</div>
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<div class="section" id="id3">
|
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<span id="parameterspec"></span><h2><a class="toc-backref" href="#id39">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">K</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">A</tt> is an <a class="reference internal" href="#intended-argument-type">intended argument type</a> associated with <tt class="docutils literal">K</tt>, if any</li>
|
|
<li><tt class="docutils literal">P</tt> is a model of <span class="concept">ArgumentPack</span> that contains <tt class="docutils literal">A</tt></li>
|
|
<li><tt class="docutils literal">F</tt> is an <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary Metafunction Class</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="14%" />
|
|
<col width="54%" />
|
|
</colgroup>
|
|
<thead valign="bottom">
|
|
<tr><th class="head">Type</th>
|
|
<th class="head"><tt class="docutils literal">A</tt>
|
|
required</th>
|
|
<th class="head">Condition <tt class="docutils literal">A</tt> must satisfy</th>
|
|
</tr>
|
|
</thead>
|
|
<tbody valign="top">
|
|
<tr><td><tt class="docutils literal">K</tt></td>
|
|
<td>no</td>
|
|
<td><em>n/a</em></td>
|
|
</tr>
|
|
<tr><td><a class="reference internal" href="#optional"><tt class="docutils literal">optional</tt></a><tt class="docutils literal"><K,F></tt></td>
|
|
<td>no</td>
|
|
<td><tt class="docutils literal"><span class="pre">mpl::apply2<F,A,P>::type::value</span></tt> is
|
|
<tt class="docutils literal">true</tt>.</td>
|
|
</tr>
|
|
<tr><td><a class="reference internal" href="#required"><tt class="docutils literal">required</tt></a><tt class="docutils literal"><K,F></tt></td>
|
|
<td>yes</td>
|
|
<td><tt class="docutils literal"><span class="pre">mpl::apply2<F,A,P>::type::value</span></tt> is
|
|
<tt class="docutils literal">true</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" />
|
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<div class="section" id="class-templates">
|
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<h1><a class="toc-backref" href="#id40">4 Class Templates</a></h1>
|
|
<div class="section" id="id5">
|
|
<span id="keyword"></span><h2><a class="toc-backref" href="#id41">4.1 <tt class="docutils literal">keyword</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">keyword</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 <typename Tag>
|
|
struct keyword
|
|
{
|
|
typedef Tag tag;
|
|
|
|
template <typename T>
|
|
constexpr typename <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a><
|
|
typename <a class="reference external" href="../../../mpl/doc/refmanual/eval-if.html">boost::mpl::eval_if</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_scalar.html">boost::is_scalar</a><T>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> // Enable this overload for scalar types.
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/eval-if.html">boost::mpl::eval_if</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_same.html">boost::is_same</a><
|
|
typename Tag::qualifier
|
|
, boost::parameter::in_reference
|
|
>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> // Enable this overload for "in" references.
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/if.html">mpl::if_</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_same.html">boost::is_same</a><
|
|
typename Tag::qualifier
|
|
, boost::parameter::forward_reference
|
|
>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> // Enable this overload for "forward" references.
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::false_</a> // Disable this overload for all other reference categories.
|
|
>
|
|
>
|
|
>::type
|
|
, <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>
|
|
>::type
|
|
<a class="reference internal" href="#assignment-operator"><tt class="docutils literal">operator=</tt></a>(T const& value) const;
|
|
|
|
template <typename T>
|
|
constexpr typename <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a><
|
|
typename <a class="reference external" href="../../../mpl/doc/refmanual/eval-if.html">boost::mpl::eval_if</a><
|
|
typename <a class="reference external" href="../../../mpl/doc/refmanual/eval-if.html">boost::mpl::eval_if</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_same.html">boost::is_same</a><
|
|
typename Tag::qualifier
|
|
, boost::parameter::out_reference
|
|
>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> // The reference category is "out".
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/if.html">mpl::if_</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_same.html">boost::is_same</a><
|
|
typename Tag::qualifier
|
|
, boost::parameter::forward_reference
|
|
>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> // The reference category is "forward".
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::false_</a> // The reference category is neither "out" nor "forward".
|
|
>
|
|
>::type
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/if.html">mpl::if_</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_const.html">boost::is_const</a><T>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::false_</a> // Disable this overload for reference-to-const types.
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> // Enable this overload for referece-to-mutable types.
|
|
>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::false_</a> // Disable this overload for references neither "out" nor "forward".
|
|
>::type
|
|
, <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>
|
|
>::type
|
|
<a class="reference internal" href="#assignment-operator"><tt class="docutils literal">operator=</tt></a>(T& value) const;
|
|
|
|
template <typename T>
|
|
constexpr typename <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a><
|
|
typename <a class="reference external" href="../../../mpl/doc/refmanual/eval-if.html">boost::mpl::eval_if</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_scalar.html">boost::is_scalar</a><T>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::false_</a> // Disable this overload for scalar types.
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/eval-if.html">boost::mpl::eval_if</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_same.html">boost::is_same</a><
|
|
typename Tag::qualifier
|
|
, boost::parameter::in_reference
|
|
>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> // Enable this overload for "in" references.
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/if.html">mpl::if_</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_same.html">boost::is_same</a><
|
|
typename Tag::qualifier
|
|
, boost::parameter::forward_reference
|
|
>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> // Enable this overload for "forward" references.
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::false_</a> // Disable this overload for all other reference categories.
|
|
>
|
|
>
|
|
>::type
|
|
, <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>
|
|
>::type
|
|
<a class="reference internal" href="#assignment-operator"><tt class="docutils literal">operator=</tt></a>(T const&& value) const;
|
|
|
|
template <typename T>
|
|
constexpr typename <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a><
|
|
typename <a class="reference external" href="../../../mpl/doc/refmanual/eval-if.html">boost::mpl::eval_if</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_scalar.html">boost::is_scalar</a><T>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::false_</a> // Disable this overload for scalar types.
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/eval-if.html">boost::mpl::eval_if</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_same.html">boost::is_same</a><
|
|
typename Tag::qualifier
|
|
, boost::parameter::consume_reference
|
|
>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> // Enable this overload for "consume" references.
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/if.html">mpl::if_</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_same.html">boost::is_same</a><
|
|
typename Tag::qualifier
|
|
, boost::parameter::forward_reference
|
|
>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> // Enable this overload for "forward" references.
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::false_</a> // Disable this overload for all other reference categories.
|
|
>
|
|
>
|
|
>::type
|
|
, <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>
|
|
>::type
|
|
<a class="reference internal" href="#assignment-operator"><tt class="docutils literal">operator=</tt></a>(T&& value) const;
|
|
|
|
template <typename T>
|
|
constexpr typename <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a><
|
|
typename <a class="reference external" href="../../../mpl/doc/refmanual/eval-if.html">boost::mpl::eval_if</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_scalar.html">boost::is_scalar</a><T>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> // Enable this overload for scalar types.
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/eval-if.html">boost::mpl::eval_if</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_same.html">boost::is_same</a><
|
|
typename Tag::qualifier
|
|
, boost::parameter::in_reference
|
|
>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> // Enable this overload for "in" references.
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/if.html">mpl::if_</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_same.html">boost::is_same</a><
|
|
typename Tag::qualifier
|
|
, boost::parameter::forward_reference
|
|
>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> // Enable this overload for "forward" references.
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::false_</a> // Disable this overload for all other reference categories.
|
|
>
|
|
>
|
|
>::type
|
|
, <em>tagged default</em>
|
|
>::type
|
|
<a class="reference internal" href="#bitwise-or-operator"><tt class="docutils literal">operator|</tt></a>(T const& x) const;
|
|
|
|
template <typename T>
|
|
constexpr typename <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a><
|
|
typename <a class="reference external" href="../../../mpl/doc/refmanual/eval-if.html">boost::mpl::eval_if</a><
|
|
typename <a class="reference external" href="../../../mpl/doc/refmanual/eval-if.html">boost::mpl::eval_if</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_same.html">boost::is_same</a><
|
|
typename Tag::qualifier
|
|
, boost::parameter::out_reference
|
|
>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> // The reference category is "out".
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/if.html">mpl::if_</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_same.html">boost::is_same</a><
|
|
typename Tag::qualifier
|
|
, boost::parameter::forward_reference
|
|
>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> // The reference category is "forward".
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::false_</a> // The reference category is neither "out" nor "forward".
|
|
>
|
|
>::type
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/if.html">mpl::if_</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_const.html">boost::is_const</a><T>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::false_</a> // Disable this overload for reference-to-const types.
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> // Enable this overload for referece-to-mutable types.
|
|
>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::false_</a> // Disable this overload for references neither "out" nor "forward".
|
|
>::type
|
|
, <em>tagged default</em>
|
|
>::type
|
|
<a class="reference internal" href="#bitwise-or-operator"><tt class="docutils literal">operator|</tt></a>(T& x) const;
|
|
|
|
template <typename T>
|
|
constexpr typename <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a><
|
|
typename <a class="reference external" href="../../../mpl/doc/refmanual/eval-if.html">boost::mpl::eval_if</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_scalar.html">boost::is_scalar</a><T>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::false_</a> // Disable this overload for scalar types.
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/eval-if.html">boost::mpl::eval_if</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_same.html">boost::is_same</a><
|
|
typename Tag::qualifier
|
|
, boost::parameter::in_reference
|
|
>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> // Enable this overload for "in" references.
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/if.html">mpl::if_</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_same.html">boost::is_same</a><
|
|
typename Tag::qualifier
|
|
, boost::parameter::forward_reference
|
|
>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> // Enable this overload for "forward" references.
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::false_</a> // Disable this overload for all other reference categories.
|
|
>
|
|
>
|
|
>::type
|
|
, <em>tagged default</em>
|
|
>::type
|
|
<a class="reference internal" href="#bitwise-or-operator"><tt class="docutils literal">operator|</tt></a>(T const&& x) const;
|
|
|
|
template <typename T>
|
|
constexpr typename <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a><
|
|
typename <a class="reference external" href="../../../mpl/doc/refmanual/eval-if.html">boost::mpl::eval_if</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_scalar.html">boost::is_scalar</a><T>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::false_</a> // Disable this overload for scalar types.
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/eval-if.html">boost::mpl::eval_if</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_same.html">boost::is_same</a><
|
|
typename Tag::qualifier
|
|
, boost::parameter::consume_reference
|
|
>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> // Enable this overload for "consume" references.
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/if.html">mpl::if_</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_same.html">boost::is_same</a><
|
|
typename Tag::qualifier
|
|
, boost::parameter::forward_reference
|
|
>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> // Enable this overload for "forward" references.
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::false_</a> // Disable this overload for all other reference categories.
|
|
>
|
|
>
|
|
>::type
|
|
, <em>tagged default</em>
|
|
>::type constexpr
|
|
<a class="reference internal" href="#bitwise-or-operator"><tt class="docutils literal">operator|</tt></a>(T&& value) const;
|
|
|
|
template <typename F>
|
|
constexpr <em>tagged lazy default</em> <a class="reference internal" href="#logical-or-operator"><tt class="docutils literal">operator||</tt></a>(F const&) const;
|
|
|
|
template <typename F>
|
|
constexpr <em>tagged lazy default</em> <a class="reference internal" href="#logical-or-operator"><tt class="docutils literal">operator||</tt></a>(F&) const;
|
|
|
|
static keyword<Tag> const& instance;
|
|
|
|
static keyword<Tag>& <a class="reference internal" href="#get">get</a>();
|
|
};
|
|
</pre>
|
|
<p id="assignment-operator"><tt class="docutils literal">operator=</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">Synopsis:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<pre class="literal-block">
|
|
template <typename T>
|
|
constexpr <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> operator=(T const& value) const;
|
|
|
|
template <typename T>
|
|
constexpr <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> operator=(T& value) const;
|
|
|
|
template <typename T>
|
|
constexpr <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> operator=(T const&& value) const;
|
|
|
|
template <typename T>
|
|
constexpr <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> operator=(T&& value) 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">one of the following:</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<ul class="simple">
|
|
<li>The nested <tt class="docutils literal">qualifier</tt> type of <tt class="docutils literal">Tag</tt> must be <tt class="docutils literal">forward_reference</tt>.</li>
|
|
<li>To use the <tt class="docutils literal">const</tt> lvalue reference overload, <tt class="docutils literal">T</tt> must be scalar, or
|
|
the nested <tt class="docutils literal">qualifier</tt> type of <tt class="docutils literal">Tag</tt> must be <tt class="docutils literal">in_reference</tt>.</li>
|
|
<li>To use the mutable lvalue reference overload, the nested <tt class="docutils literal">qualifier</tt>
|
|
type of <tt class="docutils literal">Tag</tt> must be <tt class="docutils literal">out_reference</tt> or <tt class="docutils literal">in_out_reference</tt>, and
|
|
<tt class="docutils literal">T</tt> must not be <tt class="docutils literal">const</tt>-qualified.</li>
|
|
<li>To use the <tt class="docutils literal">const</tt> rvalue reference overload for non-scalar <tt class="docutils literal">T</tt>, the
|
|
nested <tt class="docutils literal">qualifier</tt> type of <tt class="docutils literal">Tag</tt> must be <tt class="docutils literal">in_reference</tt>.</li>
|
|
<li>To use the mutable rvalue reference overload for non-scalar <tt class="docutils literal">T</tt>, the
|
|
nested <tt class="docutils literal">qualifier</tt> type of <tt class="docutils literal">Tag</tt> must be <tt class="docutils literal">consume_reference</tt> or
|
|
<tt class="docutils literal">move_from_reference</tt>.</li>
|
|
</ul>
|
|
<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">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">value</tt> with <a class="reference internal" href="#kw">keyword</a> <tt class="docutils literal">Tag</tt></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p id="bitwise-or-operator"><tt class="docutils literal">operator|</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">Synopsis:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<pre class="literal-block">
|
|
template <typename T>
|
|
constexpr <em>tagged default</em> operator|(T const& x) const;
|
|
|
|
template <typename T>
|
|
constexpr <em>tagged default</em> operator|(T& x) const;
|
|
|
|
template <typename T>
|
|
constexpr <em>tagged default</em> operator|(T const&& x) const;
|
|
|
|
template <typename T>
|
|
constexpr <em>tagged default</em> operator|(T&& x) 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">one of the following:</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<ul class="simple">
|
|
<li>The nested <tt class="docutils literal">qualifier</tt> type of <tt class="docutils literal">Tag</tt> must be <tt class="docutils literal">forward_reference</tt>.</li>
|
|
<li>To use the <tt class="docutils literal">const</tt> lvalue reference overload, <tt class="docutils literal">T</tt> must be scalar, or
|
|
the nested <tt class="docutils literal">qualifier</tt> type of <tt class="docutils literal">Tag</tt> must be <tt class="docutils literal">in_reference</tt>.</li>
|
|
<li>To use the mutable lvalue reference overload, the nested <tt class="docutils literal">qualifier</tt>
|
|
type of <tt class="docutils literal">Tag</tt> must be <tt class="docutils literal">out_reference</tt> or <tt class="docutils literal">in_out_reference</tt>, and
|
|
<tt class="docutils literal">T</tt> must not be <tt class="docutils literal">const</tt>-qualified.</li>
|
|
<li>To use the <tt class="docutils literal">const</tt> rvalue reference overload for non-scalar <tt class="docutils literal">T</tt>, the
|
|
nested <tt class="docutils literal">qualifier</tt> type of <tt class="docutils literal">Tag</tt> must be <tt class="docutils literal">in_reference</tt>.</li>
|
|
<li>To use the mutable rvalue reference overload for non-scalar <tt class="docutils literal">T</tt>, the
|
|
nested <tt class="docutils literal">qualifier</tt> type of <tt class="docutils literal">Tag</tt> must be <tt class="docutils literal">consume_reference</tt> or
|
|
<tt class="docutils literal">move_from_reference</tt>.</li>
|
|
</ul>
|
|
<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">a <a class="reference internal" href="#tagged-default">tagged default</a> with <em>value</em> <tt class="docutils literal">x</tt> and <a class="reference internal" href="#kw">keyword</a> <tt class="docutils literal">Tag</tt>.</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p id="logical-or-operator"><tt class="docutils literal">operator||</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">Synopsis:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<pre class="literal-block">
|
|
template <typename F>
|
|
constexpr <em>tagged lazy default</em> operator||(F const& g) const;
|
|
|
|
template <typename F>
|
|
constexpr <em>tagged lazy default</em> operator||(F& g) 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">g()</tt> must be valid, with type
|
|
<a class="reference external" href="../../../utility/utility.htm#result_of"><tt class="docutils literal"><span class="pre">boost::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="id6"><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">g</tt> and <a class="reference internal" href="#kw">keyword</a> <tt class="docutils literal">Tag</tt>.</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p id="instance"><tt class="docutils literal">instance</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">Synopsis:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<pre class="literal-block">
|
|
static keyword<Tag> const& instance;
|
|
</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">Returns:</th><td class="field-body">a “singleton instance”: the same object will be returned on each
|
|
invocation of <tt class="docutils literal">instance</tt>.</td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Thread Safety:</th><td class="field-body"><tt class="docutils literal">instance</tt> can be accessed from multiple threads simultaneously.</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p id="get"><tt class="docutils literal">get</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">Synopsis:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<pre class="literal-block">
|
|
static keyword<Tag>& get();
|
|
</pre>
|
|
<div class="admonition-deprecated admonition">
|
|
<p class="first admonition-title">Deprecated</p>
|
|
<p class="last">This function has been deprecated in favor of <tt class="docutils literal">instance</tt>.</p>
|
|
</div>
|
|
<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">a “singleton instance”: the same object will be returned on each
|
|
invocation of <tt class="docutils literal">get()</tt>.</td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Thread Safety:</th><td class="field-body"><tt class="docutils literal">get()</tt> can be called from multiple threads simultaneously.</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
<div class="section" id="id7">
|
|
<span id="template-keyword"></span><h2><a class="toc-backref" href="#id42">4.2 <tt class="docutils literal">template_keyword</tt></a></h2>
|
|
<p>This class template encapsulates a named template parameter. Every type
|
|
generated by the <a class="reference internal" href="#boost-parameter-template-keyword"><tt class="docutils literal">BOOST_PARAMETER_TEMPLATE_KEYWORD</tt></a> macro is a specialization
|
|
of <tt class="docutils literal">template_keyword</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/template_keyword.hpp">boost/parameter/template_keyword.hpp</a></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<pre class="literal-block">
|
|
template <typename Tag, typename T>
|
|
struct template_keyword
|
|
{
|
|
typedef Tag key_type;
|
|
typedef T value_type;
|
|
typedef <em>implementation defined</em> reference;
|
|
};
|
|
</pre>
|
|
<p>The <a class="reference external" href="../../test/ntp.cpp">test/ntp.cpp</a> test program demonstrates proper usage of this class template.</p>
|
|
</div>
|
|
<div class="section" id="id8">
|
|
<span id="parameters"></span><h2><a class="toc-backref" href="#id43">4.3 <tt class="docutils literal">parameters</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">parameters</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 <typename ...PSpec>
|
|
struct parameters
|
|
{
|
|
template <typename ...Args>
|
|
struct <a class="reference internal" href="#match"><tt class="docutils literal">match</tt></a>
|
|
{
|
|
typedef … type;
|
|
};
|
|
|
|
template <typename ...Args>
|
|
<a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> <a class="reference internal" href="#function-call-operator"><tt class="docutils literal">operator()</tt></a>(Args&&... args) 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">Each element in the <tt class="docutils literal">PSpec</tt> parameter pack must be a model 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">R</tt> ## <em>i</em> and <tt class="docutils literal">K</tt> ## <em>i</em> are defined as
|
|
follows, for any argument type <tt class="docutils literal">A</tt> ## <em>i</em>:</p>
|
|
<div class="last line-block">
|
|
<div class="line">let <tt class="docutils literal">D0</tt> the set [d0, …, d ## <em>j</em>] of all <strong>deduced</strong></div>
|
|
<div class="line"><em>parameter specs</em> in the <tt class="docutils literal">PSpec</tt> parameter pack</div>
|
|
<div class="line"><tt class="docutils literal">R</tt> ## <em>i</em> is the <a class="reference internal" href="#intended-argument-type">intended argument type</a> of <tt class="docutils literal">A</tt> ## <em>i</em></div>
|
|
<div class="line"><br /></div>
|
|
<div class="line">if <tt class="docutils literal">A</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="#assignment-operator"><tt class="docutils literal">operator=</tt></a></div>
|
|
<div class="line">then</div>
|
|
<div class="line-block">
|
|
<div class="line"><tt class="docutils literal">K</tt> ## <em>i</em> is <tt class="docutils literal">T</tt></div>
|
|
</div>
|
|
<div class="line">else</div>
|
|
<div class="line-block">
|
|
<div class="line">if some <tt class="docutils literal">A</tt> ## <em>j</em> where <em>j</em> ≤ <em>i</em> is a result type of</div>
|
|
<div class="line"><tt class="docutils literal"><span class="pre">keyword<T>::</span></tt> <a class="reference internal" href="#assignment-operator"><tt class="docutils literal">operator=</tt></a></div>
|
|
<div class="line"><em>or</em> some <tt class="docutils literal">P</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">d</tt> ## <em>j</em> in <tt class="docutils literal">D</tt> ## <em>i</em></div>
|
|
<div class="line">matches <tt class="docutils literal">A</tt> ## <em>i</em></div>
|
|
<div class="line">then</div>
|
|
<div class="line-block">
|
|
<div class="line"><tt class="docutils literal">K</tt> ## <em>i</em> is the <a class="reference internal" href="#keyword-tag-type">keyword tag type</a> of <tt class="docutils literal">d</tt> ## <em>j</em>.</div>
|
|
<div class="line"><tt class="docutils literal">D</tt><sub>i+1</sub> is <tt class="docutils literal">D</tt> ## <em>i</em> - [ <tt class="docutils literal">d</tt> ## <em>j</em>]</div>
|
|
</div>
|
|
</div>
|
|
<div class="line">else</div>
|
|
<div class="line-block">
|
|
<div class="line"><tt class="docutils literal">K</tt> ## <em>i</em> is the <a class="reference internal" href="#keyword-tag-type">keyword tag type</a> of <tt class="docutils literal">P</tt> ## <em>i</em>.</div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
<dl class="docutils" id="match">
|
|
<dt><tt class="docutils literal">match</tt></dt>
|
|
<dd>A <a class="reference external" href="../../../mpl/doc/refmanual/metafunction.html">Metafunction</a> used to remove a <a class="reference external" href="index.html#forwarding-functions">forwarding function</a> from overload
|
|
resolution.</dd>
|
|
</dl>
|
|
<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 all elements in <tt class="docutils literal"><span class="pre">Params...</span></tt> are <em>satisfied</em> (see below), then
|
|
<tt class="docutils literal"><span class="pre">parameters<Params...></span></tt>. Otherwise, <tt class="docutils literal"><span class="pre">match<Args...>::type</span></tt> is not
|
|
defined.</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>Each element <tt class="docutils literal">P</tt> in <tt class="docutils literal"><span class="pre">Params...</span></tt> is <strong>satisfied</strong> if either:</p>
|
|
<ul>
|
|
<li><p class="first"><tt class="docutils literal">P</tt> is the <em>unspecified</em> default</p>
|
|
</li>
|
|
<li><p class="first"><strong>or</strong>, <tt class="docutils literal">P</tt> is a <em>keyword tag type</em></p>
|
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</li>
|
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<li><dl class="first docutils">
|
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<dt><strong>or</strong>, <tt class="docutils literal">P</tt> is <a class="reference internal" href="#optional"><tt class="docutils literal">optional</tt></a> <tt class="docutils literal"><X,F></tt> and either</dt>
|
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<dd><ul class="first last">
|
|
<li><p class="first"><tt class="docutils literal">X</tt> is not <tt class="docutils literal">K</tt> ## <em>i</em> for any <em>i</em>,</p>
|
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</li>
|
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<li><dl class="first docutils">
|
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<dt><strong>or</strong> <tt class="docutils literal">X</tt> is some <tt class="docutils literal">K</tt> ## <em>i</em> and <tt class="docutils literal"><span class="pre">mpl::apply<F,R</span></tt> ## <em>i</em></dt>
|
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<dd><p class="first last"><tt class="docutils literal"><span class="pre">>::type::value</span></tt> is <tt class="docutils literal">true</tt></p>
|
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</dd>
|
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</dl>
|
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</li>
|
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</ul>
|
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</dd>
|
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</dl>
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</li>
|
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<li><dl class="first docutils">
|
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<dt><strong>or</strong>, <tt class="docutils literal">P</tt> is <a class="reference internal" href="#required"><tt class="docutils literal">required</tt></a> <tt class="docutils literal"><X,F></tt>, and</dt>
|
|
<dd><ul class="first last simple">
|
|
<li><tt class="docutils literal">X</tt> is some <tt class="docutils literal">K</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">true</tt></li>
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</ul>
|
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</dd>
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</dl>
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</li>
|
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</ul>
|
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<p id="function-call-operator"><tt class="docutils literal">operator()</tt></p>
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<table class="docutils field-list" frame="void" rules="none">
|
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<col class="field-name" />
|
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<col class="field-body" />
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<tbody valign="top">
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<tr class="field"><th class="field-name">Synopsis:</th><td class="field-body"></td>
|
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</tr>
|
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</tbody>
|
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</table>
|
|
<pre class="literal-block">
|
|
template <typename ...Args>
|
|
<a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> operator()(Args&&... args) const;
|
|
</pre>
|
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<table class="docutils field-list" frame="void" rules="none">
|
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<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">a</tt> ## <em>i</em>,</p>
|
|
<ul class="last">
|
|
<li><p class="first">if <tt class="docutils literal">a</tt> ## <em>i</em> is a single-element <span class="concept">ArgumentPack</span>, its element</p>
|
|
</li>
|
|
<li><dl class="first docutils">
|
|
<dt>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">K</tt> ## <em>i</em> and <em>value</em></dt>
|
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<dd><p class="first last"><tt class="docutils literal">a</tt> ## <em>i</em></p>
|
|
</dd>
|
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</dl>
|
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</li>
|
|
</ul>
|
|
</td>
|
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</tr>
|
|
</tbody>
|
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</table>
|
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</div>
|
|
<div class="section" id="optional-required">
|
|
<span id="required"></span><span id="optional"></span><h2><a class="toc-backref" href="#id44">4.4 <tt class="docutils literal">optional</tt>, <tt class="docutils literal">required</tt></a></h2>
|
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<p>These templates describe the requirements on a function parameter.</p>
|
|
<p><tt class="docutils literal">optional</tt> is defined in: <a class="reference external" href="../../../../boost/parameter/optional.hpp">boost/parameter/optional.hpp</a></p>
|
|
<p><tt class="docutils literal">required</tt> is defined in: <a class="reference external" href="../../../../boost/parameter/required.hpp">boost/parameter/required.hpp</a></p>
|
|
<p>Both headers are included by: <a class="reference external" href="../../../../boost/parameter/preprocessor.hpp">boost/parameter/preprocessor.hpp</a></p>
|
|
<table class="docutils field-list" frame="void" rules="none">
|
|
<col class="field-name" />
|
|
<col class="field-body" />
|
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<tbody valign="top">
|
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<tr class="field"><th class="field-name" colspan="2">Specializations model:</th></tr>
|
|
<tr class="field"><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 <typename Tag, typename Predicate = <em>unspecified</em>>
|
|
struct optional;
|
|
|
|
template <typename Tag, typename Predicate = <em>unspecified</em>>
|
|
struct required;
|
|
</pre>
|
|
<p>The default value of <tt class="docutils literal">Predicate</tt> is an unspecified <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary Metafunction
|
|
Class</a> that returns <tt class="docutils literal"><span class="pre">mpl::true_</span></tt> for any argument. If
|
|
<a class="reference internal" href="#boost-parameter-can-use-mp11"><tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt></a> is defined, then the default value of
|
|
<tt class="docutils literal">Predicate</tt> is also a <a class="reference external" href="../../../mp11/doc/html/mp11.html">Boost.MP11</a>-style quoted metafunction that returns
|
|
<tt class="docutils literal"><span class="pre">mp11::mp_true</span></tt> for any argument.</p>
|
|
</div>
|
|
<div class="section" id="id9">
|
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<span id="deduced"></span><h2><a class="toc-backref" href="#id45">4.5 <tt class="docutils literal">deduced</tt></a></h2>
|
|
<p>This template is used to wrap the <em>keyword tag</em> argument to
|
|
<tt class="docutils literal">optional</tt> or <tt class="docutils literal">required</tt>.</p>
|
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<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/deduced.hpp">boost/parameter/deduced.hpp</a></td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Included by:</th><td class="field-body"><a class="reference external" href="../../../../boost/parameter/preprocessor.hpp">boost/parameter/preprocessor.hpp</a></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
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<pre class="literal-block">
|
|
template <typename Tag>
|
|
struct deduced;
|
|
</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">nothing</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
</div>
|
|
<hr class="docutils" />
|
|
<div class="section" id="metafunctions">
|
|
<h1><a class="toc-backref" href="#id46">5 Metafunctions</a></h1>
|
|
<p>A <a class="reference external" href="../../../mpl/doc/refmanual/metafunction.html">Metafunction</a> is conceptually a function that operates on, and returns,
|
|
C++ types.</p>
|
|
<div class="section" id="id10">
|
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<span id="binding"></span><h2><a class="toc-backref" href="#id47">5.1 <tt class="docutils literal">binding</tt></a></h2>
|
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<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>
|
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<table class="docutils field-list" frame="void" rules="none">
|
|
<col class="field-name" />
|
|
<col class="field-body" />
|
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<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 <typename A, typename K, typename 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">A</tt> must be 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">A</tt> having
|
|
<a class="reference internal" href="#keyword-tag-type">keyword tag type</a> <tt class="docutils literal">K</tt>, if any. If no such <a class="reference internal" href="#tagged-reference">tagged reference</a> exists,
|
|
returns <tt class="docutils literal">D</tt>.</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
<div class="section" id="id11">
|
|
<span id="lazy-binding"></span><h2><a class="toc-backref" href="#id48">5.2 <tt class="docutils literal">lazy_binding</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 <typename A, typename K, typename 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">A</tt> must be 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">A</tt> having
|
|
<a class="reference internal" href="#keyword-tag-type">keyword tag type</a> <tt class="docutils literal">K</tt>, if any. If no such <a class="reference internal" href="#tagged-reference">tagged reference</a> exists,
|
|
returns <a class="reference external" href="../../../utility/utility.htm#result_of"><tt class="docutils literal"><span class="pre">boost::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="id12"><sup>2</sup></a></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
<div class="section" id="id13">
|
|
<span id="value-type"></span><h2><a class="toc-backref" href="#id49">5.3 <tt class="docutils literal">value_type</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 in:</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 <typename A, typename K, typename 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">A</tt> must be 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 (possibly const-qualified) type of the <a class="reference internal" href="#tagged-reference">tagged reference</a> in
|
|
<tt class="docutils literal">A</tt> having <a class="reference internal" href="#keyword-tag-type">keyword tag type</a> <tt class="docutils literal">K</tt>, if any. If no such
|
|
<a class="reference internal" href="#tagged-reference">tagged reference</a> exists, returns <tt class="docutils literal">D</tt>. Equivalent to:</p>
|
|
<pre class="literal-block">
|
|
typename <a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/remove_reference.html">boost::remove_reference</a><
|
|
typename <a class="reference internal" href="#binding"><tt class="docutils literal">binding</tt></a><A, K, D>::type
|
|
>::type
|
|
</pre>
|
|
<p class="last">… when <tt class="docutils literal">D</tt> is not a reference type.</p>
|
|
</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
<div class="section" id="id14">
|
|
<span id="lazy-value-type"></span><h2><a class="toc-backref" href="#id50">5.4 <tt class="docutils literal">lazy_value_type</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/value_type.hpp">boost/parameter/value_type.hpp</a></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<pre class="literal-block">
|
|
template <typename A, typename K, typename F>
|
|
struct lazy_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"><tt class="docutils literal">A</tt> must be 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 (possibly const-qualified) type of the <a class="reference internal" href="#tagged-reference">tagged reference</a> in
|
|
<tt class="docutils literal">A</tt> having <a class="reference internal" href="#keyword-tag-type">keyword tag type</a> <tt class="docutils literal">K</tt>, if any. If no such
|
|
<a class="reference internal" href="#tagged-reference">tagged reference</a> exists, returns
|
|
<a class="reference external" href="../../../utility/utility.htm#result_of"><tt class="docutils literal"><span class="pre">boost::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="id15"><sup>2</sup></a></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
<div class="section" id="id16">
|
|
<span id="are-tagged-arguments"></span><h2><a class="toc-backref" href="#id51">5.5 <tt class="docutils literal">are_tagged_arguments</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/are_tagged_arguments.hpp">boost/parameter/are_tagged_arguments.hpp</a></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<pre class="literal-block">
|
|
template <typename T0, typename ...Pack>
|
|
struct are_tagged_arguments
|
|
// : <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> if T0 and all elements in Pack are
|
|
// tagged reference types, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::false_</a> otherwise.
|
|
{
|
|
};
|
|
</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">Returns:</th><td class="field-body"><tt class="docutils literal"><span class="pre">mpl::true_</span></tt> if <tt class="docutils literal">T0</tt> and all elements in parameter pack <tt class="docutils literal">Pack</tt> are
|
|
<a class="reference internal" href="#tagged-reference">tagged reference</a> types, <tt class="docutils literal"><span class="pre">mpl::false_</span></tt> otherwise.</td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Example usage:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>When implementing a Boost.Parameter-enabled constructor for a container that
|
|
conforms to the C++ standard, one needs to remember that the standard requires
|
|
the presence of other constructors that are typically defined as templates,
|
|
such as range constructors. To avoid overload ambiguities between the two
|
|
constructors, use this metafunction in conjunction with <tt class="docutils literal">disable_if</tt> to
|
|
define the range constructor.</p>
|
|
<pre class="literal-block">
|
|
template <typename B>
|
|
class frontend : public B
|
|
{
|
|
struct _enabler
|
|
{
|
|
};
|
|
|
|
public:
|
|
<a class="reference internal" href="#boost-parameter-no-spec-constructor"><tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_CONSTRUCTOR</tt></a>(frontend, (B))
|
|
|
|
template <typename Iterator>
|
|
frontend(
|
|
Iterator itr
|
|
, Iterator itr_end
|
|
, typename <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if</a><
|
|
are_tagged_arguments<Iterator>
|
|
, _enabler
|
|
>::type = _enabler()
|
|
) : B(itr, itr_end)
|
|
{
|
|
}
|
|
};
|
|
</pre>
|
|
</div>
|
|
<div class="section" id="id17">
|
|
<span id="is-argument-pack"></span><h2><a class="toc-backref" href="#id52">5.6 <tt class="docutils literal">is_argument_pack</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/is_argument_pack.hpp">boost/parameter/is_argument_pack.hpp</a></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<pre class="literal-block">
|
|
template <typename T>
|
|
struct is_argument_pack
|
|
// : <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> if T is a model of <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>,
|
|
// <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::false_</a> otherwise.
|
|
{
|
|
};
|
|
</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">Returns:</th><td class="field-body"><tt class="docutils literal"><span class="pre">mpl::true_</span></tt> if <tt class="docutils literal">T</tt> is a model of <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>, <tt class="docutils literal"><span class="pre">mpl::false_</span></tt>
|
|
otherwise.</td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Example usage:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>To avoid overload ambiguities between a constructor that takes in an
|
|
<a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> and a templated conversion constructor, use this
|
|
metafunction in conjunction with <tt class="docutils literal">enable_if</tt>.</p>
|
|
<pre class="literal-block">
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>(a0)
|
|
|
|
template <typename T>
|
|
class backend0
|
|
{
|
|
struct _enabler
|
|
{
|
|
};
|
|
|
|
T a0;
|
|
|
|
public:
|
|
template <typename ArgPack>
|
|
explicit backend0(
|
|
ArgPack const& args
|
|
, typename <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a><
|
|
is_argument_pack<ArgPack>
|
|
, _enabler
|
|
>::type = _enabler()
|
|
) : a0(args[_a0])
|
|
{
|
|
}
|
|
|
|
template <typename U>
|
|
backend0(
|
|
backend0<U> const& copy
|
|
, typename <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_convertible.html">boost::is_convertible</a><U,T>
|
|
, _enabler
|
|
>::type = _enabler()
|
|
) : a0(copy.get_a0())
|
|
{
|
|
}
|
|
|
|
T const& get_a0() const
|
|
{
|
|
return this->a0;
|
|
}
|
|
};
|
|
</pre>
|
|
</div>
|
|
<div class="section" id="id18">
|
|
<span id="result-of-compose"></span><h2><a class="toc-backref" href="#id53">5.7 <tt class="docutils literal"><span class="pre">result_of::compose</span></tt></a></h2>
|
|
<p>Returns the result type of the <a class="reference internal" href="#compose"><tt class="docutils literal">compose</tt></a> function.</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/compose.hpp">boost/parameter/compose.hpp</a></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<pre class="literal-block">
|
|
template <typename ...TaggedArgs>
|
|
struct compose
|
|
: <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a><
|
|
<a class="reference internal" href="#are-tagged-arguments"><tt class="docutils literal">are_tagged_arguments</tt></a><T0,Pack...>
|
|
, <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>
|
|
>
|
|
{
|
|
};
|
|
|
|
template <>
|
|
struct compose<>
|
|
{
|
|
typedef <em>empty</em> <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> 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">All elements in <tt class="docutils literal">TaggedArgs</tt> must be <a class="reference internal" href="#tagged-reference">tagged reference</a> types, if
|
|
specified.</td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Returns:</th><td class="field-body">the result type of the <a class="reference internal" href="#compose"><tt class="docutils literal">compose</tt></a> function.</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
</div>
|
|
<hr class="docutils" />
|
|
<div class="section" id="function-templates">
|
|
<h1><a class="toc-backref" href="#id54">6 Function Templates</a></h1>
|
|
<div class="section" id="id19">
|
|
<span id="compose"></span><h2><a class="toc-backref" href="#id55">6.1 <tt class="docutils literal">compose</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/compose.hpp">boost/parameter/compose.hpp</a></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<pre class="literal-block">
|
|
template <typename ...Pack>
|
|
constexpr typename <a class="reference internal" href="#result-of-compose"><tt class="docutils literal"><span class="pre">result_of::compose</span></tt></a><Pack...>::type
|
|
compose(Pack const&... args);
|
|
</pre>
|
|
<p>This function facilitates easier variadic argument composition. It is used by
|
|
the <a class="reference internal" href="#boost-parameter-no-spec-function"><tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_FUNCTION</tt></a>,
|
|
<a class="reference internal" href="#boost-parameter-no-spec-member-function"><tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_MEMBER_FUNCTION</tt></a>,
|
|
<a class="reference internal" href="#boost-parameter-no-spec-const-member-function"><tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_CONST_MEMBER_FUNCTION</tt></a>,
|
|
<a class="reference internal" href="#boost-parameter-no-spec-function-call-operator"><tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_FUNCTION_CALL_OPERATOR</tt></a>,
|
|
<a class="reference internal" href="#boost-parameter-no-spec-const-function-call-operator"><tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_CONST_FUNCTION_CALL_OPERATOR</tt></a>,
|
|
<a class="reference internal" href="#boost-parameter-no-spec-constructor"><tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_CONSTRUCTOR</tt></a>, and
|
|
<a class="reference internal" href="#boost-parameter-no-spec-no-base-constructor"><tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_NO_BASE_CONSTRUCTOR</tt></a> code generation macros. You
|
|
can use it to write your own code generation macros if the ones provided by
|
|
this library do not suffice.</p>
|
|
<p>Unlike the <a class="reference internal" href="#tagged-reference">tagged reference</a> comma operator, the <tt class="docutils literal">compose()</tt> function is
|
|
variadic, as mentioned before. However, the <a class="reference internal" href="#tagged-reference">tagged reference</a> comma operator
|
|
can be invoked indefinitely and therefore does not limit the size of the
|
|
resulting <span class="concept">ArgumentPack</span>, while the <tt class="docutils literal">compose()</tt> function cannot take in more
|
|
than <a class="reference internal" href="#boost-parameter-compose-max-arity"><tt class="docutils literal">BOOST_PARAMETER_COMPOSE_MAX_ARITY</tt></a> arguments for compilers that do not
|
|
support perfect forwarding.</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">Requires:</th><td class="field-body">All elements in <tt class="docutils literal">args</tt> must be <a class="reference internal" href="#tagged-reference">tagged reference</a> objects, if
|
|
specified.</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 all elements in <tt class="docutils literal">args</tt>, if
|
|
specified; an empty <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> otherwise.</td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Example usage:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<pre class="literal-block">
|
|
BOOST_PARAMETER_NAME(index)
|
|
BOOST_PARAMETER_NAME(name)
|
|
|
|
template <typename ArgumentPack>
|
|
int print_name_and_index(ArgumentPack const& args)
|
|
{
|
|
std::cout << "index = " << args[_index];
|
|
std::cout << "name = " << args[_name];
|
|
std::cout << "; " << std::endl;
|
|
return 0;
|
|
}
|
|
|
|
int y = print_name_and_index(compose(_index = 3, _name = "jones"));
|
|
</pre>
|
|
<p>The <a class="reference external" href="../../test/compose.cpp">compose.cpp</a> test program shows more examples using this function.</p>
|
|
</div>
|
|
</div>
|
|
<hr class="docutils" />
|
|
<div class="section" id="code-generation-macros">
|
|
<h1><a class="toc-backref" href="#id56">7 Code Generation Macros</a></h1>
|
|
<p>Macros in this section can be used to ease the writing of code
|
|
using the Parameter library by eliminating repetitive boilerplate.</p>
|
|
<div class="section" id="boost-parameter-function-result-name-tag-namespace-arguments">
|
|
<span id="boost-parameter-function"></span><h2><a class="toc-backref" href="#id57">7.1 <tt class="docutils literal">BOOST_PARAMETER_FUNCTION(result, name, tag_namespace, arguments)</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>
|
|
<p>Generates a function that can take in positional arguments, composed
|
|
arguments, named arguments, and deduced 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">Example usage:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>The return type of each of the following function templates falls under a
|
|
different value category.</p>
|
|
<pre class="literal-block">
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> rvalue_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const rvalue_const_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>& lvalue_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> lset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return lset;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const& lvalue_const_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const clset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return clset;
|
|
}
|
|
</pre>
|
|
<p>The <tt class="docutils literal"><span class="pre">U::evaluate_category</span></tt> static member function template has a simple job:
|
|
to return the correct value category when passed in an object returned by one
|
|
of the functions defined above. Assume that
|
|
<a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> is defined.</p>
|
|
<pre class="literal-block">
|
|
enum invoked
|
|
{
|
|
passed_by_lvalue_reference_to_const
|
|
, passed_by_lvalue_reference
|
|
, passed_by_rvalue_reference_to_const
|
|
, passed_by_rvalue_reference
|
|
};
|
|
|
|
struct U
|
|
{
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&)
|
|
{
|
|
return passed_by_lvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&)
|
|
{
|
|
return passed_by_lvalue_reference;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&&)
|
|
{
|
|
return passed_by_rvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&&)
|
|
{
|
|
return passed_by_rvalue_reference;
|
|
}
|
|
};
|
|
</pre>
|
|
<p>Define the named parameters that will comprise the argument specification that
|
|
this macro will use. Ensure that all their tag types are in the same
|
|
namespace, which is <tt class="docutils literal">kw</tt> in this case. The identifiers with leading
|
|
underscores can be passed to the bracket operator of <tt class="docutils literal">args</tt> to extract the
|
|
same argument to which the corresponding named parameter (without underscores)
|
|
is bound, as will be shown later.</p>
|
|
<pre class="literal-block">
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lrc, kw) in(lrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lr, kw) in_out(lr))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rrc, kw) in(rrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rr, kw) consume(rr))
|
|
</pre>
|
|
<p>Use the macro as a substitute for a normal function header. Enclose the
|
|
return type <tt class="docutils literal">bool</tt> in parentheses. For each parameter, also enclose the
|
|
expected value type in parentheses. Since the value types are mutually
|
|
exclusive, you can wrap the parameters in a <tt class="docutils literal">(deduced …)</tt>
|
|
clause. Otherwise, just as with a normal function, the order in which you
|
|
specify the parameters determines their position. Also, just as with a normal
|
|
function, optional parameters have default values, whereas required parameters
|
|
do not. Within the function body, either simply use the parameter name or
|
|
pass the matching identifier with the leading underscore to the bracket
|
|
operator of <tt class="docutils literal">args</tt> to extract the corresponding argument. Note that the
|
|
second method doesn't require <tt class="docutils literal"><span class="pre">std::forward</span></tt> to preserve value categories.</p>
|
|
<pre class="literal-block">
|
|
BOOST_PARAMETER_FUNCTION((bool), evaluate, kw,
|
|
(deduced
|
|
(required
|
|
(lrc, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><1>))
|
|
(lr, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><2>))
|
|
)
|
|
(optional
|
|
(rrc, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><3>), rvalue_const_bitset<2>())
|
|
(rr, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><4>), rvalue_bitset<3>())
|
|
)
|
|
)
|
|
)
|
|
{
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference_to_const
|
|
, U::evaluate_category<0>(lrc)
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference
|
|
, U::evaluate_category<1>(lr)
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference_to_const
|
|
, U::evaluate_category<2>(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><rrc0_type>(rrc0))
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference
|
|
, U::evaluate_category<3>(args[_rr0])
|
|
);
|
|
|
|
return true;
|
|
}
|
|
</pre>
|
|
<p>The following function calls are legal.</p>
|
|
<pre class="literal-block">
|
|
evaluate( // positional arguments
|
|
lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
, rvalue_const_bitset<2>()
|
|
, rvalue_bitset<3>()
|
|
);
|
|
evaluate( // positional arguments
|
|
lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
);
|
|
evaluate(( // composed arguments
|
|
_rr0 = rvalue_bitset<3>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
, _lr0 = lvalue_bitset<1>()
|
|
, _rrc0 = rvalue_const_bitset<2>()
|
|
));
|
|
evaluate( // named arguments
|
|
_rr0 = rvalue_bitset<3>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
, _lr0 = lvalue_bitset<1>()
|
|
, _rrc0 = rvalue_const_bitset<2>()
|
|
);
|
|
evaluate( // named arguments
|
|
_lr0 = lvalue_bitset<1>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
);
|
|
</pre>
|
|
<p>Because the parameters were wrapped in a <tt class="docutils literal">(deduced …)</tt> clause, the following
|
|
function calls are also legal.</p>
|
|
<pre class="literal-block">
|
|
evaluate( // deduced arguments
|
|
rvalue_bitset<3>()
|
|
, lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
, rvalue_const_bitset<2>()
|
|
);
|
|
evaluate( // deduced arguments
|
|
lvalue_bitset<1>()
|
|
, lvalue_const_bitset<0>()
|
|
);
|
|
</pre>
|
|
<p>The <a class="reference external" href="../../test/preprocessor.cpp">preprocessor.cpp</a>, <a class="reference external" href="../../test/preprocessor_deduced.cpp">preprocessor_deduced.cpp</a>, and
|
|
<a class="reference external" href="../../test/preprocessor_eval_category.cpp">preprocessor_eval_category.cpp</a> test programs demonstrate proper usage of this
|
|
macro.</p>
|
|
<p><strong>Macro parameters:</strong></p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">result</tt> is the parenthesized return type of the function.</li>
|
|
<li><tt class="docutils literal">name</tt> is the base name of the function; it determines the name of the
|
|
generated forwarding functions.</li>
|
|
<li><tt class="docutils literal">tag_namespace</tt> is the namespace in which the keywords used by the
|
|
function resides.</li>
|
|
<li><tt class="docutils literal">arguments</tt> is a <a class="reference external" href="../../../preprocessor/doc/index.html">Boost.Preprocessor</a> <a class="reference external" href="../../../preprocessor/doc/data/sequences.html">sequence</a> of
|
|
<em>argument-specifiers</em>, as defined below.</li>
|
|
</ul>
|
|
<p><strong>Argument specifiers syntax:</strong></p>
|
|
<pre class="literal-block">
|
|
argument-specifiers ::= <em>specifier-group0</em> {<em>specifier-group0</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>argument-name</em> '<strong>,</strong>' <em>restriction</em> '<strong>,</strong>' <em>default-value</em>
|
|
')'
|
|
|
|
required-specifier ::=
|
|
'<strong>(</strong>' <em>argument-name</em> '<strong>,</strong>' <em>restriction</em> ')'
|
|
|
|
restriction ::=
|
|
( '<strong>*</strong>' '<strong>(</strong>' <em>mfc</em> '<strong>)</strong>' ) |
|
|
( '<strong>(</strong>' <em>type-name</em> '<strong>)</strong>' ) |
|
|
'<strong>*</strong>'
|
|
</pre>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal"><span class="pre">argument-name</span></tt> is any valid C++ identifier.</li>
|
|
<li><tt class="docutils literal"><span class="pre">default-value</span></tt> is any valid C++ expression; if necessary, user code can
|
|
compute it in terms of <tt class="docutils literal"><span class="pre">previous-name</span> ## _type</tt>, where <tt class="docutils literal"><span class="pre">previous-name</span></tt>
|
|
is the <tt class="docutils literal"><span class="pre">argument-name</span></tt> in a previous <tt class="docutils literal"><span class="pre">specifier-group0</span></tt> or
|
|
<tt class="docutils literal"><span class="pre">specifier-group1</span></tt>. <em>This expression will be invoked exactly once.</em></li>
|
|
<li><tt class="docutils literal">mfc</tt> is an <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary Metafunction Class</a> whose first argument will
|
|
be the type of the corresponding <tt class="docutils literal"><span class="pre">argument-name</span></tt>, whose second argument
|
|
will be the entire <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>, and whose return type is a <a class="reference external" href="../../../mpl/doc/refmanual/integral-constant.html">Boolean
|
|
Integral Constant</a>; however, user code <em>cannot</em> compute <tt class="docutils literal">mfc</tt> in terms
|
|
of <tt class="docutils literal"><span class="pre">previous-name</span> ## _type</tt>.</li>
|
|
<li><tt class="docutils literal"><span class="pre">type-name</span></tt> is either the name of a <strong>target type</strong> or an <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary
|
|
Metafunction Class</a> whose first argument will be the type of the
|
|
corresponding <tt class="docutils literal"><span class="pre">argument-name</span></tt>, whose second argument will be the entire
|
|
<a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>, and whose return type is the <strong>target type</strong>. If
|
|
<tt class="docutils literal">restriction</tt> uses this form, then the type of the generated name
|
|
<tt class="docutils literal"><span class="pre">argument-name</span> ## _type</tt> will be computed in terms of the <strong>target
|
|
type</strong>, and the generated reference <tt class="docutils literal"><span class="pre">argument-name</span></tt> (but not its
|
|
corresponding entry in <tt class="docutils literal">args</tt>) will be cast to that type.</li>
|
|
</ul>
|
|
<p><strong>Approximate expansion:</strong></p>
|
|
<p>Where:</p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">n</tt> denotes the <em>minimum</em> arity, as determined from <tt class="docutils literal">arguments</tt>.</li>
|
|
<li><tt class="docutils literal">m</tt> denotes the <em>maximum</em> arity, as determined from <tt class="docutils literal">arguments</tt>.</li>
|
|
</ul>
|
|
<pre class="literal-block">
|
|
// If <strong>result</strong> is a template instantiation of <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if_c</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if_c</a>, or
|
|
// <a class="reference external" href="http://en.cppreference.com/w/cpp/types/enable_if">std::enable_if</a>:
|
|
template <typename Args>
|
|
using boost_param_result_ ## __LINE__ ## <strong>name</strong> = <strong>result</strong>;
|
|
|
|
// If <strong>result</strong> is a simple return type:
|
|
template <typename Args>
|
|
struct boost_param_result_ ## __LINE__ ## <strong>name</strong>
|
|
{
|
|
typedef <strong>result</strong> type;
|
|
};
|
|
|
|
struct boost_param_params_ ## __LINE__ ## <strong>name</strong>
|
|
: <a class="reference internal" href="#parameters"><tt class="docutils literal">parameters</tt></a><
|
|
<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 <typename Args>
|
|
typename boost_param_result_ ## __LINE__ ## <strong>name</strong><Args>::type
|
|
boost_param_impl ## __LINE__ ## <strong>name</strong>(Args const&);
|
|
|
|
template <typename A0, …, typename A ## <strong>n</strong>>
|
|
<strong>result</strong> <strong>name</strong>(
|
|
A0&& a0, …, A ## <strong>n</strong>&& a ## <strong>n</strong>
|
|
, typename boost_param_parameters_ ## __LINE__ ## <strong>name</strong>
|
|
::match<A0, …, A ## <strong>n</strong>>::type
|
|
= boost_param_parameters_ ## __LINE__ ## <strong>name</strong>()
|
|
)
|
|
{
|
|
return boost_param_impl ## __LINE__ ## <strong>name</strong>(
|
|
boost_param_parameters_ ## __LINE__ ## <strong>name</strong>()(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A0>(a0)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>n</strong>>(a ## <strong>n</strong>)
|
|
)
|
|
);
|
|
}
|
|
|
|
<span class="vellipsis">⋮</span>
|
|
|
|
template <typename A0, …, typename A ## <strong>m</strong>>
|
|
<strong>result</strong> <strong>name</strong>(
|
|
A0&& a0, …, A ## <strong>m</strong>&& a ## <strong>m</strong>
|
|
, typename boost_param_parameters_ ## __LINE__ ## <strong>name</strong>
|
|
::match<A0, …, A ## <strong>m</strong>>::type
|
|
= boost_param_parameters_ ## __LINE__ ## <strong>name</strong>()
|
|
)
|
|
{
|
|
return boost_param_impl ## __LINE__ ## <strong>name</strong>(
|
|
boost_param_parameters_ ## __LINE__ ## <strong>name</strong>()(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A0>(a0)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>m</strong>>(a ## <strong>m</strong>)
|
|
)
|
|
);
|
|
}
|
|
|
|
template <
|
|
typename ResultType
|
|
, typename Args
|
|
, typename <em>argument name</em> ## <strong>0</strong> ## _type
|
|
, …
|
|
, typename <em>argument name</em> ## <strong>n</strong> ## _type
|
|
>
|
|
ResultType
|
|
boost_param_dispatch_0boost_ ## __LINE__ ## <strong>name</strong>(
|
|
(ResultType(*)())
|
|
, Args const& args
|
|
, <em>argument name</em> ## <strong>0</strong> ## _type&& <em>argument name</em> ## <strong>0</strong>
|
|
, …
|
|
, <em>argument name</em> ## <strong>n</strong> ## _type&& <em>argument name</em> ## <strong>m</strong>
|
|
);
|
|
|
|
<span class="vellipsis">⋮</span>
|
|
|
|
template <
|
|
typename ResultType
|
|
, typename Args
|
|
, typename <em>argument name</em> ## <strong>0</strong> ## _type
|
|
, …
|
|
, typename <em>argument name</em> ## <strong>m</strong> ## _type
|
|
>
|
|
ResultType
|
|
boost_param_dispatch_0boost_ ## __LINE__ ## <strong>name</strong>(
|
|
(ResultType(*)())
|
|
, Args const& args
|
|
, <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>
|
|
);
|
|
|
|
template <typename Args>
|
|
typename boost_param_result_ ## __LINE__ ## <strong>name</strong><Args>::type
|
|
boost_param_impl ## __LINE__ ## <strong>name</strong>(Args const& args)
|
|
{
|
|
return boost_param_dispatch_0boost_ ## __LINE__ ## <strong>name</strong>(
|
|
static_cast<
|
|
typename boost_param_result_ ## __LINE__ ## <strong>name</strong><
|
|
Args
|
|
>::type(*)()
|
|
>(<a class="reference external" href="http://en.cppreference.com/w/cpp/language/nullptr">std::nullptr</a>)
|
|
, args
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><
|
|
typename <a class="reference internal" href="#value-type"><tt class="docutils literal">value_type</tt></a><
|
|
Args
|
|
, <em>keyword tag type of required parameter</em> ## <strong>0</strong>
|
|
>::type
|
|
>(args[ <em>keyword object of required parameter</em> ## <strong>0</strong>])
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><
|
|
typename <a class="reference internal" href="#value-type"><tt class="docutils literal">value_type</tt></a><
|
|
Args
|
|
, <em>keyword tag type of required parameter</em> ## <strong>n</strong>
|
|
>::type
|
|
>(args[ <em>keyword object of required parameter</em> ## <strong>n</strong>])
|
|
);
|
|
}
|
|
|
|
template <
|
|
typename ResultType
|
|
, typename Args
|
|
, typename <em>argument name</em> ## <strong>0</strong> ## _type
|
|
, …
|
|
, typename <em>argument name</em> ## <strong>n</strong> ## _type
|
|
>
|
|
ResultType
|
|
boost_param_dispatch_0boost_ ## __LINE__ ## <strong>name</strong>(
|
|
(ResultType(*)())
|
|
, Args const& args
|
|
, <em>argument name</em> ## <strong>0</strong> ## _type&& <em>argument name</em> ## <strong>0</strong>
|
|
, …
|
|
, <em>argument name</em> ## <strong>n</strong> ## _type&& <em>argument name</em> ## <strong>n</strong>
|
|
)
|
|
{
|
|
return boost_param_dispatch_0boost_ ## __LINE__ ## <strong>name</strong>(
|
|
static_cast<ResultType(*)()>(<a class="reference external" href="http://en.cppreference.com/w/cpp/language/nullptr">std::nullptr</a>)
|
|
, (args, <em>keyword object of optional parameter</em> ## <strong>n + 1</strong> =
|
|
<em>default value of optional parameter</em> ## <strong>n + 1</strong>
|
|
)
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><<em>argument name</em> ## <strong>0</strong> ## _type>(
|
|
<em>argument name</em> ## <strong>0</strong>
|
|
)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><<em>argument name</em> ## <strong>n</strong> ## _type>(
|
|
<em>argument name</em> ## <strong>n</strong>
|
|
)
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><
|
|
typename <a class="reference internal" href="#value-type"><tt class="docutils literal">value_type</tt></a><
|
|
Args
|
|
, <em>keyword tag type of optional parameter</em> ## <strong>n + 1</strong>
|
|
>::type
|
|
>(<em>default value of optional parameter</em> ## <strong>n + 1</strong>)
|
|
);
|
|
}
|
|
|
|
<span class="vellipsis">⋮</span>
|
|
|
|
template <
|
|
typename ResultType
|
|
, typename Args
|
|
, typename <em>argument name</em> ## <strong>0</strong> ## _type
|
|
, …
|
|
, typename <em>argument name</em> ## <strong>m</strong> ## _type
|
|
>
|
|
ResultType
|
|
boost_param_dispatch_0boost_ ## __LINE__ ## <strong>name</strong>(
|
|
(ResultType(*)())
|
|
, Args const& args
|
|
, <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>
|
|
</div>
|
|
<div class="section" id="boost-parameter-member-function-result-name-tag-namespace-arguments">
|
|
<span id="boost-parameter-member-function"></span><h2><a class="toc-backref" href="#id58">7.2 <tt class="docutils literal">BOOST_PARAMETER_MEMBER_FUNCTION(result, name, tag_namespace, arguments)</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>
|
|
<p>Generates a member function that can take in positional arguments, composed
|
|
arguments, named arguments, and deduced 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">Example usage:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>The return type of each of the following function templates falls under a
|
|
different value category.</p>
|
|
<pre class="literal-block">
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> rvalue_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const rvalue_const_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>& lvalue_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> lset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return lset;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const& lvalue_const_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const clset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return clset;
|
|
}
|
|
</pre>
|
|
<p>The <tt class="docutils literal"><span class="pre">U::evaluate_category</span></tt> static member function template has a simple job:
|
|
to return the correct value category when passed in an object returned by one
|
|
of the functions defined above. Assume that
|
|
<a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> is defined.</p>
|
|
<pre class="literal-block">
|
|
enum invoked
|
|
{
|
|
passed_by_lvalue_reference_to_const
|
|
, passed_by_lvalue_reference
|
|
, passed_by_rvalue_reference_to_const
|
|
, passed_by_rvalue_reference
|
|
};
|
|
|
|
struct U
|
|
{
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&)
|
|
{
|
|
return passed_by_lvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&)
|
|
{
|
|
return passed_by_lvalue_reference;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&&)
|
|
{
|
|
return passed_by_rvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&&)
|
|
{
|
|
return passed_by_rvalue_reference;
|
|
}
|
|
};
|
|
</pre>
|
|
<p>Define the named parameters that will comprise the argument specification that
|
|
this macro will use. Ensure that all their tag types are in the same
|
|
namespace, which is <tt class="docutils literal">kw</tt> in this case. The identifiers with leading
|
|
underscores can be passed to the bracket operator of <tt class="docutils literal">args</tt> to extract the
|
|
same argument to which the corresponding named parameter (without underscores)
|
|
is bound, as will be shown later.</p>
|
|
<pre class="literal-block">
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lrc, kw) in(lrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lr, kw) in_out(lr))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rrc, kw) in(rrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rr, kw) consume(rr))
|
|
</pre>
|
|
<p>Use the macro as a substitute for a normal <tt class="docutils literal">static</tt> member function
|
|
header. Enclose the return type <tt class="docutils literal">bool</tt> in parentheses. For each parameter,
|
|
also enclose the expected value type in parentheses. Since the value types
|
|
are mutually exclusive, you can wrap the parameters in a <tt class="docutils literal">(deduced …)</tt>
|
|
clause. Otherwise, just as with a normal function, the order in which you
|
|
specify the parameters determines their position. Also, just as with a normal
|
|
function, optional parameters have default values, whereas required parameters
|
|
do not. Within the function body, either simply use the parameter name or
|
|
pass the matching identifier with the leading underscore to the bracket
|
|
operator of <tt class="docutils literal">args</tt> to extract the corresponding argument. Note that the
|
|
second method doesn't require <tt class="docutils literal"><span class="pre">std::forward</span></tt> to preserve value categories.</p>
|
|
<pre class="literal-block">
|
|
struct B
|
|
{
|
|
BOOST_PARAMETER_MEMBER_FUNCTION((bool), static evaluate, kw,
|
|
(deduced
|
|
(required
|
|
(lrc, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><1>))
|
|
(lr, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><2>))
|
|
)
|
|
(optional
|
|
(rrc, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><3>), rvalue_const_bitset<2>())
|
|
(rr, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><4>), rvalue_bitset<3>())
|
|
)
|
|
)
|
|
)
|
|
{
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference_to_const
|
|
, U::evaluate_category<0>(lrc)
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference
|
|
, U::evaluate_category<1>(lr)
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference_to_const
|
|
, U::evaluate_category<2>(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><rrc0_type>(rrc0))
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference
|
|
, U::evaluate_category<3>(args[_rr0])
|
|
);
|
|
|
|
return true;
|
|
}
|
|
};
|
|
</pre>
|
|
<p>The following function calls are legal.</p>
|
|
<pre class="literal-block">
|
|
B::evaluate( // positional arguments
|
|
lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
, rvalue_const_bitset<2>()
|
|
, rvalue_bitset<3>()
|
|
);
|
|
B::evaluate( // positional arguments
|
|
lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
);
|
|
B::evaluate(( // composed arguments
|
|
_rr0 = rvalue_bitset<3>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
, _lr0 = lvalue_bitset<1>()
|
|
, _rrc0 = rvalue_const_bitset<2>()
|
|
));
|
|
B::evaluate( // named arguments
|
|
_rr0 = rvalue_bitset<3>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
, _lr0 = lvalue_bitset<1>()
|
|
, _rrc0 = rvalue_const_bitset<2>()
|
|
);
|
|
B::evaluate( // named arguments
|
|
_lr0 = lvalue_bitset<1>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
);
|
|
</pre>
|
|
<p>Because the parameters were wrapped in a <tt class="docutils literal">(deduced …)</tt> clause, the following
|
|
function calls are also legal.</p>
|
|
<pre class="literal-block">
|
|
B::evaluate( // deduced arguments
|
|
rvalue_bitset<3>()
|
|
, lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
, rvalue_const_bitset<2>()
|
|
);
|
|
B::evaluate( // deduced arguments
|
|
lvalue_bitset<1>()
|
|
, lvalue_const_bitset<0>()
|
|
);
|
|
</pre>
|
|
<p>The <a class="reference external" href="../../test/preprocessor.cpp">preprocessor.cpp</a> and <a class="reference external" href="../../test/preprocessor_eval_category.cpp">preprocessor_eval_category.cpp</a> test programs
|
|
demonstrate proper usage of this macro.</p>
|
|
<p><strong>Macro parameters:</strong></p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">result</tt> is the parenthesized return type of the function.</li>
|
|
<li><tt class="docutils literal">name</tt> is the base name of the function; it determines the name of the
|
|
generated forwarding functions. <tt class="docutils literal">name</tt> may be qualified by the
|
|
<tt class="docutils literal">static</tt> keyword to declare the member function and its helpers as not
|
|
associated with any object of the enclosing type.</li>
|
|
<li><tt class="docutils literal">tag_namespace</tt> is the namespace in which the keywords used by the
|
|
function resides.</li>
|
|
<li><tt class="docutils literal">arguments</tt> is a <a class="reference external" href="../../../preprocessor/doc/index.html">Boost.Preprocessor</a> <a class="reference external" href="../../../preprocessor/doc/data/sequences.html">sequence</a> of
|
|
<em>argument-specifiers</em>, as defined below.</li>
|
|
</ul>
|
|
<p><strong>Argument specifiers syntax:</strong></p>
|
|
<pre class="literal-block">
|
|
argument-specifiers ::= <em>specifier-group0</em> {<em>specifier-group0</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>argument-name</em> '<strong>,</strong>' <em>restriction</em> '<strong>,</strong>' <em>default-value</em>
|
|
')'
|
|
|
|
required-specifier ::=
|
|
'<strong>(</strong>' <em>argument-name</em> '<strong>,</strong>' <em>restriction</em> ')'
|
|
|
|
restriction ::=
|
|
( '<strong>*</strong>' '<strong>(</strong>' <em>mfc</em> '<strong>)</strong>' ) |
|
|
( '<strong>(</strong>' <em>type-name</em> '<strong>)</strong>' ) |
|
|
'<strong>*</strong>'
|
|
</pre>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal"><span class="pre">argument-name</span></tt> is any valid C++ identifier.</li>
|
|
<li><tt class="docutils literal"><span class="pre">default-value</span></tt> is any valid C++ expression; if necessary, user code can
|
|
compute it in terms of <tt class="docutils literal"><span class="pre">previous-name</span> ## _type</tt>, where <tt class="docutils literal"><span class="pre">previous-name</span></tt>
|
|
is the <tt class="docutils literal"><span class="pre">argument-name</span></tt> in a previous <tt class="docutils literal"><span class="pre">specifier-group0</span></tt> or
|
|
<tt class="docutils literal"><span class="pre">specifier-group1</span></tt>. <em>This expression will be invoked exactly once.</em></li>
|
|
<li><tt class="docutils literal">mfc</tt> is an <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary Metafunction Class</a> whose first argument will
|
|
be the type of the corresponding <tt class="docutils literal"><span class="pre">argument-name</span></tt>, whose second argument
|
|
will be the entire <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>, and whose return type is a <a class="reference external" href="../../../mpl/doc/refmanual/integral-constant.html">Boolean
|
|
Integral Constant</a>; however, user code <em>cannot</em> compute <tt class="docutils literal">mfc</tt> in terms
|
|
of <tt class="docutils literal"><span class="pre">previous-name</span> ## _type</tt>.</li>
|
|
<li><tt class="docutils literal"><span class="pre">type-name</span></tt> is either the name of a <strong>target type</strong> or an <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary
|
|
Metafunction Class</a> whose first argument will be the type of the
|
|
corresponding <tt class="docutils literal"><span class="pre">argument-name</span></tt>, whose second argument will be the entire
|
|
<a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>, and whose return type is the <strong>target type</strong>. If
|
|
<tt class="docutils literal">restriction</tt> uses this form, then the type of the generated name
|
|
<tt class="docutils literal"><span class="pre">argument-name</span> ## _type</tt> will be computed in terms of the <strong>target
|
|
type</strong>, and the generated reference <tt class="docutils literal"><span class="pre">argument-name</span></tt> (but not its
|
|
corresponding entry in <tt class="docutils literal">args</tt>) will be cast to that type.</li>
|
|
</ul>
|
|
<p><strong>Approximate expansion:</strong></p>
|
|
<p>Where:</p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">n</tt> denotes the <em>minimum</em> arity, as determined from <tt class="docutils literal">arguments</tt>.</li>
|
|
<li><tt class="docutils literal">m</tt> denotes the <em>maximum</em> arity, as determined from <tt class="docutils literal">arguments</tt>.</li>
|
|
</ul>
|
|
<pre class="literal-block">
|
|
// If <strong>result</strong> is a template instantiation of <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if_c</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if_c</a>, or
|
|
// <a class="reference external" href="http://en.cppreference.com/w/cpp/types/enable_if">std::enable_if</a>:
|
|
template <typename Args>
|
|
using boost_param_result_ ## __LINE__ ## <strong>name</strong> = <strong>result</strong>;
|
|
|
|
// If <strong>result</strong> is a simple return type:
|
|
template <typename Args>
|
|
struct boost_param_result_ ## __LINE__ ## <strong>name</strong>
|
|
{
|
|
typedef <strong>result</strong> type;
|
|
};
|
|
|
|
struct boost_param_params_ ## __LINE__ ## <strong>name</strong>
|
|
: <a class="reference internal" href="#parameters"><tt class="docutils literal">parameters</tt></a><
|
|
<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 <typename A0, …, typename A ## <strong>n</strong>>
|
|
<strong>result</strong> <strong>name</strong>(
|
|
A0&& a0, …, A ## <strong>n</strong>&& a ## <strong>n</strong>
|
|
, typename boost_param_parameters_ ## __LINE__ ## <strong>name</strong>
|
|
::match<A0, …, A ## <strong>n</strong>>::type
|
|
= boost_param_parameters_ ## __LINE__ ## <strong>name</strong>()
|
|
)
|
|
{
|
|
return this->boost_param_impl ## __LINE__ ## <strong>name</strong>(
|
|
boost_param_parameters_ ## __LINE__ ## <strong>name</strong>()(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A0>(a0)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>n</strong>>(a ## <strong>n</strong>)
|
|
)
|
|
);
|
|
}
|
|
|
|
<span class="vellipsis">⋮</span>
|
|
|
|
template <typename A0, …, typename A ## <strong>m</strong>>
|
|
<strong>result</strong> <strong>name</strong>(
|
|
A0&& a0, …, A ## <strong>m</strong>&& a ## <strong>m</strong>
|
|
, typename boost_param_parameters_ ## __LINE__ ## <strong>name</strong>
|
|
::match<A0, …, A ## <strong>m</strong>>::type
|
|
= boost_param_parameters_ ## __LINE__ ## <strong>name</strong>()
|
|
)
|
|
{
|
|
return this->boost_param_impl ## __LINE__ ## <strong>name</strong>(
|
|
boost_param_parameters_ ## __LINE__ ## <strong>name</strong>()(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A0>(a0)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>m</strong>>(a ## <strong>m</strong>)
|
|
)
|
|
);
|
|
}
|
|
|
|
template <typename Args>
|
|
typename boost_param_result_ ## __LINE__ ## <strong>name</strong><Args>::type
|
|
boost_param_impl ## __LINE__ ## <strong>name</strong>(Args const& args)
|
|
{
|
|
return this->boost_param_dispatch_0boost_ ## __LINE__ ## <strong>name</strong>(
|
|
static_cast<
|
|
typename boost_param_result_ ## __LINE__ ## <strong>name</strong><
|
|
Args
|
|
>::type(*)()
|
|
>(<a class="reference external" href="http://en.cppreference.com/w/cpp/language/nullptr">std::nullptr</a>)
|
|
, args
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><
|
|
typename <a class="reference internal" href="#value-type"><tt class="docutils literal">value_type</tt></a><
|
|
Args
|
|
, <em>keyword tag type of required parameter</em> ## <strong>0</strong>
|
|
>::type
|
|
>(args[ <em>keyword object of required parameter</em> ## <strong>0</strong>])
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><
|
|
typename <a class="reference internal" href="#value-type"><tt class="docutils literal">value_type</tt></a><
|
|
Args
|
|
, <em>keyword tag type of required parameter</em> ## <strong>n</strong>
|
|
>::type
|
|
>(args[ <em>keyword object of required parameter</em> ## <strong>n</strong>])
|
|
);
|
|
}
|
|
|
|
template <
|
|
typename ResultType
|
|
, typename Args
|
|
, typename <em>argument name</em> ## <strong>0</strong> ## _type
|
|
, …
|
|
, typename <em>argument name</em> ## <strong>n</strong> ## _type
|
|
>
|
|
ResultType
|
|
boost_param_dispatch_0boost_ ## __LINE__ ## <strong>name</strong>(
|
|
(ResultType(*)())
|
|
, Args const& args
|
|
, <em>argument name</em> ## <strong>0</strong> ## _type&& <em>argument name</em> ## <strong>0</strong>
|
|
, …
|
|
, <em>argument name</em> ## <strong>n</strong> ## _type&& <em>argument name</em> ## <strong>n</strong>
|
|
)
|
|
{
|
|
return this->boost_param_dispatch_0boost_ ## __LINE__ ## <strong>name</strong>(
|
|
static_cast<ResultType(*)()>(<a class="reference external" href="http://en.cppreference.com/w/cpp/language/nullptr">std::nullptr</a>)
|
|
, (args, <em>keyword object of optional parameter</em> ## <strong>n + 1</strong> =
|
|
<em>default value of optional parameter</em> ## <strong>n + 1</strong>
|
|
)
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><<em>argument name</em> ## <strong>0</strong> ## _type>(
|
|
<em>argument name</em> ## <strong>0</strong>
|
|
)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><<em>argument name</em> ## <strong>n</strong> ## _type>(
|
|
<em>argument name</em> ## <strong>n</strong>
|
|
)
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><
|
|
typename <a class="reference internal" href="#value-type"><tt class="docutils literal">value_type</tt></a><
|
|
Args
|
|
, <em>keyword tag type of optional parameter</em> ## <strong>n + 1</strong>
|
|
>::type
|
|
>(<em>default value of optional parameter</em> ## <strong>n + 1</strong>)
|
|
);
|
|
}
|
|
|
|
<span class="vellipsis">⋮</span>
|
|
|
|
template <
|
|
typename ResultType
|
|
, typename Args
|
|
, typename <em>argument name</em> ## <strong>0</strong> ## _type
|
|
, …
|
|
, typename <em>argument name</em> ## <strong>m</strong> ## _type
|
|
>
|
|
ResultType
|
|
boost_param_dispatch_0boost_ ## __LINE__ ## <strong>name</strong>(
|
|
(ResultType(*)())
|
|
, Args const& args
|
|
, <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>
|
|
</div>
|
|
<div class="section" id="boost-parameter-const-member-function-result-name-tag-ns-arguments">
|
|
<span id="boost-parameter-const-member-function"></span><h2><a class="toc-backref" href="#id59">7.3 <tt class="docutils literal">BOOST_PARAMETER_CONST_MEMBER_FUNCTION(result, name, tag_ns, arguments)</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>
|
|
<p>Generates a member function that can take in positional arguments, composed
|
|
arguments, named arguments, and deduced 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">Example usage:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>The return type of each of the following function templates falls under a
|
|
different value category.</p>
|
|
<pre class="literal-block">
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> rvalue_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const rvalue_const_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>& lvalue_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> lset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return lset;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const& lvalue_const_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const clset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return clset;
|
|
}
|
|
</pre>
|
|
<p>The <tt class="docutils literal"><span class="pre">U::evaluate_category</span></tt> static member function template has a simple job:
|
|
to return the correct value category when passed in an object returned by one
|
|
of the functions defined above. Assume that
|
|
<a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> is defined.</p>
|
|
<pre class="literal-block">
|
|
enum invoked
|
|
{
|
|
passed_by_lvalue_reference_to_const
|
|
, passed_by_lvalue_reference
|
|
, passed_by_rvalue_reference_to_const
|
|
, passed_by_rvalue_reference
|
|
};
|
|
|
|
struct U
|
|
{
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&)
|
|
{
|
|
return passed_by_lvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&)
|
|
{
|
|
return passed_by_lvalue_reference;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&&)
|
|
{
|
|
return passed_by_rvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&&)
|
|
{
|
|
return passed_by_rvalue_reference;
|
|
}
|
|
};
|
|
</pre>
|
|
<p>Define the named parameters that will comprise the argument specification that
|
|
this macro will use. Ensure that all their tag types are in the same
|
|
namespace, which is <tt class="docutils literal">kw</tt> in this case. The identifiers with leading
|
|
underscores can be passed to the bracket operator of <tt class="docutils literal">args</tt> to extract the
|
|
same argument to which the corresponding named parameter (without underscores)
|
|
is bound, as will be shown later.</p>
|
|
<pre class="literal-block">
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lrc, kw) in(lrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lr, kw) in_out(lr))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rrc, kw) in(rrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rr, kw) consume(rr))
|
|
</pre>
|
|
<p>Use the macro as a substitute for a normal <tt class="docutils literal">const</tt> member function
|
|
header. Enclose the return type <tt class="docutils literal">bool</tt> in parentheses. For each parameter,
|
|
also enclose the expected value type in parentheses. Since the value types
|
|
are mutually exclusive, you can wrap the parameters in a <tt class="docutils literal">(deduced …)</tt>
|
|
clause. Otherwise, just as with a normal function, the order in which you
|
|
specify the parameters determines their position. Also, just as with a normal
|
|
function, optional parameters have default values, whereas required parameters
|
|
do not. Within the function body, either simply use the parameter name or
|
|
pass the matching identifier with the leading underscore to the bracket
|
|
operator of <tt class="docutils literal">args</tt> to extract the corresponding argument. Note that the
|
|
second method doesn't require <tt class="docutils literal"><span class="pre">std::forward</span></tt> to preserve value categories.</p>
|
|
<pre class="literal-block">
|
|
struct B
|
|
{
|
|
B()
|
|
{
|
|
}
|
|
|
|
BOOST_PARAMETER_CONST_MEMBER_FUNCTION((bool), evaluate, kw,
|
|
(deduced
|
|
(required
|
|
(lrc, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><1>))
|
|
(lr, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><2>))
|
|
)
|
|
(optional
|
|
(rrc, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><3>), rvalue_const_bitset<2>())
|
|
(rr, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><4>), rvalue_bitset<3>())
|
|
)
|
|
)
|
|
)
|
|
{
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference_to_const
|
|
, U::evaluate_category<0>(lrc)
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference
|
|
, U::evaluate_category<1>(lr)
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference_to_const
|
|
, U::evaluate_category<2>(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><rrc0_type>(rrc0))
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference
|
|
, U::evaluate_category<3>(args[_rr0])
|
|
);
|
|
|
|
return true;
|
|
}
|
|
};
|
|
</pre>
|
|
<p>The following function calls are legal.</p>
|
|
<pre class="literal-block">
|
|
B const b = B();
|
|
b.evaluate( // positional arguments
|
|
lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
, rvalue_const_bitset<2>()
|
|
, rvalue_bitset<3>()
|
|
);
|
|
b.evaluate( // positional arguments
|
|
lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
);
|
|
b.evaluate(( // composed arguments
|
|
_rr0 = rvalue_bitset<3>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
, _lr0 = lvalue_bitset<1>()
|
|
, _rrc0 = rvalue_const_bitset<2>()
|
|
));
|
|
b.evaluate( // named arguments
|
|
_rr0 = rvalue_bitset<3>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
, _lr0 = lvalue_bitset<1>()
|
|
, _rrc0 = rvalue_const_bitset<2>()
|
|
);
|
|
b.evaluate( // named arguments
|
|
_lr0 = lvalue_bitset<1>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
);
|
|
</pre>
|
|
<p>Because the parameters were wrapped in a <tt class="docutils literal">(deduced …)</tt> clause, the following
|
|
function calls are also legal.</p>
|
|
<pre class="literal-block">
|
|
b.evaluate( // deduced arguments
|
|
rvalue_bitset<3>()
|
|
, lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
, rvalue_const_bitset<2>()
|
|
);
|
|
b.evaluate( // deduced arguments
|
|
lvalue_bitset<1>()
|
|
, lvalue_const_bitset<0>()
|
|
);
|
|
</pre>
|
|
<p>The <a class="reference external" href="../../test/preprocessor.cpp">preprocessor.cpp</a> test program demonstrates proper usage of this macro.</p>
|
|
<p><strong>Macro parameters:</strong></p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">result</tt> is the parenthesized return type of the function.</li>
|
|
<li><tt class="docutils literal">name</tt> is the base name of the function; it determines the name of the
|
|
generated forwarding functions.</li>
|
|
<li><tt class="docutils literal">tag_namespace</tt> is the namespace in which the keywords used by the
|
|
function resides.</li>
|
|
<li><tt class="docutils literal">arguments</tt> is a <a class="reference external" href="../../../preprocessor/doc/index.html">Boost.Preprocessor</a> <a class="reference external" href="../../../preprocessor/doc/data/sequences.html">sequence</a> of
|
|
<em>argument-specifiers</em>, as defined below.</li>
|
|
</ul>
|
|
<p><strong>Argument specifiers syntax:</strong></p>
|
|
<pre class="literal-block">
|
|
argument-specifiers ::= <em>specifier-group0</em> {<em>specifier-group0</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>argument-name</em> '<strong>,</strong>' <em>restriction</em> '<strong>,</strong>' <em>default-value</em>
|
|
')'
|
|
|
|
required-specifier ::=
|
|
'<strong>(</strong>' <em>argument-name</em> '<strong>,</strong>' <em>restriction</em> ')'
|
|
|
|
restriction ::=
|
|
( '<strong>*</strong>' '<strong>(</strong>' <em>mfc</em> '<strong>)</strong>' ) |
|
|
( '<strong>(</strong>' <em>type-name</em> '<strong>)</strong>' ) |
|
|
'<strong>*</strong>'
|
|
</pre>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal"><span class="pre">argument-name</span></tt> is any valid C++ identifier.</li>
|
|
<li><tt class="docutils literal"><span class="pre">default-value</span></tt> is any valid C++ expression; if necessary, user code can
|
|
compute it in terms of <tt class="docutils literal"><span class="pre">previous-name</span> ## _type</tt>, where <tt class="docutils literal"><span class="pre">previous-name</span></tt>
|
|
is the <tt class="docutils literal"><span class="pre">argument-name</span></tt> in a previous <tt class="docutils literal"><span class="pre">specifier-group0</span></tt> or
|
|
<tt class="docutils literal"><span class="pre">specifier-group1</span></tt>. <em>This expression will be invoked exactly once.</em></li>
|
|
<li><tt class="docutils literal">mfc</tt> is an <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary Metafunction Class</a> whose first argument will
|
|
be the type of the corresponding <tt class="docutils literal"><span class="pre">argument-name</span></tt>, whose second argument
|
|
will be the entire <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>, and whose return type is a <a class="reference external" href="../../../mpl/doc/refmanual/integral-constant.html">Boolean
|
|
Integral Constant</a>; however, user code <em>cannot</em> compute <tt class="docutils literal">mfc</tt> in terms
|
|
of <tt class="docutils literal"><span class="pre">previous-name</span> ## _type</tt>.</li>
|
|
<li><tt class="docutils literal"><span class="pre">type-name</span></tt> is either the name of a <strong>target type</strong> or an <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary
|
|
Metafunction Class</a> whose first argument will be the type of the
|
|
corresponding <tt class="docutils literal"><span class="pre">argument-name</span></tt>, whose second argument will be the entire
|
|
<a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>, and whose return type is the <strong>target type</strong>. If
|
|
<tt class="docutils literal">restriction</tt> uses this form, then the type of the generated name
|
|
<tt class="docutils literal"><span class="pre">argument-name</span> ## _type</tt> will be computed in terms of the <strong>target
|
|
type</strong>, and the generated reference <tt class="docutils literal"><span class="pre">argument-name</span></tt> (but not its
|
|
corresponding entry in <tt class="docutils literal">args</tt>) will be cast to that type.</li>
|
|
</ul>
|
|
<p><strong>Approximate expansion:</strong></p>
|
|
<p>Where:</p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">n</tt> denotes the <em>minimum</em> arity, as determined from <tt class="docutils literal">arguments</tt>.</li>
|
|
<li><tt class="docutils literal">m</tt> denotes the <em>maximum</em> arity, as determined from <tt class="docutils literal">arguments</tt>.</li>
|
|
</ul>
|
|
<pre class="literal-block">
|
|
// If <strong>result</strong> is a template instantiation of <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if_c</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if_c</a>, or
|
|
// <a class="reference external" href="http://en.cppreference.com/w/cpp/types/enable_if">std::enable_if</a>:
|
|
template <typename Args>
|
|
using boost_param_result_const_ ## __LINE__ ## <strong>name</strong> = <strong>result</strong>;
|
|
|
|
// If <strong>result</strong> is a simple return type:
|
|
template <typename Args>
|
|
struct boost_param_result_const_ ## __LINE__ ## <strong>name</strong>
|
|
{
|
|
typedef <strong>result</strong> type;
|
|
};
|
|
|
|
struct boost_param_params_const_ ## __LINE__ ## <strong>name</strong>
|
|
: <a class="reference internal" href="#parameters"><tt class="docutils literal">parameters</tt></a><
|
|
<em>list of parameter specifications, based on arguments</em>
|
|
>
|
|
{
|
|
};
|
|
|
|
typedef boost_param_params_const_ ## __LINE__ ## <strong>name</strong>
|
|
boost_param_parameters_const_ ## __LINE__ ## <strong>name</strong>;
|
|
|
|
template <typename A0, …, typename A ## <strong>n</strong>>
|
|
<strong>result</strong> <strong>name</strong>(
|
|
A0&& a0, …, A ## <strong>n</strong>&& a ## <strong>n</strong>
|
|
, typename boost_param_parameters_const_ ## __LINE__ ## <strong>name</strong>
|
|
::match<A0, …, A ## <strong>n</strong>>::type
|
|
= boost_param_parameters_const_ ## __LINE__ ## <strong>name</strong>()
|
|
) const
|
|
{
|
|
return this->boost_param_impl_const ## __LINE__ ## <strong>name</strong>(
|
|
boost_param_parameters_const_ ## __LINE__ ## <strong>name</strong>(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A0>(a0)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>n</strong>>(a ## <strong>n</strong>)
|
|
)
|
|
);
|
|
}
|
|
|
|
<span class="vellipsis">⋮</span>
|
|
|
|
template <typename A0, …, typename A ## <strong>m</strong>>
|
|
<strong>result</strong> <strong>name</strong>(
|
|
A0&& a0, …, A ## <strong>m</strong>&& a ## <strong>m</strong>
|
|
, typename boost_param_parameters_const_ ## __LINE__ ## <strong>name</strong>
|
|
::match<A0, …, A ## <strong>m</strong>>::type
|
|
= boost_param_parameters_const_ ## __LINE__ ## <strong>name</strong>()
|
|
) const
|
|
{
|
|
return this->boost_param_impl_const ## __LINE__ ## <strong>name</strong>(
|
|
boost_param_parameters_const_ ## __LINE__ ## <strong>name</strong>()(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A0>(a0)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>m</strong>>(a ## <strong>m</strong>)
|
|
)
|
|
);
|
|
}
|
|
|
|
template <typename Args>
|
|
typename boost_param_result_const_ ## __LINE__ ## <strong>name</strong><Args>::type
|
|
boost_param_impl_const ## __LINE__ ## <strong>name</strong>(Args const& args) const
|
|
{
|
|
return this->
|
|
boost_param_dispatch_const_0boost_ ## __LINE__ ## <strong>name</strong>(
|
|
static_cast<
|
|
typename boost_param_result_const_ ## __LINE__ ## <strong>name</strong><
|
|
Args
|
|
>::type(*)()
|
|
>(<a class="reference external" href="http://en.cppreference.com/w/cpp/language/nullptr">std::nullptr</a>)
|
|
, args
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><
|
|
typename <a class="reference internal" href="#value-type"><tt class="docutils literal">value_type</tt></a><
|
|
Args
|
|
, <em>keyword tag type of required parameter</em> ## <strong>0</strong>
|
|
>::type
|
|
>(args[ <em>keyword object of required parameter</em> ## <strong>0</strong>])
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><
|
|
typename <a class="reference internal" href="#value-type"><tt class="docutils literal">value_type</tt></a><
|
|
Args
|
|
, <em>keyword tag type of required parameter</em> ## <strong>n</strong>
|
|
>::type
|
|
>(args[ <em>keyword object of required parameter</em> ## <strong>n</strong>])
|
|
);
|
|
}
|
|
|
|
template <
|
|
typename ResultType
|
|
, typename Args
|
|
, typename <em>argument name</em> ## <strong>0</strong> ## _type
|
|
, …
|
|
, typename <em>argument name</em> ## <strong>n</strong> ## _type
|
|
>
|
|
ResultType
|
|
boost_param_dispatch_const_0boost_ ## __LINE__ ## <strong>name</strong>(
|
|
(ResultType(*)())
|
|
, Args const& args
|
|
, <em>argument name</em> ## <strong>0</strong> ## _type&& <em>argument name</em> ## <strong>0</strong>
|
|
, …
|
|
, <em>argument name</em> ## <strong>n</strong> ## _type&& <em>argument name</em> ## <strong>n</strong>
|
|
) const
|
|
{
|
|
return this->
|
|
boost_param_dispatch_const_0boost_ ## __LINE__ ## <strong>name</strong>(
|
|
static_cast<ResultType(*)()>(<a class="reference external" href="http://en.cppreference.com/w/cpp/language/nullptr">std::nullptr</a>)
|
|
, (args, <em>keyword object of optional parameter</em> ## <strong>n + 1</strong> =
|
|
<em>default value of optional parameter</em> ## <strong>n + 1</strong>
|
|
)
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><<em>argument name</em> ## <strong>0</strong> ## _type>(
|
|
<em>argument name</em> ## <strong>0</strong>
|
|
)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><<em>argument name</em> ## <strong>n</strong> ## _type>(
|
|
<em>argument name</em> ## <strong>n</strong>
|
|
)
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><
|
|
typename <a class="reference internal" href="#value-type"><tt class="docutils literal">value_type</tt></a><
|
|
Args
|
|
, <em>keyword tag type of optional parameter</em> ## <strong>n + 1</strong>
|
|
>::type
|
|
>(<em>default value of optional parameter</em> ## <strong>n + 1</strong>)
|
|
);
|
|
}
|
|
|
|
<span class="vellipsis">⋮</span>
|
|
|
|
template <
|
|
typename ResultType
|
|
, typename Args
|
|
, typename <em>argument name</em> ## <strong>0</strong> ## _type
|
|
, …
|
|
, typename <em>argument name</em> ## <strong>m</strong> ## _type
|
|
>
|
|
ResultType
|
|
boost_param_dispatch_const_0boost_ ## __LINE__ ## <strong>name</strong>(
|
|
(ResultType(*)())
|
|
, Args const& args
|
|
, <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>
|
|
) const
|
|
</pre>
|
|
</div>
|
|
<div class="section" id="boost-parameter-function-call-operator-result-tag-namespace-arguments">
|
|
<span id="boost-parameter-function-call-operator"></span><h2><a class="toc-backref" href="#id60">7.4 <tt class="docutils literal">BOOST_PARAMETER_FUNCTION_CALL_OPERATOR(result, tag_namespace, arguments)</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>
|
|
<p>Generates a function call operator that can take in positional arguments,
|
|
composed arguments, named arguments, and deduced 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">Example usage:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>Define the named parameters that will comprise the argument specification that
|
|
this macro will use. Ensure that all their tag types are in the same
|
|
namespace, which is <tt class="docutils literal">tag</tt> by default.</p>
|
|
<pre class="literal-block">
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>(y)
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>(z)
|
|
</pre>
|
|
<p>Use the macro as a substitute for a normal function call operator
|
|
header. Enclose the return type in parentheses. For each parameter, also
|
|
enclose the expected value type in parentheses. Since the value types are
|
|
mutually exclusive, you can wrap the parameters in a <tt class="docutils literal">(deduced …)</tt>
|
|
clause. This is especially useful when implementing multiple
|
|
Boost.Parameter-enabled function call operator overloads.</p>
|
|
<pre class="literal-block">
|
|
class char_reader
|
|
{
|
|
int index;
|
|
char const* key;
|
|
|
|
public:
|
|
explicit char_reader(char const* k) : index(0), key(k)
|
|
{
|
|
}
|
|
|
|
BOOST_PARAMETER_FUNCTION_CALL_OPERATOR((void), tag,
|
|
(deduced
|
|
(required
|
|
(y, (int))
|
|
(z, (char const*))
|
|
)
|
|
)
|
|
)
|
|
{
|
|
this->index = y;
|
|
this->key = z;
|
|
}
|
|
|
|
<a class="reference internal" href="#boost-parameter-const-function-call-operator"><tt class="docutils literal">BOOST_PARAMETER_CONST_FUNCTION_CALL_OPERATOR</tt></a>((char), tag,
|
|
(deduced
|
|
(required
|
|
(y, (bool))
|
|
(z, (<a class="reference external" href="http://en.cppreference.com/w/cpp/container/map">std::map</a><char const*, <a class="reference external" href="http://en.cppreference.com/w/cpp/string/basic_string">std::string</a>>))
|
|
)
|
|
)
|
|
)
|
|
{
|
|
return y ? (
|
|
(z.find(this->key)->second)[this->index]
|
|
) : this->key[this->index];
|
|
}
|
|
};
|
|
</pre>
|
|
<p>As with regular argument-dependent lookup, the value types of the arguments
|
|
passed in determine which function call operator overload gets invoked.</p>
|
|
<pre class="literal-block">
|
|
char const* keys[] = {"foo", "bar", "baz"};
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/container/map">std::map</a><char const*, <a class="reference external" href="http://en.cppreference.com/w/cpp/string/basic_string">std::string</a>> k2s;
|
|
k2s[keys[0]] = <a class="reference external" href="http://en.cppreference.com/w/cpp/string/basic_string">std::string</a>("qux");
|
|
k2s[keys[1]] = <a class="reference external" href="http://en.cppreference.com/w/cpp/string/basic_string">std::string</a>("wmb");
|
|
k2s[keys[2]] = <a class="reference external" href="http://en.cppreference.com/w/cpp/string/basic_string">std::string</a>("zxc");
|
|
char_reader r(keys[0]);
|
|
|
|
// positional arguments
|
|
BOOST_TEST_EQ('q', (r(true, k2s)));
|
|
BOOST_TEST_EQ('f', (r(false, k2s)));
|
|
|
|
// named arguments
|
|
r(_z = keys[1], _y = 1);
|
|
BOOST_TEST_EQ('m', (r(_z = k2s, _y = true)));
|
|
BOOST_TEST_EQ('a', (r(_z = k2s, _y = false)));
|
|
|
|
// deduced arguments
|
|
r(keys[2], 2);
|
|
BOOST_TEST_EQ('c', (r(k2s, true)));
|
|
BOOST_TEST_EQ('z', (r(k2s, false)));
|
|
</pre>
|
|
<p>The <a class="reference external" href="../../test/preprocessor.cpp">preprocessor.cpp</a> and <a class="reference external" href="../../test/preprocessor_deduced.cpp">preprocessor_deduced.cpp</a> test programs
|
|
demonstrate proper usage of this macro.</p>
|
|
<p><strong>Macro parameters:</strong></p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">result</tt> is the parenthesized return type of the function call operator.</li>
|
|
<li><tt class="docutils literal">tag_namespace</tt> is the namespace in which the keywords used by the
|
|
function call operator resides.</li>
|
|
<li><tt class="docutils literal">arguments</tt> is a <a class="reference external" href="../../../preprocessor/doc/index.html">Boost.Preprocessor</a> <a class="reference external" href="../../../preprocessor/doc/data/sequences.html">sequence</a> of
|
|
<em>argument-specifiers</em>, as defined below.</li>
|
|
</ul>
|
|
<p><strong>Argument specifiers syntax:</strong></p>
|
|
<pre class="literal-block">
|
|
argument-specifiers ::= <em>specifier-group0</em> {<em>specifier-group0</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>argument-name</em> '<strong>,</strong>' <em>restriction</em> '<strong>,</strong>' <em>default-value</em>
|
|
')'
|
|
|
|
required-specifier ::=
|
|
'<strong>(</strong>' <em>argument-name</em> '<strong>,</strong>' <em>restriction</em> ')'
|
|
|
|
restriction ::=
|
|
( '<strong>*</strong>' '<strong>(</strong>' <em>mfc</em> '<strong>)</strong>' ) |
|
|
( '<strong>(</strong>' <em>type-name</em> '<strong>)</strong>' ) |
|
|
'<strong>*</strong>'
|
|
</pre>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal"><span class="pre">argument-name</span></tt> is any valid C++ identifier.</li>
|
|
<li><tt class="docutils literal"><span class="pre">default-value</span></tt> is any valid C++ expression; if necessary, user code can
|
|
compute it in terms of <tt class="docutils literal"><span class="pre">previous-name</span> ## _type</tt>, where <tt class="docutils literal"><span class="pre">previous-name</span></tt>
|
|
is the <tt class="docutils literal"><span class="pre">argument-name</span></tt> in a previous <tt class="docutils literal"><span class="pre">specifier-group0</span></tt> or
|
|
<tt class="docutils literal"><span class="pre">specifier-group1</span></tt>. <em>This expression will be invoked exactly once.</em></li>
|
|
<li><tt class="docutils literal">mfc</tt> is an <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary Metafunction Class</a> whose first argument will
|
|
be the type of the corresponding <tt class="docutils literal"><span class="pre">argument-name</span></tt>, whose second argument
|
|
will be the entire <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>, and whose return type is a <a class="reference external" href="../../../mpl/doc/refmanual/integral-constant.html">Boolean
|
|
Integral Constant</a>; however, user code <em>cannot</em> compute <tt class="docutils literal">mfc</tt> in terms
|
|
of <tt class="docutils literal"><span class="pre">previous-name</span> ## _type</tt>.</li>
|
|
<li><tt class="docutils literal"><span class="pre">type-name</span></tt> is either the name of a <strong>target type</strong> or an <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary
|
|
Metafunction Class</a> whose first argument will be the type of the
|
|
corresponding <tt class="docutils literal"><span class="pre">argument-name</span></tt>, whose second argument will be the entire
|
|
<a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>, and whose return type is the <strong>target type</strong>. If
|
|
<tt class="docutils literal">restriction</tt> uses this form, then the type of the generated name
|
|
<tt class="docutils literal"><span class="pre">argument-name</span> ## _type</tt> will be computed in terms of the <strong>target
|
|
type</strong>, and the generated reference <tt class="docutils literal"><span class="pre">argument-name</span></tt> (but not its
|
|
corresponding entry in <tt class="docutils literal">args</tt>) will be cast to that type.</li>
|
|
</ul>
|
|
<p><strong>Approximate expansion:</strong></p>
|
|
<p>Where:</p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">n</tt> denotes the <em>minimum</em> arity, as determined from <tt class="docutils literal">arguments</tt>.</li>
|
|
<li><tt class="docutils literal">m</tt> denotes the <em>maximum</em> arity, as determined from <tt class="docutils literal">arguments</tt>.</li>
|
|
</ul>
|
|
<pre class="literal-block">
|
|
// If <strong>result</strong> is a template instantiation of <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if_c</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if_c</a>, or
|
|
// <a class="reference external" href="http://en.cppreference.com/w/cpp/types/enable_if">std::enable_if</a>:
|
|
template <typename Args>
|
|
using boost_param_result_ ## __LINE__ ## operator = <strong>result</strong>;
|
|
|
|
// If <strong>result</strong> is a simple return type:
|
|
template <typename Args>
|
|
struct boost_param_result_ ## __LINE__ ## operator
|
|
{
|
|
typedef <strong>result</strong> type;
|
|
};
|
|
|
|
struct boost_param_params_ ## __LINE__ ## operator
|
|
: <a class="reference internal" href="#parameters"><tt class="docutils literal">parameters</tt></a><
|
|
<em>list of parameter specifications, based on arguments</em>
|
|
>
|
|
{
|
|
};
|
|
|
|
typedef boost_param_params_ ## __LINE__ ## operator
|
|
boost_param_parameters_ ## __LINE__ ## operator;
|
|
|
|
template <typename A0, …, typename A ## <strong>n</strong>>
|
|
<strong>result</strong> operator()(
|
|
A0&& a0, …, A ## <strong>n</strong>&& a ## <strong>n</strong>
|
|
, typename boost_param_parameters_ ## __LINE__ ## operator::match<
|
|
A0, …, A ## <strong>n</strong>
|
|
>::type = boost_param_parameters_ ## __LINE__ ## operator()
|
|
)
|
|
{
|
|
return this->boost_param_impl ## __LINE__ ## operator(
|
|
boost_param_parameters_ ## __LINE__ ## operator()(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A0>(a0)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>n</strong>>(a ## <strong>n</strong>)
|
|
)
|
|
);
|
|
}
|
|
|
|
<span class="vellipsis">⋮</span>
|
|
|
|
template <typename A0, …, typename A ## <strong>m</strong>>
|
|
<strong>result</strong> operator()(
|
|
A0&& a0, …, A ## <strong>m</strong>&& a ## <strong>m</strong>
|
|
, typename boost_param_parameters_ ## __LINE__ ## operator::match<
|
|
A0, …, A ## <strong>m</strong>
|
|
>::type = boost_param_parameters_ ## __LINE__ ## operator()
|
|
)
|
|
{
|
|
return this->boost_param_impl ## __LINE__ ## operator(
|
|
boost_param_parameters_ ## __LINE__ ## operator()(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A0>(a0)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>m</strong>>(a ## <strong>m</strong>)
|
|
)
|
|
);
|
|
}
|
|
|
|
template <typename Args>
|
|
typename boost_param_result_ ## __LINE__ ## operator<Args>::type
|
|
boost_param_impl ## __LINE__ ## operator(Args const& args)
|
|
{
|
|
return this->boost_param_dispatch_0boost_ ## __LINE__ ## operator(
|
|
static_cast<
|
|
typename boost_param_result_ ## __LINE__ ## operator<
|
|
Args
|
|
>::type(*)()
|
|
>(<a class="reference external" href="http://en.cppreference.com/w/cpp/language/nullptr">std::nullptr</a>)
|
|
, args
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><
|
|
typename <a class="reference internal" href="#value-type"><tt class="docutils literal">value_type</tt></a><
|
|
Args
|
|
, <em>keyword tag type of required parameter</em> ## <strong>0</strong>
|
|
>::type
|
|
>(args[ <em>keyword object of required parameter</em> ## <strong>0</strong>])
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><
|
|
typename <a class="reference internal" href="#value-type"><tt class="docutils literal">value_type</tt></a><
|
|
Args
|
|
, <em>keyword tag type of required parameter</em> ## <strong>n</strong>
|
|
>::type
|
|
>(args[ <em>keyword object of required parameter</em> ## <strong>n</strong>])
|
|
);
|
|
}
|
|
|
|
template <
|
|
typename ResultType
|
|
, typename Args
|
|
, typename <em>argument name</em> ## <strong>0</strong> ## _type
|
|
, …
|
|
, typename <em>argument name</em> ## <strong>n</strong> ## _type
|
|
>
|
|
ResultType
|
|
boost_param_dispatch_0boost_ ## __LINE__ ## operator(
|
|
(ResultType(*)())
|
|
, Args const& args
|
|
, <em>argument name</em> ## <strong>0</strong> ## _type&& <em>argument name</em> ## <strong>0</strong>
|
|
, …
|
|
, <em>argument name</em> ## <strong>n</strong> ## _type&& <em>argument name</em> ## <strong>n</strong>
|
|
)
|
|
{
|
|
return this->boost_param_dispatch_0boost_ ## __LINE__ ## operator(
|
|
static_cast<ResultType(*)()>(<a class="reference external" href="http://en.cppreference.com/w/cpp/language/nullptr">std::nullptr</a>)
|
|
, (args, <em>keyword object of optional parameter</em> ## <strong>n + 1</strong> =
|
|
<em>default value of optional parameter</em> ## <strong>n + 1</strong>
|
|
)
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><<em>argument name</em> ## <strong>0</strong> ## _type>(
|
|
<em>argument name</em> ## <strong>0</strong>
|
|
)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><<em>argument name</em> ## <strong>n</strong> ## _type>(
|
|
<em>argument name</em> ## <strong>n</strong>
|
|
)
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><
|
|
typename <a class="reference internal" href="#value-type"><tt class="docutils literal">value_type</tt></a><
|
|
Args
|
|
, <em>keyword tag type of optional parameter</em> ## <strong>n + 1</strong>
|
|
>::type
|
|
>(<em>default value of optional parameter</em> ## <strong>n + 1</strong>)
|
|
);
|
|
}
|
|
|
|
<span class="vellipsis">⋮</span>
|
|
|
|
template <
|
|
typename ResultType
|
|
, typename Args
|
|
, typename <em>argument name</em> ## <strong>0</strong> ## _type
|
|
, …
|
|
, typename <em>argument name</em> ## <strong>m</strong> ## _type
|
|
>
|
|
ResultType
|
|
boost_param_dispatch_0boost_ ## __LINE__ ## operator(
|
|
(ResultType(*)())
|
|
, Args const& args
|
|
, <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>
|
|
</div>
|
|
<div class="section" id="boost-parameter-const-function-call-operator-result-tag-ns-arguments">
|
|
<span id="boost-parameter-const-function-call-operator"></span><h2><a class="toc-backref" href="#id61">7.5 <tt class="docutils literal">BOOST_PARAMETER_CONST_FUNCTION_CALL_OPERATOR(result, tag_ns, arguments)</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>
|
|
<p>Generates a function call operator that can take in positional arguments,
|
|
composed arguments, named arguments, and deduced 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">Example usage:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>The return type of each of the following function templates falls under a
|
|
different value category.</p>
|
|
<pre class="literal-block">
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> rvalue_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const rvalue_const_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>& lvalue_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> lset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return lset;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const& lvalue_const_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const clset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return clset;
|
|
}
|
|
</pre>
|
|
<p>The <tt class="docutils literal"><span class="pre">U::evaluate_category</span></tt> static member function template has a simple job:
|
|
to return the correct value category when passed in an object returned by one
|
|
of the functions defined above. Assume that
|
|
<a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> is defined.</p>
|
|
<pre class="literal-block">
|
|
enum invoked
|
|
{
|
|
passed_by_lvalue_reference_to_const
|
|
, passed_by_lvalue_reference
|
|
, passed_by_rvalue_reference_to_const
|
|
, passed_by_rvalue_reference
|
|
};
|
|
|
|
struct U
|
|
{
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&)
|
|
{
|
|
return passed_by_lvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&)
|
|
{
|
|
return passed_by_lvalue_reference;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&&)
|
|
{
|
|
return passed_by_rvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&&)
|
|
{
|
|
return passed_by_rvalue_reference;
|
|
}
|
|
};
|
|
</pre>
|
|
<p>Define the named parameters that will comprise the argument specification that
|
|
this macro will use. Ensure that all their tag types are in the same
|
|
namespace, which is <tt class="docutils literal">kw</tt> in this case. The identifiers with leading
|
|
underscores can be passed to the bracket operator of <tt class="docutils literal">args</tt> to extract the
|
|
same argument to which the corresponding named parameter (without underscores)
|
|
is bound, as will be shown later.</p>
|
|
<pre class="literal-block">
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lrc, kw) in(lrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lr, kw) in_out(lr))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rrc, kw) in(rrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rr, kw) consume(rr))
|
|
</pre>
|
|
<p>Use the macro as a substitute for a normal <tt class="docutils literal">const</tt> function call operator
|
|
header. Enclose the return type <tt class="docutils literal">bool</tt> in parentheses. For each parameter,
|
|
also enclose the expected value type in parentheses. Since the value types
|
|
are mutually exclusive, you can wrap the parameters in a <tt class="docutils literal">(deduced …)</tt>
|
|
clause. Otherwise, just as with a normal function, the order in which you
|
|
specify the parameters determines their position. Also, just as with a normal
|
|
function, optional parameters have default values, whereas required parameters
|
|
do not. Within the function body, either simply use the parameter name or
|
|
pass the matching identifier with the leading underscore to the bracket
|
|
operator of <tt class="docutils literal">args</tt> to extract the corresponding argument. Note that the
|
|
second method doesn't require <tt class="docutils literal"><span class="pre">std::forward</span></tt> to preserve value categories.</p>
|
|
<pre class="literal-block">
|
|
struct B
|
|
{
|
|
B()
|
|
{
|
|
}
|
|
|
|
BOOST_PARAMETER_CONST_FUNCTION_CALL_OPERATOR((bool), kw,
|
|
(deduced
|
|
(required
|
|
(lrc, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><1>))
|
|
(lr, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><2>))
|
|
)
|
|
(optional
|
|
(rrc, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><3>), rvalue_const_bitset<2>())
|
|
(rr, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><4>), rvalue_bitset<3>())
|
|
)
|
|
)
|
|
)
|
|
{
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference_to_const
|
|
, U::evaluate_category<0>(lrc)
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference
|
|
, U::evaluate_category<1>(lr)
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference_to_const
|
|
, U::evaluate_category<2>(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><rrc0_type>(rrc0))
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference
|
|
, U::evaluate_category<3>(args[_rr0])
|
|
);
|
|
|
|
return true;
|
|
}
|
|
};
|
|
</pre>
|
|
<p>The following function calls are legal.</p>
|
|
<pre class="literal-block">
|
|
B const b = B();
|
|
b( // positional arguments
|
|
lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
, rvalue_const_bitset<2>()
|
|
, rvalue_bitset<3>()
|
|
);
|
|
b( // positional arguments
|
|
lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
);
|
|
b(( // composed arguments
|
|
_rr0 = rvalue_bitset<3>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
, _lr0 = lvalue_bitset<1>()
|
|
, _rrc0 = rvalue_const_bitset<2>()
|
|
));
|
|
b( // named arguments
|
|
_rr0 = rvalue_bitset<3>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
, _lr0 = lvalue_bitset<1>()
|
|
, _rrc0 = rvalue_const_bitset<2>()
|
|
);
|
|
b( // named arguments
|
|
_lr0 = lvalue_bitset<1>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
);
|
|
</pre>
|
|
<p>Because the parameters were wrapped in a <tt class="docutils literal">(deduced …)</tt> clause, the following
|
|
function calls are also legal.</p>
|
|
<pre class="literal-block">
|
|
b( // deduced arguments
|
|
rvalue_bitset<3>()
|
|
, lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
, rvalue_const_bitset<2>()
|
|
);
|
|
b( // deduced arguments
|
|
lvalue_bitset<1>()
|
|
, lvalue_const_bitset<0>()
|
|
);
|
|
</pre>
|
|
<p>The <a class="reference external" href="../../test/preprocessor.cpp">preprocessor.cpp</a>, <a class="reference external" href="../../test/preprocessor_deduced.cpp">preprocessor_deduced.cpp</a>, and
|
|
<a class="reference external" href="../../test/preprocessor_eval_cat_8.cpp">preprocessor_eval_cat_8.cpp</a> test programs demonstrate proper usage of this
|
|
macro.</p>
|
|
<p><strong>Macro parameters:</strong></p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">result</tt> is the parenthesized return type of the function call operator.</li>
|
|
<li><tt class="docutils literal">tag_namespace</tt> is the namespace in which the keywords used by the
|
|
function call operator resides.</li>
|
|
<li><tt class="docutils literal">arguments</tt> is a <a class="reference external" href="../../../preprocessor/doc/index.html">Boost.Preprocessor</a> <a class="reference external" href="../../../preprocessor/doc/data/sequences.html">sequence</a> of
|
|
<em>argument-specifiers</em>, as defined below.</li>
|
|
</ul>
|
|
<p><strong>Argument specifiers syntax:</strong></p>
|
|
<pre class="literal-block">
|
|
argument-specifiers ::= <em>specifier-group0</em> {<em>specifier-group0</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>argument-name</em> '<strong>,</strong>' <em>restriction</em> '<strong>,</strong>' <em>default-value</em>
|
|
')'
|
|
|
|
required-specifier ::=
|
|
'<strong>(</strong>' <em>argument-name</em> '<strong>,</strong>' <em>restriction</em> ')'
|
|
|
|
restriction ::=
|
|
( '<strong>*</strong>' '<strong>(</strong>' <em>mfc</em> '<strong>)</strong>' ) |
|
|
( '<strong>(</strong>' <em>type-name</em> '<strong>)</strong>' ) |
|
|
'<strong>*</strong>'
|
|
</pre>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal"><span class="pre">argument-name</span></tt> is any valid C++ identifier.</li>
|
|
<li><tt class="docutils literal"><span class="pre">default-value</span></tt> is any valid C++ expression; if necessary, user code can
|
|
compute it in terms of <tt class="docutils literal"><span class="pre">previous-name</span> ## _type</tt>, where <tt class="docutils literal"><span class="pre">previous-name</span></tt>
|
|
is the <tt class="docutils literal"><span class="pre">argument-name</span></tt> in a previous <tt class="docutils literal"><span class="pre">specifier-group0</span></tt> or
|
|
<tt class="docutils literal"><span class="pre">specifier-group1</span></tt>. <em>This expression will be invoked exactly once.</em></li>
|
|
<li><tt class="docutils literal">mfc</tt> is an <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary Metafunction Class</a> whose first argument will
|
|
be the type of the corresponding <tt class="docutils literal"><span class="pre">argument-name</span></tt>, whose second argument
|
|
will be the entire <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>, and whose return type is a <a class="reference external" href="../../../mpl/doc/refmanual/integral-constant.html">Boolean
|
|
Integral Constant</a>; however, user code <em>cannot</em> compute <tt class="docutils literal">mfc</tt> in terms
|
|
of <tt class="docutils literal"><span class="pre">previous-name</span> ## _type</tt>.</li>
|
|
<li><tt class="docutils literal"><span class="pre">type-name</span></tt> is either the name of a <strong>target type</strong> or an <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary
|
|
Metafunction Class</a> whose first argument will be the type of the
|
|
corresponding <tt class="docutils literal"><span class="pre">argument-name</span></tt>, whose second argument will be the entire
|
|
<a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>, and whose return type is the <strong>target type</strong>. If
|
|
<tt class="docutils literal">restriction</tt> uses this form, then the type of the generated name
|
|
<tt class="docutils literal"><span class="pre">argument-name</span> ## _type</tt> will be computed in terms of the <strong>target
|
|
type</strong>, and the generated reference <tt class="docutils literal"><span class="pre">argument-name</span></tt> (but not its
|
|
corresponding entry in <tt class="docutils literal">args</tt>) will be cast to that type.</li>
|
|
</ul>
|
|
<p><strong>Approximate expansion:</strong></p>
|
|
<p>Where:</p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">n</tt> denotes the <em>minimum</em> arity, as determined from <tt class="docutils literal">arguments</tt>.</li>
|
|
<li><tt class="docutils literal">m</tt> denotes the <em>maximum</em> arity, as determined from <tt class="docutils literal">arguments</tt>.</li>
|
|
</ul>
|
|
<pre class="literal-block">
|
|
// If <strong>result</strong> is a template instantiation of <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if_c</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if_c</a>, or
|
|
// <a class="reference external" href="http://en.cppreference.com/w/cpp/types/enable_if">std::enable_if</a>:
|
|
template <typename Args>
|
|
using boost_param_result_const_ ## __LINE__ ## operator = <strong>result</strong>;
|
|
|
|
// If <strong>result</strong> is a simple return type:
|
|
template <typename Args>
|
|
struct boost_param_result_const_ ## __LINE__ ## operator
|
|
{
|
|
typedef <strong>result</strong> type;
|
|
};
|
|
|
|
struct boost_param_params_const_ ## __LINE__ ## operator
|
|
: <a class="reference internal" href="#parameters"><tt class="docutils literal">parameters</tt></a><
|
|
<em>list of parameter specifications, based on arguments</em>
|
|
>
|
|
{
|
|
};
|
|
|
|
typedef boost_param_params_const_ ## __LINE__ ## operator
|
|
boost_param_parameters_const_ ## __LINE__ ## operator;
|
|
|
|
template <typename A0, …, typename A ## <strong>n</strong>>
|
|
<strong>result</strong> operator()(
|
|
A0&& a0, …, A ## <strong>n</strong>&& a ## <strong>n</strong>
|
|
, typename boost_param_parameters_const_ ## __LINE__ ## operator
|
|
::match<A0, …, A ## <strong>n</strong>>::type
|
|
= boost_param_parameters_const_ ## __LINE__ ## operator()
|
|
) const
|
|
{
|
|
return this->boost_param_impl_const ## __LINE__ ## operator(
|
|
boost_param_parameters_const_ ## __LINE__ ## operator()(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A0>(a0)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>n</strong>>(a ## <strong>n</strong>)
|
|
)
|
|
);
|
|
}
|
|
|
|
<span class="vellipsis">⋮</span>
|
|
|
|
template <typename A0, …, typename A ## <strong>m</strong>>
|
|
<strong>result</strong> operator()(
|
|
A0&& a0, …, A ## <strong>m</strong>&& a ## <strong>m</strong>
|
|
, typename boost_param_parameters_const_ ## __LINE__ ## operator
|
|
::match<A0, …, A ## <strong>m</strong>>::type
|
|
= boost_param_parameters_const_ ## __LINE__ ## operator()
|
|
) const
|
|
{
|
|
return this->boost_param_impl_const ## __LINE__ ## operator(
|
|
boost_param_parameters_const_ ## __LINE__ ## operator()(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A0>(a0)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>m</strong>>(a ## <strong>m</strong>)
|
|
)
|
|
);
|
|
}
|
|
|
|
template <typename Args>
|
|
typename boost_param_result_const_ ## __LINE__ ## operator<Args>::type
|
|
boost_param_impl_const ## __LINE__ ## operator(Args const& args) const
|
|
{
|
|
return this->
|
|
boost_param_dispatch_const_0boost_ ## __LINE__ ## operator(
|
|
static_cast<
|
|
typename boost_param_result_const_ ## __LINE__ ## operator<
|
|
Args
|
|
>::type(*)()
|
|
>(<a class="reference external" href="http://en.cppreference.com/w/cpp/language/nullptr">std::nullptr</a>)
|
|
, args
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><
|
|
typename <a class="reference internal" href="#value-type"><tt class="docutils literal">value_type</tt></a><
|
|
Args
|
|
, <em>keyword tag type of required parameter</em> ## <strong>0</strong>
|
|
>::type
|
|
>(args[ <em>keyword object of required parameter</em> ## <strong>0</strong>])
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><
|
|
typename <a class="reference internal" href="#value-type"><tt class="docutils literal">value_type</tt></a><
|
|
Args
|
|
, <em>keyword tag type of required parameter</em> ## <strong>n</strong>
|
|
>::type
|
|
>(args[ <em>keyword object of required parameter</em> ## <strong>n</strong>])
|
|
);
|
|
}
|
|
|
|
template <
|
|
typename ResultType
|
|
, typename Args
|
|
, typename <em>argument name</em> ## <strong>0</strong> ## _type
|
|
, …
|
|
, typename <em>argument name</em> ## <strong>n</strong> ## _type
|
|
>
|
|
ResultType
|
|
boost_param_dispatch_const_0boost_ ## __LINE__ ## operator(
|
|
(ResultType(*)())
|
|
, Args const& args
|
|
, <em>argument name</em> ## <strong>0</strong> ## _type&& <em>argument name</em> ## <strong>0</strong>
|
|
, …
|
|
, <em>argument name</em> ## <strong>n</strong> ## _type&& <em>argument name</em> ## <strong>n</strong>
|
|
) const
|
|
{
|
|
return this->
|
|
boost_param_dispatch_const_0boost_ ## __LINE__ ## operator(
|
|
static_cast<ResultType(*)()>(<a class="reference external" href="http://en.cppreference.com/w/cpp/language/nullptr">std::nullptr</a>)
|
|
, (args, <em>keyword object of optional parameter</em> ## <strong>n + 1</strong> =
|
|
<em>default value of optional parameter</em> ## <strong>n + 1</strong>
|
|
)
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><<em>argument name</em> ## <strong>0</strong> ## _type>(
|
|
<em>argument name</em> ## <strong>0</strong>
|
|
)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><<em>argument name</em> ## <strong>n</strong> ## _type>(
|
|
<em>argument name</em> ## <strong>n</strong>
|
|
)
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><
|
|
typename <a class="reference internal" href="#value-type"><tt class="docutils literal">value_type</tt></a><
|
|
Args
|
|
, <em>keyword tag type of optional parameter</em> ## <strong>n + 1</strong>
|
|
>::type
|
|
>(<em>default value of optional parameter</em> ## <strong>n + 1</strong>)
|
|
);
|
|
}
|
|
|
|
<span class="vellipsis">⋮</span>
|
|
|
|
template <
|
|
typename ResultType
|
|
, typename Args
|
|
, typename <em>argument name</em> ## <strong>0</strong> ## _type
|
|
, …
|
|
, typename <em>argument name</em> ## <strong>m</strong> ## _type
|
|
>
|
|
ResultType
|
|
boost_param_dispatch_const_0boost_ ## __LINE__ ## operator(
|
|
(ResultType(*)())
|
|
, Args const& args
|
|
, <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>
|
|
) const
|
|
</pre>
|
|
</div>
|
|
<div class="section" id="boost-parameter-constructor-cls-impl-tag-namespace-arguments">
|
|
<span id="boost-parameter-constructor"></span><h2><a class="toc-backref" href="#id62">7.6 <tt class="docutils literal">BOOST_PARAMETER_CONSTRUCTOR(cls, impl, tag_namespace, arguments)</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>
|
|
<p>Generates a constructor that can take in positional arguments, composed
|
|
arguments, named arguments, and deduced 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">Example usage:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>Define the named parameters that will comprise the argument specification that
|
|
this macro will use. Ensure that all their tag types are in the same
|
|
namespace, which is <tt class="docutils literal">tag</tt> by default.</p>
|
|
<pre class="literal-block">
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>(y)
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>(z)
|
|
</pre>
|
|
<p>In the base class, implement a delegate constructor template that takes in an
|
|
<a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>. You must pass the identifiers with leading underscores to
|
|
<tt class="docutils literal">args</tt> in order to extract the corresponding arguments.</p>
|
|
<pre class="literal-block">
|
|
class char_read_base
|
|
{
|
|
int index;
|
|
char const* key;
|
|
|
|
public:
|
|
template <typename Args>
|
|
explicit char_read_base(Args const& args)
|
|
: index(args[_y]), key(args[_z])
|
|
{
|
|
}
|
|
|
|
<a class="reference internal" href="#boost-parameter-const-function-call-operator"><tt class="docutils literal">BOOST_PARAMETER_CONST_FUNCTION_CALL_OPERATOR</tt></a>((char), tag,
|
|
(deduced
|
|
(required
|
|
(y, (bool))
|
|
(z, (<a class="reference external" href="http://en.cppreference.com/w/cpp/container/map">std::map</a><char const*, <a class="reference external" href="http://en.cppreference.com/w/cpp/string/basic_string">std::string</a>>))
|
|
)
|
|
)
|
|
)
|
|
{
|
|
return y ? (
|
|
(z.find(this->key)->second)[this->index]
|
|
) : this->key[this->index];
|
|
}
|
|
};
|
|
</pre>
|
|
<p>Use the macro as a substitute for a normal constructor definition. Note the
|
|
lack of an explicit body. Enclose the base type in parentheses. For each
|
|
parameter, also enclose the expected value type in parentheses. Since the
|
|
value types are mutually exclusive, you can wrap the parameters in a
|
|
<tt class="docutils literal">(deduced …)</tt> clause.</p>
|
|
<pre class="literal-block">
|
|
struct char_reader : public char_read_base
|
|
{
|
|
BOOST_PARAMETER_CONSTRUCTOR(char_reader, (char_read_base), tag,
|
|
(deduced
|
|
(required
|
|
(y, (int))
|
|
(z, (char const*))
|
|
)
|
|
)
|
|
)
|
|
};
|
|
</pre>
|
|
<p>The following <tt class="docutils literal">char_reader</tt> constructor calls are legal.</p>
|
|
<pre class="literal-block">
|
|
char const* keys[] = {"foo", "bar", "baz"};
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/container/map">std::map</a><char const*, <a class="reference external" href="http://en.cppreference.com/w/cpp/string/basic_string">std::string</a>> k2s;
|
|
k2s[keys[0]] = <a class="reference external" href="http://en.cppreference.com/w/cpp/string/basic_string">std::string</a>("qux");
|
|
k2s[keys[1]] = <a class="reference external" href="http://en.cppreference.com/w/cpp/string/basic_string">std::string</a>("wmb");
|
|
k2s[keys[2]] = <a class="reference external" href="http://en.cppreference.com/w/cpp/string/basic_string">std::string</a>("zxc");
|
|
|
|
// positional arguments
|
|
char_reader r0(0, keys[0]);
|
|
BOOST_TEST_EQ('q', (r0(true, k2s)));
|
|
BOOST_TEST_EQ('f', (r0(false, k2s)));
|
|
|
|
// named arguments
|
|
char_reader r1(_z = keys[1], _y = 1);
|
|
BOOST_TEST_EQ('m', (r1(_z = k2s, _y = true)));
|
|
BOOST_TEST_EQ('a', (r1(_z = k2s, _y = false)));
|
|
|
|
// deduced arguments
|
|
char_reader r2(keys[2], 2);
|
|
BOOST_TEST_EQ('c', (r2(k2s, true)));
|
|
BOOST_TEST_EQ('z', (r2(k2s, false)));
|
|
</pre>
|
|
<p>The <a class="reference external" href="../../test/preprocessor.cpp">preprocessor.cpp</a> and <a class="reference external" href="../../test/preprocessor_deduced.cpp">preprocessor_deduced.cpp</a> test programs
|
|
demonstrate proper usage of this macro.</p>
|
|
<p><strong>Macro parameters:</strong></p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">cls</tt> is the name of the enclosing class.</li>
|
|
<li><tt class="docutils literal">impl</tt> is the parenthesized implementation base class for <tt class="docutils literal">cls</tt>.</li>
|
|
<li><tt class="docutils literal">tag_namespace</tt> is the namespace in which the keywords used by the
|
|
constructor resides.</li>
|
|
<li><tt class="docutils literal">arguments</tt> is a list of <em>argument-specifiers</em>, as defined below.</li>
|
|
</ul>
|
|
<p><strong>Argument specifiers syntax:</strong></p>
|
|
<pre class="literal-block">
|
|
argument-specifiers ::= <em>specifier-group0</em> {<em>specifier-group0</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>specifier</em> {<em>specifier</em>}
|
|
'<strong>)</strong>'
|
|
) | (
|
|
'<strong>(</strong>' '<strong>required</strong>'
|
|
<em>specifier</em> {<em>specifier</em>}
|
|
'<strong>)</strong>'
|
|
)
|
|
|
|
specifier ::=
|
|
'<strong>(</strong>' <em>argument-name</em> '<strong>,</strong>' <em>restriction</em> ')'
|
|
|
|
restriction ::=
|
|
( '<strong>*</strong>' '<strong>(</strong>' <em>mfc</em> '<strong>)</strong>' ) |
|
|
( '<strong>(</strong>' <em>type-name</em> '<strong>)</strong>' ) |
|
|
'<strong>*</strong>'
|
|
</pre>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal"><span class="pre">argument-name</span></tt> is any valid C++ identifier.</li>
|
|
<li><tt class="docutils literal">mfc</tt> is an <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary Metafunction Class</a> whose first argument will
|
|
be the type of the corresponding <tt class="docutils literal"><span class="pre">argument-name</span></tt>, whose second argument
|
|
will be the entire <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>, and whose return type is a <a class="reference external" href="../../../mpl/doc/refmanual/integral-constant.html">Boolean
|
|
Integral Constant</a>; however, user code <em>cannot</em> compute <tt class="docutils literal">mfc</tt> in terms
|
|
of <tt class="docutils literal"><span class="pre">previous-name</span> ## _type</tt>.</li>
|
|
<li><tt class="docutils literal"><span class="pre">type-name</span></tt> is either the name of a <strong>target type</strong> or an <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary
|
|
Metafunction Class</a> whose first argument will be the type of the
|
|
corresponding <tt class="docutils literal"><span class="pre">argument-name</span></tt>, whose second argument will be the entire
|
|
<a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>, and whose return type is the <strong>target type</strong>.</li>
|
|
</ul>
|
|
<p>Note that <em>specifier</em> does not include <em>default-value</em>. It is up to the
|
|
delegate constructor in <tt class="docutils literal">impl</tt> to determine the default value of all
|
|
optional arguments.</p>
|
|
<p><strong>Approximate expansion:</strong></p>
|
|
<p>Where:</p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">n</tt> denotes the <em>minimum</em> arity, as determined from <tt class="docutils literal">arguments</tt>.</li>
|
|
<li><tt class="docutils literal">m</tt> denotes the <em>maximum</em> arity, as determined from <tt class="docutils literal">arguments</tt>.</li>
|
|
</ul>
|
|
<pre class="literal-block">
|
|
struct boost_param_params_ ## __LINE__ ## ctor
|
|
: <a class="reference internal" href="#parameters"><tt class="docutils literal">parameters</tt></a><
|
|
<em>list of parameter specifications, based on arguments</em>
|
|
>
|
|
{
|
|
};
|
|
|
|
typedef boost_param_params_ ## __LINE__ ## ctor
|
|
constructor_parameters ## __LINE__;
|
|
|
|
template <typename A0, …, typename A ## <strong>n</strong>>
|
|
<strong>cls</strong>(A0&& a0, …, A ## <strong>n</strong> && a ## <strong>n</strong>)
|
|
: <strong>impl</strong>(
|
|
constructor_parameters ## __LINE__(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A0>(a0)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>n</strong>>(a ## <strong>n</strong>)
|
|
)
|
|
)
|
|
{
|
|
}
|
|
|
|
<span class="vellipsis">⋮</span>
|
|
|
|
template <typename A0, …, typename A ## <strong>m</strong>>
|
|
<strong>cls</strong>(A0&& a0, …, A ## <strong>m</strong> && a ## <strong>m</strong>)
|
|
: <strong>impl</strong>(
|
|
constructor_parameters ## __LINE__(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A0>(a0)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>m</strong>>(a ## <strong>m</strong>)
|
|
)
|
|
)
|
|
{
|
|
}
|
|
</pre>
|
|
</div>
|
|
<div class="section" id="boost-parameter-basic-function-result-name-tag-namespace-arguments">
|
|
<span id="boost-parameter-basic-function"></span><h2><a class="toc-backref" href="#id63">7.7 <tt class="docutils literal">BOOST_PARAMETER_BASIC_FUNCTION(result, name, tag_namespace, arguments)</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>
|
|
<p>Generates a function that can take in positional arguments, composed
|
|
arguments, named arguments, and deduced 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">Example usage:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>The return type of each of the following function templates falls under a
|
|
different value category.</p>
|
|
<pre class="literal-block">
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> rvalue_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const rvalue_const_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>& lvalue_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> lset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return lset;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const& lvalue_const_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const clset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return clset;
|
|
}
|
|
</pre>
|
|
<p>The <tt class="docutils literal"><span class="pre">U::evaluate_category</span></tt> static member function template has a simple job:
|
|
to return the correct value category when passed in an object returned by one
|
|
of the functions defined above. Assume that
|
|
<a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> is defined.</p>
|
|
<pre class="literal-block">
|
|
enum invoked
|
|
{
|
|
passed_by_lvalue_reference_to_const
|
|
, passed_by_lvalue_reference
|
|
, passed_by_rvalue_reference_to_const
|
|
, passed_by_rvalue_reference
|
|
};
|
|
|
|
struct U
|
|
{
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&)
|
|
{
|
|
return passed_by_lvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&)
|
|
{
|
|
return passed_by_lvalue_reference;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&&)
|
|
{
|
|
return passed_by_rvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&&)
|
|
{
|
|
return passed_by_rvalue_reference;
|
|
}
|
|
};
|
|
</pre>
|
|
<p>Define the named parameters that will comprise the argument specification that
|
|
this macro will use. Ensure that all their tag types are in the same
|
|
namespace, which is <tt class="docutils literal">kw</tt> in this case. The identifiers with leading
|
|
underscores can be passed to the bracket operator of <tt class="docutils literal">args</tt> to extract the
|
|
same argument to which the corresponding named parameter (without underscores)
|
|
is bound, as will be shown later.</p>
|
|
<pre class="literal-block">
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lrc, kw) in(lrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lr, kw) in_out(lr))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rrc, kw) in(rrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rr, kw) consume(rr))
|
|
</pre>
|
|
<p>Use the macro as a substitute for a normal function header. Enclose the
|
|
return type <tt class="docutils literal">bool</tt> in parentheses. For each parameter, also enclose the
|
|
expected value type in parentheses. Since the value types are mutually
|
|
exclusive, you can wrap the parameters in a <tt class="docutils literal">(deduced …)</tt>
|
|
clause. Otherwise, just as with a normal function, the order in which you
|
|
specify the parameters determines their position. However, unlike a normal
|
|
function, default values must be specified within the function body. Also
|
|
within the function body, you must pass the matching identifier with the
|
|
leading underscore to the bracket operator of <tt class="docutils literal">args</tt> to extract the
|
|
corresponding argument, but at least this doesn't require <tt class="docutils literal"><span class="pre">std::forward</span></tt> to
|
|
preserve value categories.</p>
|
|
<pre class="literal-block">
|
|
BOOST_PARAMETER_BASIC_FUNCTION((bool), evaluate, kw,
|
|
(deduced
|
|
(required
|
|
(lrc, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><1>))
|
|
(lr, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><2>))
|
|
)
|
|
(optional
|
|
(rrc, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><3>))
|
|
(rr, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><4>))
|
|
)
|
|
)
|
|
)
|
|
{
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference_to_const
|
|
, U::evaluate_category<0>(args[_lrc])
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference
|
|
, U::evaluate_category<1>(args[_lr])
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference_to_const
|
|
, U::evaluate_category<2>(
|
|
args[_rrc0 | rvalue_const_bitset<2>()]
|
|
)
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference
|
|
, U::evaluate_category<3>(args[_rr0 | rvalue_bitset<3>()])
|
|
);
|
|
|
|
return true;
|
|
}
|
|
</pre>
|
|
<p>The following function calls are legal.</p>
|
|
<pre class="literal-block">
|
|
evaluate( // positional arguments
|
|
lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
, rvalue_const_bitset<2>()
|
|
, rvalue_bitset<3>()
|
|
);
|
|
evaluate( // positional arguments
|
|
lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
);
|
|
evaluate(( // composed arguments
|
|
_rr0 = rvalue_bitset<3>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
, _lr0 = lvalue_bitset<1>()
|
|
, _rrc0 = rvalue_const_bitset<2>()
|
|
));
|
|
evaluate( // named arguments
|
|
_rr0 = rvalue_bitset<3>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
, _lr0 = lvalue_bitset<1>()
|
|
, _rrc0 = rvalue_const_bitset<2>()
|
|
);
|
|
evaluate( // named arguments
|
|
_lr0 = lvalue_bitset<1>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
);
|
|
</pre>
|
|
<p>Because the parameters were wrapped in a <tt class="docutils literal">(deduced …)</tt> clause, the following
|
|
function calls are also legal.</p>
|
|
<pre class="literal-block">
|
|
evaluate( // deduced arguments
|
|
rvalue_bitset<3>()
|
|
, lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
, rvalue_const_bitset<2>()
|
|
);
|
|
evaluate( // deduced arguments
|
|
lvalue_bitset<1>()
|
|
, lvalue_const_bitset<0>()
|
|
);
|
|
</pre>
|
|
<p>The <a class="reference external" href="../../test/preprocessor.cpp">preprocessor.cpp</a> test program demonstrates proper usage of this macro.</p>
|
|
<p><strong>Macro parameters:</strong></p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">result</tt> is the parenthesized return type of the function.</li>
|
|
<li><tt class="docutils literal">name</tt> is the base name of the function; it determines the name of the
|
|
generated forwarding functions.</li>
|
|
<li><tt class="docutils literal">tag_namespace</tt> is the namespace in which the keywords used by the
|
|
function resides.</li>
|
|
<li><tt class="docutils literal">arguments</tt> is a <a class="reference external" href="../../../preprocessor/doc/index.html">Boost.Preprocessor</a> <a class="reference external" href="../../../preprocessor/doc/data/sequences.html">sequence</a> of
|
|
<em>argument-specifiers</em>, as defined below.</li>
|
|
</ul>
|
|
<p><strong>Argument specifiers syntax:</strong></p>
|
|
<pre class="literal-block">
|
|
argument-specifiers ::= <em>specifier-group0</em> {<em>specifier-group0</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>specifier</em> {<em>specifier</em>}
|
|
'<strong>)</strong>'
|
|
) | (
|
|
'<strong>(</strong>' '<strong>required</strong>'
|
|
<em>specifier</em> {<em>specifier</em>}
|
|
'<strong>)</strong>'
|
|
)
|
|
|
|
specifier ::=
|
|
'<strong>(</strong>' <em>argument-name</em> '<strong>,</strong>' <em>restriction</em> ')'
|
|
|
|
restriction ::=
|
|
( '<strong>*</strong>' '<strong>(</strong>' <em>mfc</em> '<strong>)</strong>' ) |
|
|
( '<strong>(</strong>' <em>type-name</em> '<strong>)</strong>' ) |
|
|
'<strong>*</strong>'
|
|
</pre>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal"><span class="pre">argument-name</span></tt> is any valid C++ identifier.</li>
|
|
<li><tt class="docutils literal">mfc</tt> is an <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary Metafunction Class</a> whose first argument will
|
|
be the type of the corresponding <tt class="docutils literal"><span class="pre">argument-name</span></tt>, whose second argument
|
|
will be the entire <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>, and whose return type is a <a class="reference external" href="../../../mpl/doc/refmanual/integral-constant.html">Boolean
|
|
Integral Constant</a>; however, user code <em>cannot</em> compute <tt class="docutils literal">mfc</tt> in terms
|
|
of <tt class="docutils literal"><span class="pre">previous-name</span> ## _type</tt>.</li>
|
|
<li><tt class="docutils literal"><span class="pre">type-name</span></tt> is either the name of a <strong>target type</strong> or an <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary
|
|
Metafunction Class</a> whose first argument will be the type of the
|
|
corresponding <tt class="docutils literal"><span class="pre">argument-name</span></tt>, whose second argument will be the entire
|
|
<a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>, and whose return type is the <strong>target type</strong>.</li>
|
|
</ul>
|
|
<p>Note that <em>specifier</em> does not include <em>default-value</em>. It is up to the
|
|
function body to determine the default value of all optional arguments.</p>
|
|
<p><strong>Approximate expansion:</strong></p>
|
|
<p>Where:</p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">n</tt> denotes the <em>minimum</em> arity, as determined from <tt class="docutils literal">arguments</tt>.</li>
|
|
<li><tt class="docutils literal">m</tt> denotes the <em>maximum</em> arity, as determined from <tt class="docutils literal">arguments</tt>.</li>
|
|
</ul>
|
|
<pre class="literal-block">
|
|
// If <strong>result</strong> is a template instantiation of <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if_c</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if_c</a>, or
|
|
// <a class="reference external" href="http://en.cppreference.com/w/cpp/types/enable_if">std::enable_if</a>:
|
|
template <typename Args>
|
|
using boost_param_result_ ## __LINE__ ## <strong>name</strong> = <strong>result</strong>;
|
|
|
|
// If <strong>result</strong> is a simple return type:
|
|
template <typename Args>
|
|
struct boost_param_result_ ## __LINE__ ## <strong>name</strong>
|
|
{
|
|
typedef <strong>result</strong> type;
|
|
};
|
|
|
|
struct boost_param_params_ ## __LINE__ ## <strong>name</strong>
|
|
: <a class="reference internal" href="#parameters"><tt class="docutils literal">parameters</tt></a><
|
|
<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 <typename Args>
|
|
typename boost_param_result_ ## __LINE__ ## <strong>name</strong><Args>::type
|
|
boost_param_impl ## <strong>name</strong>(Args const&);
|
|
|
|
template <typename A0, …, typename A ## <strong>n</strong>>
|
|
<strong>result</strong> <strong>name</strong>(
|
|
A0&& a0, …, A ## <strong>n</strong>&& a ## <strong>n</strong>
|
|
, typename boost_param_parameters_ ## __LINE__ ## <strong>name</strong>
|
|
::match<A0, …, A ## <strong>n</strong>>::type
|
|
= boost_param_parameters_ ## __LINE__ ## <strong>name</strong>()
|
|
)
|
|
{
|
|
return boost_param_impl ## __LINE__ ## <strong>name</strong>(
|
|
boost_param_parameters_ ## __LINE__ ## <strong>name</strong>()(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A0>(a0)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>n</strong>>(a ## <strong>n</strong>)
|
|
)
|
|
);
|
|
}
|
|
|
|
<span class="vellipsis">⋮</span>
|
|
|
|
template <typename A0, …, typename A ## <strong>m</strong>>
|
|
<strong>result</strong> <strong>name</strong>(
|
|
A0&& a0, …, A ## <strong>m</strong>&& a ## <strong>m</strong>
|
|
, typename boost_param_parameters_ ## __LINE__ ## <strong>name</strong>
|
|
::match<A0, …, A ## <strong>m</strong>>::type
|
|
= boost_param_parameters_ ## __LINE__ ## <strong>name</strong>()
|
|
)
|
|
{
|
|
return boost_param_impl ## __LINE__ ## <strong>name</strong>(
|
|
boost_param_parameters_ ## __LINE__ ## <strong>name</strong>()(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A0>(a0)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>m</strong>>(a ## <strong>m</strong>)
|
|
)
|
|
);
|
|
}
|
|
|
|
template <typename Args>
|
|
typename boost_param_result_ ## __LINE__ ## <strong>name</strong><Args>::type
|
|
boost_param_impl ## __LINE__ ## <strong>name</strong>(Args const& args)
|
|
</pre>
|
|
<p>Only the <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> type <tt class="docutils literal">Args</tt> and its object instance <tt class="docutils literal">args</tt> are
|
|
available for use within the function body.</p>
|
|
</div>
|
|
<div class="section" id="boost-parameter-basic-member-function-result-name-tag-ns-arguments">
|
|
<span id="boost-parameter-basic-member-function"></span><h2><a class="toc-backref" href="#id64">7.8 <tt class="docutils literal">BOOST_PARAMETER_BASIC_MEMBER_FUNCTION(result, name, tag_ns, arguments)</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>
|
|
<p>Generates a member function that can take in positional arguments, composed
|
|
arguments, named arguments, and deduced 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">Example usage:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>The return type of each of the following function templates falls under a
|
|
different value category.</p>
|
|
<pre class="literal-block">
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> rvalue_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const rvalue_const_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>& lvalue_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> lset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return lset;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const& lvalue_const_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const clset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return clset;
|
|
}
|
|
</pre>
|
|
<p>The <tt class="docutils literal"><span class="pre">U::evaluate_category</span></tt> static member function template has a simple job:
|
|
to return the correct value category when passed in an object returned by one
|
|
of the functions defined above. Assume that
|
|
<a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> is defined.</p>
|
|
<pre class="literal-block">
|
|
enum invoked
|
|
{
|
|
passed_by_lvalue_reference_to_const
|
|
, passed_by_lvalue_reference
|
|
, passed_by_rvalue_reference_to_const
|
|
, passed_by_rvalue_reference
|
|
};
|
|
|
|
struct U
|
|
{
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&)
|
|
{
|
|
return passed_by_lvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&)
|
|
{
|
|
return passed_by_lvalue_reference;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&&)
|
|
{
|
|
return passed_by_rvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&&)
|
|
{
|
|
return passed_by_rvalue_reference;
|
|
}
|
|
};
|
|
</pre>
|
|
<p>Define the named parameters that will comprise the argument specification that
|
|
this macro will use. Ensure that all their tag types are in the same
|
|
namespace, which is <tt class="docutils literal">kw</tt> in this case. The identifiers with leading
|
|
underscores can be passed to the bracket operator of <tt class="docutils literal">args</tt> to extract the
|
|
same argument to which the corresponding named parameter (without underscores)
|
|
is bound, as will be shown later.</p>
|
|
<pre class="literal-block">
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lrc, kw) in(lrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lr, kw) in_out(lr))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rrc, kw) in(rrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rr, kw) consume(rr))
|
|
</pre>
|
|
<p>Use the macro as a substitute for a normal <tt class="docutils literal">static</tt> member function
|
|
header. Enclose the return type <tt class="docutils literal">bool</tt> in parentheses. For each parameter,
|
|
also enclose the expected value type in parentheses. Since the value types
|
|
are mutually exclusive, you can wrap the parameters in a <tt class="docutils literal">(deduced …)</tt>
|
|
clause. Otherwise, just as with a normal function, the order in which you
|
|
specify the parameters determines their position. However, unlike a normal
|
|
function, default values must be specified within the function body. Also
|
|
within the function body, you must pass the matching identifier with the
|
|
leading underscore to the bracket operator of <tt class="docutils literal">args</tt> to extract the
|
|
corresponding argument, but at least this doesn't require <tt class="docutils literal"><span class="pre">std::forward</span></tt> to
|
|
preserve value categories.</p>
|
|
<pre class="literal-block">
|
|
struct B
|
|
{
|
|
BOOST_PARAMETER_BASIC_MEMBER_FUNCTION((bool), static evaluate, kw,
|
|
(deduced
|
|
(required
|
|
(lrc, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><1>))
|
|
(lr, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><2>))
|
|
)
|
|
(optional
|
|
(rrc, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><3>))
|
|
(rr, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><4>))
|
|
)
|
|
)
|
|
)
|
|
{
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference_to_const
|
|
, U::evaluate_category<0>(args[_lrc])
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference
|
|
, U::evaluate_category<1>(args[_lr])
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference_to_const
|
|
, U::evaluate_category<2>(
|
|
args[_rrc0 | rvalue_const_bitset<2>()]
|
|
)
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference
|
|
, U::evaluate_category<3>(
|
|
args[_rr0 | rvalue_bitset<3>()]
|
|
)
|
|
);
|
|
|
|
return true;
|
|
}
|
|
};
|
|
</pre>
|
|
<p>The following function calls are legal.</p>
|
|
<pre class="literal-block">
|
|
B::evaluate( // positional arguments
|
|
lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
, rvalue_const_bitset<2>()
|
|
, rvalue_bitset<3>()
|
|
);
|
|
B::evaluate( // positional arguments
|
|
lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
);
|
|
B::evaluate(( // composed arguments
|
|
_rr0 = rvalue_bitset<3>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
, _lr0 = lvalue_bitset<1>()
|
|
, _rrc0 = rvalue_const_bitset<2>()
|
|
));
|
|
B::evaluate( // named arguments
|
|
_rr0 = rvalue_bitset<3>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
, _lr0 = lvalue_bitset<1>()
|
|
, _rrc0 = rvalue_const_bitset<2>()
|
|
);
|
|
B::evaluate( // named arguments
|
|
_lr0 = lvalue_bitset<1>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
);
|
|
</pre>
|
|
<p>Because the parameters were wrapped in a <tt class="docutils literal">(deduced …)</tt> clause, the following
|
|
function calls are also legal.</p>
|
|
<pre class="literal-block">
|
|
B::evaluate( // deduced arguments
|
|
rvalue_bitset<3>()
|
|
, lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
, rvalue_const_bitset<2>()
|
|
);
|
|
B::evaluate( // deduced arguments
|
|
lvalue_bitset<1>()
|
|
, lvalue_const_bitset<0>()
|
|
);
|
|
</pre>
|
|
<p>The <a class="reference external" href="../../test/preprocessor.cpp">preprocessor.cpp</a> test program demonstrates proper usage of this macro.</p>
|
|
<p><strong>Macro parameters:</strong></p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">result</tt> is the parenthesized return type of the function.</li>
|
|
<li><tt class="docutils literal">name</tt> is the base name of the function; it determines the name of the
|
|
generated forwarding functions. <tt class="docutils literal">name</tt> may be qualified by the
|
|
<tt class="docutils literal">static</tt> keyword to declare the member function and its helpers as not
|
|
associated with any object of the enclosing type.</li>
|
|
<li><tt class="docutils literal">tag_namespace</tt> is the namespace in which the keywords used by the
|
|
function resides.</li>
|
|
<li><tt class="docutils literal">arguments</tt> is a <a class="reference external" href="../../../preprocessor/doc/index.html">Boost.Preprocessor</a> <a class="reference external" href="../../../preprocessor/doc/data/sequences.html">sequence</a> of
|
|
<em>argument-specifiers</em>, as defined below.</li>
|
|
</ul>
|
|
<p><strong>Argument specifiers syntax:</strong></p>
|
|
<pre class="literal-block">
|
|
argument-specifiers ::= <em>specifier-group0</em> {<em>specifier-group0</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>specifier</em> {<em>specifier</em>}
|
|
'<strong>)</strong>'
|
|
) | (
|
|
'<strong>(</strong>' '<strong>required</strong>'
|
|
<em>specifier</em> {<em>specifier</em>}
|
|
'<strong>)</strong>'
|
|
)
|
|
|
|
specifier ::=
|
|
'<strong>(</strong>' <em>argument-name</em> '<strong>,</strong>' <em>restriction</em> ')'
|
|
|
|
restriction ::=
|
|
( '<strong>*</strong>' '<strong>(</strong>' <em>mfc</em> '<strong>)</strong>' ) |
|
|
( '<strong>(</strong>' <em>type-name</em> '<strong>)</strong>' ) |
|
|
'<strong>*</strong>'
|
|
</pre>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal"><span class="pre">argument-name</span></tt> is any valid C++ identifier.</li>
|
|
<li><tt class="docutils literal">mfc</tt> is an <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary Metafunction Class</a> whose first argument will
|
|
be the type of the corresponding <tt class="docutils literal"><span class="pre">argument-name</span></tt>, whose second argument
|
|
will be the entire <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>, and whose return type is a <a class="reference external" href="../../../mpl/doc/refmanual/integral-constant.html">Boolean
|
|
Integral Constant</a>; however, user code <em>cannot</em> compute <tt class="docutils literal">mfc</tt> in terms
|
|
of <tt class="docutils literal"><span class="pre">previous-name</span> ## _type</tt>.</li>
|
|
<li><tt class="docutils literal"><span class="pre">type-name</span></tt> is either the name of a <strong>target type</strong> or an <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary
|
|
Metafunction Class</a> whose first argument will be the type of the
|
|
corresponding <tt class="docutils literal"><span class="pre">argument-name</span></tt>, whose second argument will be the entire
|
|
<a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>, and whose return type is the <strong>target type</strong>.</li>
|
|
</ul>
|
|
<p>Note that <em>specifier</em> does not include <em>default-value</em>. It is up to the
|
|
function body to determine the default value of all optional arguments.</p>
|
|
<p><strong>Approximate expansion:</strong></p>
|
|
<p>Where:</p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">n</tt> denotes the <em>minimum</em> arity, as determined from <tt class="docutils literal">arguments</tt>.</li>
|
|
<li><tt class="docutils literal">m</tt> denotes the <em>maximum</em> arity, as determined from <tt class="docutils literal">arguments</tt>.</li>
|
|
</ul>
|
|
<pre class="literal-block">
|
|
// If <strong>result</strong> is a template instantiation of <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if_c</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if_c</a>, or
|
|
// <a class="reference external" href="http://en.cppreference.com/w/cpp/types/enable_if">std::enable_if</a>:
|
|
template <typename Args>
|
|
using boost_param_result_ ## __LINE__ ## <strong>name</strong> = <strong>result</strong>;
|
|
|
|
// If <strong>result</strong> is a simple return type:
|
|
template <typename Args>
|
|
struct boost_param_result_ ## __LINE__ ## <strong>name</strong>
|
|
{
|
|
typedef <strong>result</strong> type;
|
|
};
|
|
|
|
struct boost_param_params_ ## __LINE__ ## <strong>name</strong>
|
|
: <a class="reference internal" href="#parameters"><tt class="docutils literal">parameters</tt></a><
|
|
<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 <typename A0, …, typename A ## <strong>n</strong>>
|
|
<strong>result</strong> <strong>name</strong>(
|
|
A0&& a0, …, A ## <strong>n</strong>&& a ## <strong>n</strong>
|
|
, typename boost_param_parameters_ ## __LINE__ ## <strong>name</strong>
|
|
::match<A0, …, A ## <strong>n</strong>>::type
|
|
= boost_param_parameters_ ## __LINE__ ## <strong>name</strong>()
|
|
)
|
|
{
|
|
return this->boost_param_impl ## <strong>name</strong>(
|
|
boost_param_parameters_ ## __LINE__ ## <strong>name</strong>()(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A0>(a0)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>n</strong>>(a ## <strong>n</strong>)
|
|
)
|
|
);
|
|
}
|
|
|
|
<span class="vellipsis">⋮</span>
|
|
|
|
template <typename A0, …, typename A ## <strong>m</strong>>
|
|
<strong>result</strong> <strong>name</strong>(
|
|
A0&& a0, …, A ## <strong>m</strong>&& a ## <strong>m</strong>
|
|
, typename boost_param_parameters_ ## __LINE__ ## <strong>name</strong>
|
|
::match<A0, …, A ## <strong>m</strong>>::type
|
|
= boost_param_parameters_ ## __LINE__ ## <strong>name</strong>()
|
|
)
|
|
{
|
|
return this->boost_param_impl ## <strong>name</strong>(
|
|
boost_param_parameters_ ## __LINE__ ## <strong>name</strong>()(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A0>(a0)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>m</strong>>(a ## <strong>m</strong>)
|
|
)
|
|
);
|
|
}
|
|
|
|
template <typename Args>
|
|
typename boost_param_result_ ## __LINE__ ## <strong>name</strong><Args>::type
|
|
boost_param_impl ## <strong>name</strong>(Args const& args)
|
|
</pre>
|
|
<p>Only the <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> type <tt class="docutils literal">Args</tt> and its object instance <tt class="docutils literal">args</tt> are
|
|
available for use within the function body.</p>
|
|
</div>
|
|
<div class="section" id="boost-parameter-basic-const-member-function-result-name-tag-ns-args">
|
|
<span id="boost-parameter-basic-const-member-function"></span><h2><a class="toc-backref" href="#id65">7.9 <tt class="docutils literal">BOOST_PARAMETER_BASIC_CONST_MEMBER_FUNCTION(result, name, tag_ns, args)</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>
|
|
<p>Generates a member function that can take in positional arguments, composed
|
|
arguments, named arguments, and deduced 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">Example usage:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>The return type of each of the following function templates falls under a
|
|
different value category.</p>
|
|
<pre class="literal-block">
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> rvalue_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const rvalue_const_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>& lvalue_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> lset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return lset;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const& lvalue_const_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const clset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return clset;
|
|
}
|
|
</pre>
|
|
<p>The <tt class="docutils literal"><span class="pre">U::evaluate_category</span></tt> static member function template has a simple job:
|
|
to return the correct value category when passed in an object returned by one
|
|
of the functions defined above. Assume that
|
|
<a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> is defined.</p>
|
|
<pre class="literal-block">
|
|
enum invoked
|
|
{
|
|
passed_by_lvalue_reference_to_const
|
|
, passed_by_lvalue_reference
|
|
, passed_by_rvalue_reference_to_const
|
|
, passed_by_rvalue_reference
|
|
};
|
|
|
|
struct U
|
|
{
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&)
|
|
{
|
|
return passed_by_lvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&)
|
|
{
|
|
return passed_by_lvalue_reference;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&&)
|
|
{
|
|
return passed_by_rvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&&)
|
|
{
|
|
return passed_by_rvalue_reference;
|
|
}
|
|
};
|
|
</pre>
|
|
<p>Define the named parameters that will comprise the argument specification that
|
|
this macro will use. Ensure that all their tag types are in the same
|
|
namespace, which is <tt class="docutils literal">kw</tt> in this case. The identifiers with leading
|
|
underscores can be passed to the bracket operator of <tt class="docutils literal">args</tt> to extract the
|
|
same argument to which the corresponding named parameter (without underscores)
|
|
is bound, as will be shown later.</p>
|
|
<pre class="literal-block">
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lrc, kw) in(lrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lr, kw) in_out(lr))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rrc, kw) in(rrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rr, kw) consume(rr))
|
|
</pre>
|
|
<p>Use the macro as a substitute for a normal <tt class="docutils literal">const</tt> member function
|
|
header. Enclose the return type <tt class="docutils literal">bool</tt> in parentheses. For each parameter,
|
|
also enclose the expected value type in parentheses. Since the value types
|
|
are mutually exclusive, you can wrap the parameters in a <tt class="docutils literal">(deduced …)</tt>
|
|
clause. Otherwise, just as with a normal function, the order in which you
|
|
specify the parameters determines their position. However, unlike a normal
|
|
function, default values must be specified within the function body. Also
|
|
within the function body, you must pass the matching identifier with the
|
|
leading underscore to the bracket operator of <tt class="docutils literal">args</tt> to extract the
|
|
corresponding argument, but at least this doesn't require <tt class="docutils literal"><span class="pre">std::forward</span></tt> to
|
|
preserve value categories.</p>
|
|
<pre class="literal-block">
|
|
struct B
|
|
{
|
|
B()
|
|
{
|
|
}
|
|
|
|
BOOST_PARAMETER_BASIC_CONST_MEMBER_FUNCTION((bool), evaluate, kw,
|
|
(deduced
|
|
(required
|
|
(lrc, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><1>))
|
|
(lr, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><2>))
|
|
)
|
|
(optional
|
|
(rrc, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><3>))
|
|
(rr, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><4>))
|
|
)
|
|
)
|
|
)
|
|
{
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference_to_const
|
|
, U::evaluate_category<0>(args[_lrc])
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference
|
|
, U::evaluate_category<1>(args[_lr])
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference_to_const
|
|
, U::evaluate_category<2>(
|
|
args[_rrc0 | rvalue_const_bitset<2>()]
|
|
)
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference
|
|
, U::evaluate_category<3>(
|
|
args[_rr0 | rvalue_bitset<3>()]
|
|
)
|
|
);
|
|
|
|
return true;
|
|
}
|
|
};
|
|
</pre>
|
|
<p>The following function calls are legal.</p>
|
|
<pre class="literal-block">
|
|
B const b = B();
|
|
b.evaluate( // positional arguments
|
|
lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
, rvalue_const_bitset<2>()
|
|
, rvalue_bitset<3>()
|
|
);
|
|
b.evaluate( // positional arguments
|
|
lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
);
|
|
b.evaluate(( // composed arguments
|
|
_rr0 = rvalue_bitset<3>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
, _lr0 = lvalue_bitset<1>()
|
|
, _rrc0 = rvalue_const_bitset<2>()
|
|
));
|
|
b.evaluate( // named arguments
|
|
_rr0 = rvalue_bitset<3>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
, _lr0 = lvalue_bitset<1>()
|
|
, _rrc0 = rvalue_const_bitset<2>()
|
|
);
|
|
b.evaluate( // named arguments
|
|
_lr0 = lvalue_bitset<1>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
);
|
|
</pre>
|
|
<p>Because the parameters were wrapped in a <tt class="docutils literal">(deduced …)</tt> clause, the following
|
|
function calls are also legal.</p>
|
|
<pre class="literal-block">
|
|
b.evaluate( // deduced arguments
|
|
rvalue_bitset<3>()
|
|
, lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
, rvalue_const_bitset<2>()
|
|
);
|
|
b.evaluate( // deduced arguments
|
|
lvalue_bitset<1>()
|
|
, lvalue_const_bitset<0>()
|
|
);
|
|
</pre>
|
|
<p>The <a class="reference external" href="../../test/preprocessor.cpp">preprocessor.cpp</a> test program demonstrates proper usage of this macro.</p>
|
|
<p><strong>Macro parameters:</strong></p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">result</tt> is the parenthesized return type of the function.</li>
|
|
<li><tt class="docutils literal">name</tt> is the base name of the function; it determines the name of the
|
|
generated forwarding functions.</li>
|
|
<li><tt class="docutils literal">tag_namespace</tt> is the namespace in which the keywords used by the
|
|
function resides.</li>
|
|
<li><tt class="docutils literal">arguments</tt> is a <a class="reference external" href="../../../preprocessor/doc/index.html">Boost.Preprocessor</a> <a class="reference external" href="../../../preprocessor/doc/data/sequences.html">sequence</a> of
|
|
<em>argument-specifiers</em>, as defined below.</li>
|
|
</ul>
|
|
<p><strong>Argument specifiers syntax:</strong></p>
|
|
<pre class="literal-block">
|
|
argument-specifiers ::= <em>specifier-group0</em> {<em>specifier-group0</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>specifier</em> {<em>specifier</em>}
|
|
'<strong>)</strong>'
|
|
) | (
|
|
'<strong>(</strong>' '<strong>required</strong>'
|
|
<em>specifier</em> {<em>specifier</em>}
|
|
'<strong>)</strong>'
|
|
)
|
|
|
|
specifier ::=
|
|
'<strong>(</strong>' <em>argument-name</em> '<strong>,</strong>' <em>restriction</em> ')'
|
|
|
|
restriction ::=
|
|
( '<strong>*</strong>' '<strong>(</strong>' <em>mfc</em> '<strong>)</strong>' ) |
|
|
( '<strong>(</strong>' <em>type-name</em> '<strong>)</strong>' ) |
|
|
'<strong>*</strong>'
|
|
</pre>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal"><span class="pre">argument-name</span></tt> is any valid C++ identifier.</li>
|
|
<li><tt class="docutils literal">mfc</tt> is an <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary Metafunction Class</a> whose first argument will
|
|
be the type of the corresponding <tt class="docutils literal"><span class="pre">argument-name</span></tt>, whose second argument
|
|
will be the entire <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>, and whose return type is a <a class="reference external" href="../../../mpl/doc/refmanual/integral-constant.html">Boolean
|
|
Integral Constant</a>; however, user code <em>cannot</em> compute <tt class="docutils literal">mfc</tt> in terms
|
|
of <tt class="docutils literal"><span class="pre">previous-name</span> ## _type</tt>.</li>
|
|
<li><tt class="docutils literal"><span class="pre">type-name</span></tt> is either the name of a <strong>target type</strong> or an <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary
|
|
Metafunction Class</a> whose first argument will be the type of the
|
|
corresponding <tt class="docutils literal"><span class="pre">argument-name</span></tt>, whose second argument will be the entire
|
|
<a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>, and whose return type is the <strong>target type</strong>.</li>
|
|
</ul>
|
|
<p>Note that <em>specifier</em> does not include <em>default-value</em>. It is up to the
|
|
function body to determine the default value of all optional arguments.</p>
|
|
<p><strong>Approximate expansion:</strong></p>
|
|
<p>Where:</p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">n</tt> denotes the <em>minimum</em> arity, as determined from <tt class="docutils literal">arguments</tt>.</li>
|
|
<li><tt class="docutils literal">m</tt> denotes the <em>maximum</em> arity, as determined from <tt class="docutils literal">arguments</tt>.</li>
|
|
</ul>
|
|
<pre class="literal-block">
|
|
// If <strong>result</strong> is a template instantiation of <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if_c</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if_c</a>, or
|
|
// <a class="reference external" href="http://en.cppreference.com/w/cpp/types/enable_if">std::enable_if</a>:
|
|
template <typename Args>
|
|
using boost_param_result_const_ ## __LINE__ ## <strong>name</strong> = <strong>result</strong>;
|
|
|
|
// If <strong>result</strong> is a simple return type:
|
|
template <typename Args>
|
|
struct boost_param_result_const_ ## __LINE__ ## <strong>name</strong>
|
|
{
|
|
typedef <strong>result</strong> type;
|
|
};
|
|
|
|
struct boost_param_params_const_ ## __LINE__ ## <strong>name</strong>
|
|
: <a class="reference internal" href="#parameters"><tt class="docutils literal">parameters</tt></a><
|
|
<em>list of parameter specifications, based on arguments</em>
|
|
>
|
|
{
|
|
};
|
|
|
|
typedef boost_param_params_const_ ## __LINE__ ## <strong>name</strong>
|
|
boost_param_parameters_const_ ## __LINE__ ## <strong>name</strong>;
|
|
|
|
template <typename A0, …, typename A ## <strong>n</strong>>
|
|
<strong>result</strong> <strong>name</strong>(
|
|
A0&& a0, …, A ## <strong>n</strong>&& a ## <strong>n</strong>
|
|
, typename boost_param_parameters_const_ ## __LINE__ ## <strong>name</strong>
|
|
::match<A0, …, A ## <strong>n</strong>>::type
|
|
= boost_param_parameters_const_ ## __LINE__ ## <strong>name</strong>()
|
|
) const
|
|
{
|
|
return this->boost_param_impl_const ## __LINE__ ## <strong>name</strong>(
|
|
boost_param_parameters_const_ ## __LINE__ ## <strong>name</strong>()(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A0>(a0)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>n</strong>>(a ## <strong>n</strong>)
|
|
)
|
|
);
|
|
}
|
|
|
|
<span class="vellipsis">⋮</span>
|
|
|
|
template <typename A0, …, typename A ## <strong>m</strong>>
|
|
<strong>result</strong> <strong>name</strong>(
|
|
A0&& a0, …, A ## <strong>m</strong>&& a ## <strong>m</strong>
|
|
, typename boost_param_parameters_const_ ## __LINE__ ## <strong>name</strong>
|
|
::match<A0, …, A ## <strong>m</strong>>::type
|
|
= boost_param_parameters_const_ ## __LINE__ ## <strong>name</strong>()
|
|
) const
|
|
{
|
|
return this->boost_param_impl_const ## __LINE__ ## <strong>name</strong>(
|
|
boost_param_parameters_const_ ## __LINE__ ## <strong>name</strong>()(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A0>(a0)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>m</strong>>(a ## <strong>m</strong>)
|
|
)
|
|
);
|
|
}
|
|
|
|
template <typename Args>
|
|
typename boost_param_result_const_ ## __LINE__ ## <strong>name</strong><Args>::type
|
|
boost_param_impl_const ## __LINE__ ## <strong>name</strong>(Args const& args) const
|
|
</pre>
|
|
<p>Only the <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> type <tt class="docutils literal">Args</tt> and its object instance <tt class="docutils literal">args</tt> are
|
|
available for use within the function body.</p>
|
|
</div>
|
|
<div class="section" id="boost-parameter-basic-function-call-operator-result-tag-ns-arguments">
|
|
<span id="boost-parameter-basic-function-call-operator"></span><h2><a class="toc-backref" href="#id66">7.10 <tt class="docutils literal">BOOST_PARAMETER_BASIC_FUNCTION_CALL_OPERATOR(result, tag_ns, arguments)</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>
|
|
<p>Generates a function call operator that can take in positional arguments,
|
|
composed arguments, named arguments, and deduced 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">Example usage:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>Define the named parameters that will comprise the argument specification that
|
|
this macro will use. Ensure that all their tag types are in the same
|
|
namespace, which is <tt class="docutils literal">tag</tt> by default.</p>
|
|
<pre class="literal-block">
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>(y)
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>(z)
|
|
</pre>
|
|
<p>Use the macro as a substitute for a normal function call operator
|
|
header. Enclose the return type in parentheses. For each parameter, also
|
|
enclose the expected value type in parentheses. Since the value types are
|
|
mutually exclusive, you can wrap the parameters in a <tt class="docutils literal">(deduced …)</tt>
|
|
clause. This is especially useful when implementing multiple
|
|
Boost.Parameter-enabled function call operator overloads.</p>
|
|
<pre class="literal-block">
|
|
class char_reader
|
|
{
|
|
int index;
|
|
char const* key;
|
|
|
|
public:
|
|
explicit char_reader(char const* k) : index(0), key(k)
|
|
{
|
|
}
|
|
|
|
BOOST_PARAMETER_BASIC_FUNCTION_CALL_OPERATOR((void), tag,
|
|
(deduced
|
|
(required
|
|
(y, (int))
|
|
(z, (char const*))
|
|
)
|
|
)
|
|
)
|
|
{
|
|
this->index = args[_y];
|
|
this->key = args[_z];
|
|
}
|
|
|
|
<a class="reference internal" href="#boost-parameter-basic-const-function-call-operator"><tt class="docutils literal">BOOST_PARAMETER_BASIC_CONST_FUNCTION_CALL_OPERATOR</tt></a>((char), tag,
|
|
(deduced
|
|
(required
|
|
(y, (bool))
|
|
(z, (<a class="reference external" href="http://en.cppreference.com/w/cpp/container/map">std::map</a><char const*, <a class="reference external" href="http://en.cppreference.com/w/cpp/string/basic_string">std::string</a>>))
|
|
)
|
|
)
|
|
)
|
|
{
|
|
return args[_y] ? (
|
|
(args[_z].find(this->key)->second)[this->index]
|
|
) : this->key[this->index];
|
|
}
|
|
};
|
|
</pre>
|
|
<p>As with regular argument-dependent lookup, the value types of the arguments
|
|
passed in determine which function call operator overload gets invoked.</p>
|
|
<pre class="literal-block">
|
|
char const* keys[] = {"foo", "bar", "baz"};
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/container/map">std::map</a><char const*, <a class="reference external" href="http://en.cppreference.com/w/cpp/string/basic_string">std::string</a>> k2s;
|
|
k2s[keys[0]] = <a class="reference external" href="http://en.cppreference.com/w/cpp/string/basic_string">std::string</a>("qux");
|
|
k2s[keys[1]] = <a class="reference external" href="http://en.cppreference.com/w/cpp/string/basic_string">std::string</a>("wmb");
|
|
k2s[keys[2]] = <a class="reference external" href="http://en.cppreference.com/w/cpp/string/basic_string">std::string</a>("zxc");
|
|
char_reader r(keys[0]);
|
|
|
|
// positional arguments
|
|
BOOST_TEST_EQ('q', (r(true, k2s)));
|
|
BOOST_TEST_EQ('f', (r(false, k2s)));
|
|
|
|
// named arguments
|
|
r(_z = keys[1], _y = 1);
|
|
BOOST_TEST_EQ('m', (r(_z = k2s, _y = true)));
|
|
BOOST_TEST_EQ('a', (r(_z = k2s, _y = false)));
|
|
|
|
// deduced arguments
|
|
r(keys[2], 2);
|
|
BOOST_TEST_EQ('c', (r(k2s, true)));
|
|
BOOST_TEST_EQ('z', (r(k2s, false)));
|
|
</pre>
|
|
<p>The <a class="reference external" href="../../test/preprocessor.cpp">preprocessor.cpp</a> test program demonstrates proper usage of this macro.</p>
|
|
<p><strong>Macro parameters:</strong></p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">result</tt> is the parenthesized return type of the function call operator.</li>
|
|
<li><tt class="docutils literal">tag_namespace</tt> is the namespace in which the keywords used by the
|
|
function call operator resides.</li>
|
|
<li><tt class="docutils literal">arguments</tt> is a <a class="reference external" href="../../../preprocessor/doc/index.html">Boost.Preprocessor</a> <a class="reference external" href="../../../preprocessor/doc/data/sequences.html">sequence</a> of
|
|
<em>argument-specifiers</em>, as defined below.</li>
|
|
</ul>
|
|
<p><strong>Argument specifiers syntax:</strong></p>
|
|
<pre class="literal-block">
|
|
argument-specifiers ::= <em>specifier-group0</em> {<em>specifier-group0</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>specifier</em> {<em>specifier</em>}
|
|
'<strong>)</strong>'
|
|
) | (
|
|
'<strong>(</strong>' '<strong>required</strong>'
|
|
<em>specifier</em> {<em>specifier</em>}
|
|
'<strong>)</strong>'
|
|
)
|
|
|
|
specifier ::=
|
|
'<strong>(</strong>' <em>argument-name</em> '<strong>,</strong>' <em>restriction</em> ')'
|
|
|
|
restriction ::=
|
|
( '<strong>*</strong>' '<strong>(</strong>' <em>mfc</em> '<strong>)</strong>' ) |
|
|
( '<strong>(</strong>' <em>type-name</em> '<strong>)</strong>' ) |
|
|
'<strong>*</strong>'
|
|
</pre>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal"><span class="pre">argument-name</span></tt> is any valid C++ identifier.</li>
|
|
<li><tt class="docutils literal">mfc</tt> is an <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary Metafunction Class</a> whose first argument will
|
|
be the type of the corresponding <tt class="docutils literal"><span class="pre">argument-name</span></tt>, whose second argument
|
|
will be the entire <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>, and whose return type is a <a class="reference external" href="../../../mpl/doc/refmanual/integral-constant.html">Boolean
|
|
Integral Constant</a>; however, user code <em>cannot</em> compute <tt class="docutils literal">mfc</tt> in terms
|
|
of <tt class="docutils literal"><span class="pre">previous-name</span> ## _type</tt>.</li>
|
|
<li><tt class="docutils literal"><span class="pre">type-name</span></tt> is either the name of a <strong>target type</strong> or an <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary
|
|
Metafunction Class</a> whose first argument will be the type of the
|
|
corresponding <tt class="docutils literal"><span class="pre">argument-name</span></tt>, whose second argument will be the entire
|
|
<a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>, and whose return type is the <strong>target type</strong>.</li>
|
|
</ul>
|
|
<p>Note that <em>specifier</em> does not include <em>default-value</em>. It is up to the
|
|
function body to determine the default value of all optional arguments.</p>
|
|
<p><strong>Approximate expansion:</strong></p>
|
|
<p>Where:</p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">n</tt> denotes the <em>minimum</em> arity, as determined from <tt class="docutils literal">arguments</tt>.</li>
|
|
<li><tt class="docutils literal">m</tt> denotes the <em>maximum</em> arity, as determined from <tt class="docutils literal">arguments</tt>.</li>
|
|
</ul>
|
|
<pre class="literal-block">
|
|
// If <strong>result</strong> is a template instantiation of <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if_c</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if_c</a>, or
|
|
// <a class="reference external" href="http://en.cppreference.com/w/cpp/types/enable_if">std::enable_if</a>:
|
|
template <typename Args>
|
|
using boost_param_result_ ## __LINE__ ## operator = <strong>result</strong>;
|
|
|
|
// If <strong>result</strong> is a simple return type:
|
|
template <typename Args>
|
|
struct boost_param_result_ ## __LINE__ ## operator
|
|
{
|
|
typedef <strong>result</strong> type;
|
|
};
|
|
|
|
struct boost_param_params_ ## __LINE__ ## operator
|
|
: <a class="reference internal" href="#parameters"><tt class="docutils literal">parameters</tt></a><
|
|
<em>list of parameter specifications, based on arguments</em>
|
|
>
|
|
{
|
|
};
|
|
|
|
typedef boost_param_params_ ## __LINE__ ## operator
|
|
boost_param_parameters_ ## __LINE__ ## operator;
|
|
|
|
template <typename A0, …, typename A ## <strong>n</strong>>
|
|
<strong>result</strong> operator()(
|
|
A0&& a0, …, A ## <strong>n</strong>&& a ## <strong>n</strong>
|
|
, typename boost_param_parameters_ ## __LINE__ ## operator::match<
|
|
A0, …, A ## <strong>n</strong>
|
|
>::type = boost_param_parameters_ ## __LINE__ ## operator()
|
|
)
|
|
{
|
|
return this->boost_param_impl ## __LINE__ ## operator(
|
|
boost_param_parameters_ ## __LINE__ ## operator()(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A0>(a0)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>n</strong>>(a ## <strong>n</strong>)
|
|
)
|
|
);
|
|
}
|
|
|
|
<span class="vellipsis">⋮</span>
|
|
|
|
template <typename A0, …, typename A ## <strong>m</strong>>
|
|
<strong>result</strong> operator()(
|
|
A0&& a0, …, A ## <strong>m</strong>&& a ## <strong>m</strong>
|
|
, typename boost_param_parameters_ ## __LINE__ ## operator::match<
|
|
A0, …, A ## <strong>m</strong>
|
|
>::type = boost_param_parameters_ ## __LINE__ ## operator()
|
|
)
|
|
{
|
|
return this->boost_param_impl ## __LINE__ ## operator(
|
|
boost_param_parameters_ ## __LINE__ ## operator()(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A0>(a0)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>m</strong>>(a ## <strong>m</strong>)
|
|
)
|
|
);
|
|
}
|
|
|
|
template <typename Args>
|
|
typename boost_param_result_ ## __LINE__ ## operator<Args>::type
|
|
boost_param_impl ## __LINE__ ## operator(Args const& args)
|
|
</pre>
|
|
<p>Only the <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> type <tt class="docutils literal">Args</tt> and its object instance <tt class="docutils literal">args</tt> are
|
|
available for use within the function call operator body.</p>
|
|
</div>
|
|
<div class="section" id="boost-parameter-basic-const-function-call-operator-result-tag-ns-args">
|
|
<span id="boost-parameter-basic-const-function-call-operator"></span><h2><a class="toc-backref" href="#id67">7.11 <tt class="docutils literal">BOOST_PARAMETER_BASIC_CONST_FUNCTION_CALL_OPERATOR(result, tag_ns, args)</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>
|
|
<p>Generates a function call operator that can take in positional arguments,
|
|
composed arguments, named arguments, and deduced 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">Example usage:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>The return type of each of the following function templates falls under a
|
|
different value category.</p>
|
|
<pre class="literal-block">
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> rvalue_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const rvalue_const_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>& lvalue_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> lset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return lset;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const& lvalue_const_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const clset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return clset;
|
|
}
|
|
</pre>
|
|
<p>The <tt class="docutils literal"><span class="pre">U::evaluate_category</span></tt> static member function template has a simple job:
|
|
to return the correct value category when passed in an object returned by one
|
|
of the functions defined above. Assume that
|
|
<a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> is defined.</p>
|
|
<pre class="literal-block">
|
|
enum invoked
|
|
{
|
|
passed_by_lvalue_reference_to_const
|
|
, passed_by_lvalue_reference
|
|
, passed_by_rvalue_reference_to_const
|
|
, passed_by_rvalue_reference
|
|
};
|
|
|
|
struct U
|
|
{
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&)
|
|
{
|
|
return passed_by_lvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&)
|
|
{
|
|
return passed_by_lvalue_reference;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&&)
|
|
{
|
|
return passed_by_rvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&&)
|
|
{
|
|
return passed_by_rvalue_reference;
|
|
}
|
|
};
|
|
</pre>
|
|
<p>Define the named parameters that will comprise the argument specification that
|
|
this macro will use. Ensure that all their tag types are in the same
|
|
namespace, which is <tt class="docutils literal">kw</tt> in this case. The identifiers with leading
|
|
underscores can be passed to the bracket operator of <tt class="docutils literal">args</tt> to extract the
|
|
same argument to which the corresponding named parameter (without underscores)
|
|
is bound, as will be shown later.</p>
|
|
<pre class="literal-block">
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lrc, kw) in(lrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lr, kw) in_out(lr))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rrc, kw) in(rrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rr, kw) consume(rr))
|
|
</pre>
|
|
<p>Use the macro as a substitute for a normal <tt class="docutils literal">const</tt> function call operator
|
|
header. Enclose the return type <tt class="docutils literal">bool</tt> in parentheses. For each parameter,
|
|
also enclose the expected value type in parentheses. Since the value types
|
|
are mutually exclusive, you can wrap the parameters in a <tt class="docutils literal">(deduced …)</tt>
|
|
clause. Otherwise, just as with a normal function, the order in which you
|
|
specify the parameters determines their position. However, unlike a normal
|
|
function, default values must be specified within the function body. Also
|
|
within the function body, you must pass the matching identifier with the
|
|
leading underscore to the bracket operator of <tt class="docutils literal">args</tt> to extract the
|
|
corresponding argument, but at least this doesn't require <tt class="docutils literal"><span class="pre">std::forward</span></tt> to
|
|
preserve value categories.</p>
|
|
<pre class="literal-block">
|
|
struct B
|
|
{
|
|
B()
|
|
{
|
|
}
|
|
|
|
BOOST_PARAMETER_BASIC_CONST_FUNCTION_CALL_OPERATOR((bool), kw,
|
|
(deduced
|
|
(required
|
|
(lrc, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><1>))
|
|
(lr, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><2>))
|
|
)
|
|
(optional
|
|
(rrc, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><3>))
|
|
(rr, (<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><4>))
|
|
)
|
|
)
|
|
)
|
|
{
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference_to_const
|
|
, U::evaluate_category<0>(args[_lrc])
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference
|
|
, U::evaluate_category<1>(args[_lr])
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference_to_const
|
|
, U::evaluate_category<2>(
|
|
args[_rrc0 | rvalue_const_bitset<2>()]
|
|
)
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference
|
|
, U::evaluate_category<3>(
|
|
args[_rr0 | rvalue_bitset<3>()]
|
|
)
|
|
);
|
|
|
|
return true;
|
|
}
|
|
};
|
|
</pre>
|
|
<p>The following function calls are legal.</p>
|
|
<pre class="literal-block">
|
|
B const b = B();
|
|
b( // positional arguments
|
|
lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
, rvalue_const_bitset<2>()
|
|
, rvalue_bitset<3>()
|
|
);
|
|
b( // positional arguments
|
|
lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
);
|
|
b(( // composed arguments
|
|
_rr0 = rvalue_bitset<3>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
, _lr0 = lvalue_bitset<1>()
|
|
, _rrc0 = rvalue_const_bitset<2>()
|
|
));
|
|
b( // named arguments
|
|
_rr0 = rvalue_bitset<3>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
, _lr0 = lvalue_bitset<1>()
|
|
, _rrc0 = rvalue_const_bitset<2>()
|
|
);
|
|
b( // named arguments
|
|
_lr0 = lvalue_bitset<1>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
);
|
|
</pre>
|
|
<p>Because the parameters were wrapped in a <tt class="docutils literal">(deduced …)</tt> clause, the following
|
|
function calls are also legal.</p>
|
|
<pre class="literal-block">
|
|
b( // deduced arguments
|
|
rvalue_bitset<3>()
|
|
, lvalue_const_bitset<0>()
|
|
, lvalue_bitset<1>()
|
|
, rvalue_const_bitset<2>()
|
|
);
|
|
b( // deduced arguments
|
|
lvalue_bitset<1>()
|
|
, lvalue_const_bitset<0>()
|
|
);
|
|
</pre>
|
|
<p>The <a class="reference external" href="../../test/preprocessor.cpp">preprocessor.cpp</a> test program demonstrates proper usage of this macro.</p>
|
|
<p><strong>Macro parameters:</strong></p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">result</tt> is the parenthesized return type of the function call operator.</li>
|
|
<li><tt class="docutils literal">tag_namespace</tt> is the namespace in which the keywords used by the
|
|
function call operator resides.</li>
|
|
<li><tt class="docutils literal">arguments</tt> is a <a class="reference external" href="../../../preprocessor/doc/index.html">Boost.Preprocessor</a> <a class="reference external" href="../../../preprocessor/doc/data/sequences.html">sequence</a> of
|
|
<em>argument-specifiers</em>, as defined below.</li>
|
|
</ul>
|
|
<p><strong>Argument specifiers syntax:</strong></p>
|
|
<pre class="literal-block">
|
|
argument-specifiers ::= <em>specifier-group0</em> {<em>specifier-group0</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>specifier</em> {<em>specifier</em>}
|
|
'<strong>)</strong>'
|
|
) | (
|
|
'<strong>(</strong>' '<strong>required</strong>'
|
|
<em>specifier</em> {<em>specifier</em>}
|
|
'<strong>)</strong>'
|
|
)
|
|
|
|
specifier ::=
|
|
'<strong>(</strong>' <em>argument-name</em> '<strong>,</strong>' <em>restriction</em> ')'
|
|
|
|
restriction ::=
|
|
( '<strong>*</strong>' '<strong>(</strong>' <em>mfc</em> '<strong>)</strong>' ) |
|
|
( '<strong>(</strong>' <em>type-name</em> '<strong>)</strong>' ) |
|
|
'<strong>*</strong>'
|
|
</pre>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal"><span class="pre">argument-name</span></tt> is any valid C++ identifier.</li>
|
|
<li><tt class="docutils literal">mfc</tt> is an <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary Metafunction Class</a> whose first argument will
|
|
be the type of the corresponding <tt class="docutils literal"><span class="pre">argument-name</span></tt>, whose second argument
|
|
will be the entire <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>, and whose return type is a <a class="reference external" href="../../../mpl/doc/refmanual/integral-constant.html">Boolean
|
|
Integral Constant</a>; however, user code <em>cannot</em> compute <tt class="docutils literal">mfc</tt> in terms
|
|
of <tt class="docutils literal"><span class="pre">previous-name</span> ## _type</tt>.</li>
|
|
<li><tt class="docutils literal"><span class="pre">type-name</span></tt> is either the name of a <strong>target type</strong> or an <a class="reference external" href="../../../mpl/doc/refmanual/metafunction-class.html">MPL Binary
|
|
Metafunction Class</a> whose first argument will be the type of the
|
|
corresponding <tt class="docutils literal"><span class="pre">argument-name</span></tt>, whose second argument will be the entire
|
|
<a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>, and whose return type is the <strong>target type</strong>.</li>
|
|
</ul>
|
|
<p>Note that <em>specifier</em> does not include <em>default-value</em>. It is up to the
|
|
function body to determine the default value of all optional arguments.</p>
|
|
<p><strong>Approximate expansion:</strong></p>
|
|
<p>Where:</p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">n</tt> denotes the <em>minimum</em> arity, as determined from <tt class="docutils literal">arguments</tt>.</li>
|
|
<li><tt class="docutils literal">m</tt> denotes the <em>maximum</em> arity, as determined from <tt class="docutils literal">arguments</tt>.</li>
|
|
</ul>
|
|
<pre class="literal-block">
|
|
// If <strong>result</strong> is a template instantiation of <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if_c</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if_c</a>, or
|
|
// <a class="reference external" href="http://en.cppreference.com/w/cpp/types/enable_if">std::enable_if</a>:
|
|
template <typename Args>
|
|
using boost_param_result_const_ ## __LINE__ ## operator = <strong>result</strong>;
|
|
|
|
// If <strong>result</strong> is a simple return type:
|
|
template <typename Args>
|
|
struct boost_param_result_const_ ## __LINE__ ## operator
|
|
{
|
|
typedef <strong>result</strong> type;
|
|
};
|
|
|
|
struct boost_param_params_const_ ## __LINE__ ## operator
|
|
: <a class="reference internal" href="#parameters"><tt class="docutils literal">parameters</tt></a><
|
|
<em>list of parameter specifications, based on arguments</em>
|
|
>
|
|
{
|
|
};
|
|
|
|
typedef boost_param_params_const_ ## __LINE__ ## operator
|
|
boost_param_parameters_const_ ## __LINE__ ## operator;
|
|
|
|
template <typename A0, …, typename A ## <strong>n</strong>>
|
|
<strong>result</strong> operator()(
|
|
A0&& a0, …, A ## <strong>n</strong>&& a ## <strong>n</strong>
|
|
, typename boost_param_parameters_const_ ## __LINE__ ## operator
|
|
::match<A0, …, A ## <strong>n</strong>>::type
|
|
= boost_param_parameters_const_ ## __LINE__ ## operator()
|
|
) const
|
|
{
|
|
return this->boost_param_impl_const ## __LINE__ ## operator(
|
|
boost_param_parameters_const_ ## __LINE__ ## operator()(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A0>(a0)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>n</strong>>(a ## <strong>n</strong>)
|
|
)
|
|
);
|
|
}
|
|
|
|
<span class="vellipsis">⋮</span>
|
|
|
|
template <typename A0, …, typename A ## <strong>m</strong>>
|
|
<strong>result</strong> operator()(
|
|
A0&& a0, …, A ## <strong>m</strong>&& a ## <strong>m</strong>
|
|
, typename boost_param_parameters_const_ ## __LINE__ ## operator
|
|
::match<A0, …, A ## <strong>m</strong>>::type
|
|
= boost_param_parameters_const_ ## __LINE__ ## operator()
|
|
) const
|
|
{
|
|
return this->boost_param_impl_const ## __LINE__ ## operator(
|
|
boost_param_parameters_const_ ## __LINE__ ## operator()(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A0>(a0)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>m</strong>>(a ## <strong>m</strong>)
|
|
)
|
|
);
|
|
}
|
|
|
|
template <typename Args>
|
|
typename boost_param_result_const_ ## __LINE__ ## operator<Args>::type
|
|
boost_param_impl_const ## __LINE__ ## operator(Args const& args) const
|
|
</pre>
|
|
<p>Only the <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> type <tt class="docutils literal">Args</tt> and its object instance <tt class="docutils literal">args</tt> are
|
|
available for use within the function call operator body.</p>
|
|
</div>
|
|
<div class="section" id="boost-parameter-no-spec-function-result-name">
|
|
<span id="boost-parameter-no-spec-function"></span><h2><a class="toc-backref" href="#id68">7.12 <tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_FUNCTION(result, name)</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_no_spec.hpp">boost/parameter/preprocessor_no_spec.hpp</a></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>Generates a function that can take in named 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">Example usage:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>The return type of each of the following function templates falls under a
|
|
different value category.</p>
|
|
<pre class="literal-block">
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> rvalue_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const rvalue_const_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>& lvalue_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> lset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return lset;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const& lvalue_const_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const clset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return clset;
|
|
}
|
|
</pre>
|
|
<p>The <tt class="docutils literal"><span class="pre">U::evaluate_category</span></tt> static member function template has a simple job:
|
|
to return the correct value category when passed in an object returned by one
|
|
of the functions defined above. Assume that
|
|
<a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> is defined.</p>
|
|
<pre class="literal-block">
|
|
enum invoked
|
|
{
|
|
passed_by_lvalue_reference_to_const
|
|
, passed_by_lvalue_reference
|
|
, passed_by_rvalue_reference_to_const
|
|
, passed_by_rvalue_reference
|
|
};
|
|
|
|
struct U
|
|
{
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&)
|
|
{
|
|
return passed_by_lvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&)
|
|
{
|
|
return passed_by_lvalue_reference;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&&)
|
|
{
|
|
return passed_by_rvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&&)
|
|
{
|
|
return passed_by_rvalue_reference;
|
|
}
|
|
};
|
|
</pre>
|
|
<p>Named parameters are required when invoking the function; however, none of
|
|
their tags need to be in the same namespace.</p>
|
|
<pre class="literal-block">
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lrc, kw0) in(lrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lr, kw1) in_out(lr))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rrc, kw2) in(rrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rr, kw3) consume(rr))
|
|
</pre>
|
|
<p>Use the macro as a substitute for a variadic function header. Enclose the
|
|
return type <tt class="docutils literal">bool</tt> in parentheses.</p>
|
|
<pre class="literal-block">
|
|
BOOST_PARAMETER_NO_SPEC_FUNCTION((bool), evaluate)
|
|
{
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference_to_const
|
|
, U::evaluate_category<0>(args[_lrc])
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference
|
|
, U::evaluate_category<1>(args[_lr])
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference_to_const
|
|
, U::evaluate_category<2>(
|
|
args[_rrc | rvalue_const_bitset<2>()]
|
|
)
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference
|
|
, U::evaluate_category<3>(args[_rr | rvalue_bitset<3>()])
|
|
);
|
|
|
|
return true;
|
|
}
|
|
</pre>
|
|
<p>To invoke the function, bind all its arguments to named parameters.</p>
|
|
<pre class="literal-block">
|
|
evaluate(
|
|
_rr0 = rvalue_bitset<3>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
, _lr0 = lvalue_bitset<1>()
|
|
, _rrc0 = rvalue_const_bitset<2>()
|
|
);
|
|
evaluate(
|
|
_lr0 = lvalue_bitset<1>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
);
|
|
</pre>
|
|
<p>The <a class="reference external" href="../../test/preprocessor_eval_cat_no_spec.cpp">preprocessor_eval_cat_no_spec.cpp</a> test program demonstrates proper usage of
|
|
this macro.</p>
|
|
<p><strong>Macro parameters:</strong></p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">result</tt> is the parenthesized return type of the function.</li>
|
|
<li><tt class="docutils literal">name</tt> is the base name of the function; it determines the name of the
|
|
generated implementation function.</li>
|
|
</ul>
|
|
<p><strong>Argument specifiers syntax:</strong></p>
|
|
<p>None.</p>
|
|
<p><strong>Approximate expansion:</strong></p>
|
|
<pre class="literal-block">
|
|
// If <strong>result</strong> is a template instantiation of <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if_c</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if_c</a>, or
|
|
// <a class="reference external" href="http://en.cppreference.com/w/cpp/types/enable_if">std::enable_if</a>:
|
|
template <typename TaggedArg0, typename ...TaggedArgs>
|
|
using boost_param_no_spec_result_ ## __LINE__ ## <strong>name</strong> = <strong>result</strong>;
|
|
|
|
// If <strong>result</strong> is a simple return type:
|
|
template <typename TaggedArg0, typename ...TaggedArgs>
|
|
struct boost_param_no_spec_result_ ## __LINE__ ## <strong>name</strong>
|
|
{
|
|
typedef <strong>result</strong> type;
|
|
};
|
|
|
|
template <typename ResultType, typename Args>
|
|
ResultType
|
|
boost_param_no_spec_impl ## __LINE__ ## <strong>name</strong>(
|
|
(ResultType(*)())
|
|
, Args const& args
|
|
);
|
|
|
|
template <typename TaggedArg0, typename ...TaggedArgs>
|
|
inline typename <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if</a><
|
|
<a class="reference internal" href="#are-tagged-arguments"><tt class="docutils literal">are_tagged_arguments</tt></a><TaggedArg0,TaggedArgs...>
|
|
, boost_param_no_spec_result_ ## __LINE__ ## <strong>name</strong><
|
|
TaggedArg0
|
|
, TaggedArgs...
|
|
>
|
|
>::type
|
|
<strong>name</strong>(TaggedArg0 const& arg0, TaggedArgs const&... args)
|
|
{
|
|
return boost_param_no_spec_impl ## __LINE__ ## <strong>name</strong>(
|
|
static_cast<
|
|
typename
|
|
boost_param_no_spec_result_ ## __LINE__ ## <strong>name</strong><
|
|
TaggedArg0
|
|
, TaggedArgs...
|
|
>::type(*)()
|
|
>(<a class="reference external" href="http://en.cppreference.com/w/cpp/language/nullptr">std::nullptr</a>)
|
|
, <a class="reference internal" href="#compose"><tt class="docutils literal">compose</tt></a>(arg0, args...)
|
|
);
|
|
}
|
|
|
|
template <typename ResultType, typename Args>
|
|
ResultType
|
|
boost_param_no_spec_impl ## __LINE__ ## <strong>name</strong>(
|
|
(ResultType(*)())
|
|
, Args const& args
|
|
)
|
|
</pre>
|
|
<p>Only the <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> type <tt class="docutils literal">Args</tt> and its object instance <tt class="docutils literal">args</tt> are
|
|
available for use within the function body.</p>
|
|
</div>
|
|
<div class="section" id="boost-parameter-no-spec-member-function-result-name">
|
|
<span id="boost-parameter-no-spec-member-function"></span><h2><a class="toc-backref" href="#id69">7.13 <tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_MEMBER_FUNCTION(result, name)</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_no_spec.hpp">boost/parameter/preprocessor_no_spec.hpp</a></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>Generates a member function that can take in named 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">Example usage:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>When designing a front-end class template whose back-end is configurable via
|
|
parameterized inheritance, it can be useful to omit argument specifiers from
|
|
a named-parameter member function so that the delegate member functions of the
|
|
back-end classes can enforce their own specifications.</p>
|
|
<pre class="literal-block">
|
|
template <typename B>
|
|
struct frontend : B
|
|
{
|
|
frontend() : B()
|
|
{
|
|
}
|
|
|
|
BOOST_PARAMETER_NO_SPEC_MEMBER_FUNCTION((void), initialize)
|
|
{
|
|
this->initialize_impl(args);
|
|
}
|
|
};
|
|
</pre>
|
|
<p>Named parameters are required when invoking the member function; however, none
|
|
of their tags need to be in the same namespace.</p>
|
|
<pre class="literal-block">
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>(a0)
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>(a1)
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>(a2)
|
|
</pre>
|
|
<p>For this example, each of the back-end class templates requires its own
|
|
parameter to be present in the argument pack. In practice, such parameters
|
|
should be optional, with default values.</p>
|
|
<pre class="literal-block">
|
|
template <typename T>
|
|
class backend0
|
|
{
|
|
T a0;
|
|
|
|
public:
|
|
backend0() : a0()
|
|
{
|
|
}
|
|
|
|
T const& get_a0() const
|
|
{
|
|
return this->a0;
|
|
}
|
|
|
|
protected:
|
|
template <typename ArgPack>
|
|
void initialize_impl(ArgPack const& args)
|
|
{
|
|
this->a0 = args[_a0];
|
|
}
|
|
};
|
|
|
|
template <typename B, typename T>
|
|
class backend1 : public B
|
|
{
|
|
T a1;
|
|
|
|
public:
|
|
backend1() : B(), a1()
|
|
{
|
|
}
|
|
|
|
T const& get_a1() const
|
|
{
|
|
return this->a1;
|
|
}
|
|
|
|
protected:
|
|
template <typename ArgPack>
|
|
void initialize_impl(ArgPack const& args)
|
|
{
|
|
B::initialize_impl(args);
|
|
this->a1 = args[_a1];
|
|
}
|
|
};
|
|
|
|
template <typename B, typename T>
|
|
class backend2 : public B
|
|
{
|
|
T a2;
|
|
|
|
public:
|
|
backend2() : B(), a2()
|
|
{
|
|
}
|
|
|
|
T const& get_a2() const
|
|
{
|
|
return this->a2;
|
|
}
|
|
|
|
protected:
|
|
template <typename ArgPack>
|
|
void initialize_impl(ArgPack const& args)
|
|
{
|
|
B::initialize_impl(args);
|
|
this->a2 = args[_a2];
|
|
}
|
|
};
|
|
</pre>
|
|
<p>This example shows that while <tt class="docutils literal">backend0</tt> must always be the root base class
|
|
template and that <tt class="docutils literal">frontend</tt> must always be the most derived class template,
|
|
the other back-ends can be chained together in different orders.</p>
|
|
<pre class="literal-block">
|
|
char const* p = "foo";
|
|
frontend<
|
|
backend2<backend1<backend0<char const*>, char>, int>
|
|
> composed_obj0;
|
|
frontend<
|
|
backend1<backend2<backend0<char const*>, int>, char>
|
|
> composed_obj1;
|
|
composed_obj0.initialize(_a2 = 4, _a1 = ' ', _a0 = p);
|
|
composed_obj1.initialize(_a0 = p, _a1 = ' ', _a2 = 4);
|
|
BOOST_TEST_EQ(composed_obj0.get_a0(), composed_obj1.get_a0());
|
|
BOOST_TEST_EQ(composed_obj0.get_a1(), composed_obj1.get_a1());
|
|
BOOST_TEST_EQ(composed_obj0.get_a2(), composed_obj1.get_a2());
|
|
</pre>
|
|
<p>The <a class="reference external" href="../../test/parameterized_inheritance.cpp">parameterized_inheritance.cpp</a> and <a class="reference external" href="../../test/preprocessor_eval_cat_no_spec.cpp">preprocessor_eval_cat_no_spec.cpp</a> test
|
|
programs demonstrate proper usage of this macro.</p>
|
|
<p><strong>Macro parameters:</strong></p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">result</tt> is the parenthesized return type of the function.</li>
|
|
<li><tt class="docutils literal">name</tt> is the base name of the function; it determines the name of the
|
|
generated implementation function. <tt class="docutils literal">name</tt> may be qualified by the
|
|
<tt class="docutils literal">static</tt> keyword to declare the member function and its helpers as not
|
|
associated with any object of the enclosing type.</li>
|
|
</ul>
|
|
<p><strong>Argument specifiers syntax:</strong></p>
|
|
<p>None.</p>
|
|
<p><strong>Approximate expansion:</strong></p>
|
|
<pre class="literal-block">
|
|
// If <strong>result</strong> is a template instantiation of <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if_c</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if_c</a>, or
|
|
// <a class="reference external" href="http://en.cppreference.com/w/cpp/types/enable_if">std::enable_if</a>:
|
|
template <typename TaggedArg0, typename ...TaggedArgs>
|
|
using boost_param_no_spec_result_ ## __LINE__ ## <strong>name</strong> = <strong>result</strong>;
|
|
|
|
// If <strong>result</strong> is a simple return type:
|
|
template <typename TaggedArg0, typename ...TaggedArgs>
|
|
struct boost_param_no_spec_result_ ## __LINE__ ## <strong>name</strong>
|
|
{
|
|
typedef <strong>result</strong> type;
|
|
};
|
|
|
|
template <typename TaggedArg0, typename ...TaggedArgs>
|
|
inline typename <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if</a><
|
|
<a class="reference internal" href="#are-tagged-arguments"><tt class="docutils literal">are_tagged_arguments</tt></a><TaggedArg0,TaggedArgs...>
|
|
, boost_param_no_spec_result_ ## __LINE__ ## <strong>name</strong><
|
|
TaggedArg0
|
|
, TaggedArgs...
|
|
>
|
|
>::type
|
|
<strong>name</strong>(TaggedArg0 const& arg0, TaggedArgs const&... args)
|
|
{
|
|
return this->boost_param_no_spec_impl ## __LINE__ ## <strong>name</strong>(
|
|
static_cast<
|
|
typename
|
|
boost_param_no_spec_result_ ## __LINE__ ## <strong>name</strong><
|
|
TaggedArg0
|
|
, TaggedArgs...
|
|
>::type(*)()
|
|
>(<a class="reference external" href="http://en.cppreference.com/w/cpp/language/nullptr">std::nullptr</a>)
|
|
, <a class="reference internal" href="#compose"><tt class="docutils literal">compose</tt></a>(arg0, args...)
|
|
);
|
|
}
|
|
|
|
template <typename ResultType, typename Args>
|
|
ResultType
|
|
boost_param_no_spec_impl ## __LINE__ ## <strong>name</strong>(
|
|
(ResultType(*)())
|
|
, Args const& args
|
|
)
|
|
</pre>
|
|
<p>Only the <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> type <tt class="docutils literal">Args</tt> and its object instance <tt class="docutils literal">args</tt> are
|
|
available for use within the function body.</p>
|
|
</div>
|
|
<div class="section" id="boost-parameter-no-spec-const-member-function-result-name">
|
|
<span id="boost-parameter-no-spec-const-member-function"></span><h2><a class="toc-backref" href="#id70">7.14 <tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_CONST_MEMBER_FUNCTION(result, name)</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_no_spec.hpp">boost/parameter/preprocessor_no_spec.hpp</a></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>Generates a member function that can take in named 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">Example usage:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>The return type of each of the following function templates falls under a
|
|
different value category.</p>
|
|
<pre class="literal-block">
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> rvalue_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const rvalue_const_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>& lvalue_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> lset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return lset;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const& lvalue_const_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const clset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return clset;
|
|
}
|
|
</pre>
|
|
<p>The <tt class="docutils literal"><span class="pre">U::evaluate_category</span></tt> static member function template has a simple job:
|
|
to return the correct value category when passed in an object returned by one
|
|
of the functions defined above. Assume that
|
|
<a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> is defined.</p>
|
|
<pre class="literal-block">
|
|
enum invoked
|
|
{
|
|
passed_by_lvalue_reference_to_const
|
|
, passed_by_lvalue_reference
|
|
, passed_by_rvalue_reference_to_const
|
|
, passed_by_rvalue_reference
|
|
};
|
|
|
|
struct U
|
|
{
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&)
|
|
{
|
|
return passed_by_lvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&)
|
|
{
|
|
return passed_by_lvalue_reference;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&&)
|
|
{
|
|
return passed_by_rvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&&)
|
|
{
|
|
return passed_by_rvalue_reference;
|
|
}
|
|
};
|
|
</pre>
|
|
<p>Named parameters are required when invoking the member function; however, none
|
|
of their tags need to be in the same namespace.</p>
|
|
<pre class="literal-block">
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lrc, kw0) in(lrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lr, kw1) in_out(lr))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rrc, kw2) in(rrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rr, kw3) consume(rr))
|
|
</pre>
|
|
<p>Use the macro as a substitute for a variadic function header. Enclose the
|
|
return type <tt class="docutils literal">bool</tt> in parentheses. The macro will qualify the function with
|
|
the <tt class="docutils literal">const</tt> keyword.</p>
|
|
<pre class="literal-block">
|
|
struct D
|
|
{
|
|
D()
|
|
{
|
|
}
|
|
|
|
BOOST_PARAMETER_NO_SPEC_CONST_MEMBER_FUNCTION((bool), evaluate_m)
|
|
{
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference_to_const
|
|
, U::evaluate_category<0>(args[_lrc])
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference
|
|
, U::evaluate_category<1>(args[_lr])
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference_to_const
|
|
, U::evaluate_category<2>(
|
|
args[_rrc | rvalue_const_bitset<2>()]
|
|
)
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference
|
|
, U::evaluate_category<3>(
|
|
args[_rr | rvalue_bitset<3>()]
|
|
)
|
|
);
|
|
|
|
return true;
|
|
}
|
|
};
|
|
</pre>
|
|
<p>To invoke the member function, bind all its arguments to named parameters.</p>
|
|
<pre class="literal-block">
|
|
D const d = D();
|
|
d.evaluate_m(
|
|
_rr0 = rvalue_bitset<3>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
, _lr0 = lvalue_bitset<1>()
|
|
, _rrc0 = rvalue_const_bitset<2>()
|
|
);
|
|
d.evaluate_m(
|
|
_lr0 = lvalue_bitset<1>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
);
|
|
</pre>
|
|
<p>The <a class="reference external" href="../../test/preprocessor_eval_cat_no_spec.cpp">preprocessor_eval_cat_no_spec.cpp</a> test program demonstrates proper usage of
|
|
this macro.</p>
|
|
<p><strong>Macro parameters:</strong></p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">result</tt> is the parenthesized return type of the function.</li>
|
|
<li><tt class="docutils literal">name</tt> is the base name of the function; it determines the name of the
|
|
generated implementation function.</li>
|
|
</ul>
|
|
<p><strong>Argument specifiers syntax:</strong></p>
|
|
<p>None.</p>
|
|
<p><strong>Approximate expansion:</strong></p>
|
|
<pre class="literal-block">
|
|
// If <strong>result</strong> is a template instantiation of <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if_c</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if_c</a>, or
|
|
// <a class="reference external" href="http://en.cppreference.com/w/cpp/types/enable_if">std::enable_if</a>:
|
|
template <typename TaggedArg0, typename ...TaggedArgs>
|
|
using boost_param_no_spec_result_const_ ## __LINE__ ## <strong>name</strong> = <strong>result</strong>;
|
|
|
|
// If <strong>result</strong> is a simple return type:
|
|
template <typename TaggedArg0, typename ...TaggedArgs>
|
|
struct boost_param_no_spec_result_const_ ## __LINE__ ## <strong>name</strong>
|
|
{
|
|
typedef <strong>result</strong> type;
|
|
};
|
|
|
|
template <typename TaggedArg0, typename ...TaggedArgs>
|
|
inline typename <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if</a><
|
|
<a class="reference internal" href="#are-tagged-arguments"><tt class="docutils literal">are_tagged_arguments</tt></a><TaggedArg0,TaggedArgs...>
|
|
, boost_param_no_spec_result_const_ ## __LINE__ ## <strong>name</strong><
|
|
TaggedArg0
|
|
, TaggedArgs...
|
|
>
|
|
>::type
|
|
<strong>name</strong>(TaggedArg0 const& arg0, TaggedArgs const&... args) const
|
|
{
|
|
return this->boost_param_no_spec_impl_const ## __LINE__ ## <strong>name</strong>(
|
|
static_cast<
|
|
typename
|
|
boost_param_no_spec_result_const_ ## __LINE__ ## <strong>name</strong><
|
|
TaggedArg0
|
|
, TaggedArgs...
|
|
>::type(*)()
|
|
>(<a class="reference external" href="http://en.cppreference.com/w/cpp/language/nullptr">std::nullptr</a>)
|
|
, <a class="reference internal" href="#compose"><tt class="docutils literal">compose</tt></a>(arg0, args...)
|
|
);
|
|
}
|
|
|
|
template <typename ResultType, typename Args>
|
|
ResultType
|
|
boost_param_no_spec_impl_const ## __LINE__ ## <strong>name</strong>(
|
|
(ResultType(*)())
|
|
, Args const& args
|
|
) const
|
|
</pre>
|
|
<p>Only the <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> type <tt class="docutils literal">Args</tt> and its object instance <tt class="docutils literal">args</tt> are
|
|
available for use within the function body.</p>
|
|
</div>
|
|
<div class="section" id="boost-parameter-no-spec-function-call-operator-result">
|
|
<span id="boost-parameter-no-spec-function-call-operator"></span><h2><a class="toc-backref" href="#id71">7.15 <tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_FUNCTION_CALL_OPERATOR(result)</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_no_spec.hpp">boost/parameter/preprocessor_no_spec.hpp</a></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>Generates a function call operator that can take in named 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">Example usage:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>When designing a front-end class template whose back-end is configurable via
|
|
parameterized inheritance, it can be useful to omit argument specifiers from
|
|
a named-parameter function call operator so that the delegate member functions
|
|
of the back-end classes can enforce their own specifications.</p>
|
|
<pre class="literal-block">
|
|
template <typename B>
|
|
struct frontend : B
|
|
{
|
|
frontend() : B()
|
|
{
|
|
}
|
|
|
|
BOOST_PARAMETER_NO_SPEC_FUNCTION_CALL_OPERATOR((void))
|
|
{
|
|
this->initialize_impl(args);
|
|
}
|
|
};
|
|
</pre>
|
|
<p>Named parameters are required when invoking the function call operator;
|
|
however, none of their tags need to be in the same namespace.</p>
|
|
<pre class="literal-block">
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>(a0)
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>(a1)
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>(a2)
|
|
</pre>
|
|
<p>For this example, each of the back-end class templates requires its own
|
|
parameter to be present in the argument pack. In practice, such parameters
|
|
should be optional, with default values.</p>
|
|
<pre class="literal-block">
|
|
template <typename T>
|
|
class backend0
|
|
{
|
|
T a0;
|
|
|
|
public:
|
|
backend0() : a0()
|
|
{
|
|
}
|
|
|
|
T const& get_a0() const
|
|
{
|
|
return this->a0;
|
|
}
|
|
|
|
protected:
|
|
template <typename ArgPack>
|
|
void initialize_impl(ArgPack const& args)
|
|
{
|
|
this->a0 = args[_a0];
|
|
}
|
|
};
|
|
|
|
template <typename B, typename T>
|
|
class backend1 : public B
|
|
{
|
|
T a1;
|
|
|
|
public:
|
|
backend1() : B(), a1()
|
|
{
|
|
}
|
|
|
|
T const& get_a1() const
|
|
{
|
|
return this->a1;
|
|
}
|
|
|
|
protected:
|
|
template <typename ArgPack>
|
|
void initialize_impl(ArgPack const& args)
|
|
{
|
|
B::initialize_impl(args);
|
|
this->a1 = args[_a1];
|
|
}
|
|
};
|
|
|
|
template <typename B, typename T>
|
|
class backend2 : public B
|
|
{
|
|
T a2;
|
|
|
|
public:
|
|
backend2() : B(), a2()
|
|
{
|
|
}
|
|
|
|
T const& get_a2() const
|
|
{
|
|
return this->a2;
|
|
}
|
|
|
|
protected:
|
|
template <typename ArgPack>
|
|
void initialize_impl(ArgPack const& args)
|
|
{
|
|
B::initialize_impl(args);
|
|
this->a2 = args[_a2];
|
|
}
|
|
};
|
|
</pre>
|
|
<p>This example shows that while <tt class="docutils literal">backend0</tt> must always be the root base class
|
|
template and that <tt class="docutils literal">frontend</tt> must always be the most derived class template,
|
|
the other back-ends can be chained together in different orders.</p>
|
|
<pre class="literal-block">
|
|
char const* p = "foo";
|
|
frontend<
|
|
backend2<backend1<backend0<char const*>, char>, int>
|
|
> composed_obj0;
|
|
frontend<
|
|
backend1<backend2<backend0<char const*>, int>, char>
|
|
> composed_obj1;
|
|
composed_obj0(_a2 = 4, _a1 = ' ', _a0 = p);
|
|
composed_obj1(_a0 = p, _a1 = ' ', _a2 = 4);
|
|
BOOST_TEST_EQ(composed_obj0.get_a0(), composed_obj1.get_a0());
|
|
BOOST_TEST_EQ(composed_obj0.get_a1(), composed_obj1.get_a1());
|
|
BOOST_TEST_EQ(composed_obj0.get_a2(), composed_obj1.get_a2());
|
|
</pre>
|
|
<p>The <a class="reference external" href="../../test/parameterized_inheritance.cpp">parameterized_inheritance.cpp</a> and <a class="reference external" href="../../test/preprocessor_eval_cat_no_spec.cpp">preprocessor_eval_cat_no_spec.cpp</a> test
|
|
programs demonstrate proper usage of this macro.</p>
|
|
<p><strong>Macro parameters:</strong></p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">result</tt> is the parenthesized return type of the function call operator.</li>
|
|
</ul>
|
|
<p><strong>Argument specifiers syntax:</strong></p>
|
|
<p>None.</p>
|
|
<p><strong>Approximate expansion:</strong></p>
|
|
<pre class="literal-block">
|
|
// If <strong>result</strong> is a template instantiation of <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if_c</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if_c</a>, or
|
|
// <a class="reference external" href="http://en.cppreference.com/w/cpp/types/enable_if">std::enable_if</a>:
|
|
template <typename TaggedArg0, typename ...TaggedArgs>
|
|
using boost_param_no_spec_result_ ## __LINE__ ## operator = <strong>result</strong>;
|
|
|
|
// If <strong>result</strong> is a simple return type:
|
|
template <typename TaggedArg0, typename ...TaggedArgs>
|
|
struct boost_param_no_spec_result_ ## __LINE__ ## operator
|
|
{
|
|
typedef <strong>result</strong> type;
|
|
};
|
|
|
|
template <typename TaggedArg0, typename ...TaggedArgs>
|
|
inline typename <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if</a><
|
|
<a class="reference internal" href="#are-tagged-arguments"><tt class="docutils literal">are_tagged_arguments</tt></a><TaggedArg0,TaggedArgs...>
|
|
, boost_param_no_spec_result_ ## __LINE__ ## operator<
|
|
TaggedArg0
|
|
, TaggedArgs...
|
|
>
|
|
>::type
|
|
operator()(TaggedArg0 const& arg0, TaggedArgs const&... args)
|
|
{
|
|
return this->boost_param_no_spec_impl ## __LINE__ ## operator(
|
|
static_cast<
|
|
typename
|
|
boost_param_no_spec_result_ ## __LINE__ ## operator<
|
|
TaggedArg0
|
|
, TaggedArgs...
|
|
>::type(*)()
|
|
>(<a class="reference external" href="http://en.cppreference.com/w/cpp/language/nullptr">std::nullptr</a>)
|
|
, <a class="reference internal" href="#compose"><tt class="docutils literal">compose</tt></a>(arg0, args...)
|
|
);
|
|
}
|
|
|
|
template <typename ResultType, typename Args>
|
|
ResultType
|
|
boost_param_no_spec_impl ## __LINE__ ## operator(
|
|
(ResultType(*)())
|
|
, Args const& args
|
|
)
|
|
</pre>
|
|
<p>Only the <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> type <tt class="docutils literal">Args</tt> and its object instance <tt class="docutils literal">args</tt> are
|
|
available for use within the function body.</p>
|
|
</div>
|
|
<div class="section" id="boost-parameter-no-spec-const-function-call-operator-result">
|
|
<span id="boost-parameter-no-spec-const-function-call-operator"></span><h2><a class="toc-backref" href="#id72">7.16 <tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_CONST_FUNCTION_CALL_OPERATOR(result)</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_no_spec.hpp">boost/parameter/preprocessor_no_spec.hpp</a></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>Generates a function call operator that can take in named 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">Example usage:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>The return type of each of the following function templates falls under a
|
|
different value category.</p>
|
|
<pre class="literal-block">
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> rvalue_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const rvalue_const_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>& lvalue_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> lset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return lset;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const& lvalue_const_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const clset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return clset;
|
|
}
|
|
</pre>
|
|
<p>The <tt class="docutils literal"><span class="pre">U::evaluate_category</span></tt> static member function template has a simple job:
|
|
to return the correct value category when passed in an object returned by one
|
|
of the functions defined above. Assume that
|
|
<a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> is defined.</p>
|
|
<pre class="literal-block">
|
|
enum invoked
|
|
{
|
|
passed_by_lvalue_reference_to_const
|
|
, passed_by_lvalue_reference
|
|
, passed_by_rvalue_reference_to_const
|
|
, passed_by_rvalue_reference
|
|
};
|
|
|
|
struct U
|
|
{
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&)
|
|
{
|
|
return passed_by_lvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&)
|
|
{
|
|
return passed_by_lvalue_reference;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&&)
|
|
{
|
|
return passed_by_rvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&&)
|
|
{
|
|
return passed_by_rvalue_reference;
|
|
}
|
|
};
|
|
</pre>
|
|
<p>Named parameters are required when invoking the function call operator;
|
|
however, none of their tags need to be in the same namespace.</p>
|
|
<pre class="literal-block">
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lrc, kw0) in(lrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lr, kw1) in_out(lr))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rrc, kw2) in(rrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rr, kw3) consume(rr))
|
|
</pre>
|
|
<p>Use the macro as a substitute for a variadic function call operator
|
|
header. Enclose the return type <tt class="docutils literal">bool</tt> in parentheses. The macro will
|
|
qualify the function with the <tt class="docutils literal">const</tt> keyword.</p>
|
|
<pre class="literal-block">
|
|
struct D
|
|
{
|
|
D()
|
|
{
|
|
}
|
|
|
|
BOOST_PARAMETER_NO_SPEC_CONST_FUNCTION_CALL_OPERATOR((bool))
|
|
{
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference_to_const
|
|
, U::evaluate_category<0>(args[_lrc])
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference
|
|
, U::evaluate_category<1>(args[_lr])
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference_to_const
|
|
, U::evaluate_category<2>(
|
|
args[_rrc | rvalue_const_bitset<2>()]
|
|
)
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference
|
|
, U::evaluate_category<3>(
|
|
args[_rr | rvalue_bitset<3>()]
|
|
)
|
|
);
|
|
|
|
return true;
|
|
}
|
|
};
|
|
</pre>
|
|
<p>To invoke the function call operator, bind all its arguments to named
|
|
parameters.</p>
|
|
<pre class="literal-block">
|
|
D const d = D();
|
|
d(
|
|
_rr0 = rvalue_bitset<3>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
, _lr0 = lvalue_bitset<1>()
|
|
, _rrc0 = rvalue_const_bitset<2>()
|
|
);
|
|
d(
|
|
_lr0 = lvalue_bitset<1>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
);
|
|
</pre>
|
|
<p>The <a class="reference external" href="../../test/preprocessor_eval_cat_no_spec.cpp">preprocessor_eval_cat_no_spec.cpp</a> test program demonstrates proper usage of this
|
|
macro.</p>
|
|
<p><strong>Macro parameters:</strong></p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">result</tt> is the parenthesized return type of the function call operator.</li>
|
|
</ul>
|
|
<p><strong>Argument specifiers syntax:</strong></p>
|
|
<p>None.</p>
|
|
<p><strong>Approximate expansion:</strong></p>
|
|
<pre class="literal-block">
|
|
// If <strong>result</strong> is a template instantiation of <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if_c</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::disable_if_c</a>,
|
|
// <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if</a>, <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_disable_if_c</a>, or
|
|
// <a class="reference external" href="http://en.cppreference.com/w/cpp/types/enable_if">std::enable_if</a>:
|
|
template <typename TaggedArg0, typename ...TaggedArgs>
|
|
using boost_param_no_spec_result_const_ ## __LINE__ ## operator = <strong>result</strong>;
|
|
|
|
// If <strong>result</strong> is a simple return type:
|
|
template <typename TaggedArg0, typename ...TaggedArgs>
|
|
struct boost_param_no_spec_result_const_ ## __LINE__ ## operator
|
|
{
|
|
typedef <strong>result</strong> type;
|
|
};
|
|
|
|
template <typename TaggedArg0, typename ...TaggedArgs>
|
|
inline typename <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::lazy_enable_if</a><
|
|
<a class="reference internal" href="#are-tagged-arguments"><tt class="docutils literal">are_tagged_arguments</tt></a><TaggedArg0,TaggedArgs...>
|
|
, boost_param_no_spec_result_const_ ## __LINE__ ## operator<
|
|
TaggedArg0
|
|
, TaggedArgs...
|
|
>
|
|
>::type
|
|
operator()(
|
|
TaggedArg0 const& arg0
|
|
, TaggedArgs const&... args
|
|
) const
|
|
{
|
|
return this->boost_param_no_spec_impl_const ## __LINE__ ## operator(
|
|
static_cast<
|
|
typename
|
|
boost_param_no_spec_result_const_ ## __LINE__ ## operator<
|
|
TaggedArg0
|
|
, TaggedArgs...
|
|
>::type(*)()
|
|
>(<a class="reference external" href="http://en.cppreference.com/w/cpp/language/nullptr">std::nullptr</a>)
|
|
, <a class="reference internal" href="#compose"><tt class="docutils literal">compose</tt></a>(arg0, args...)
|
|
);
|
|
}
|
|
|
|
template <typename ResultType, typename Args>
|
|
ResultType
|
|
boost_param_no_spec_impl_const ## __LINE__ ## operator(
|
|
(ResultType(*)())
|
|
, Args const& args
|
|
) const
|
|
</pre>
|
|
<p>Only the <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> type <tt class="docutils literal">Args</tt> and its object instance <tt class="docutils literal">args</tt> are
|
|
available for use within the function body.</p>
|
|
</div>
|
|
<div class="section" id="boost-parameter-no-spec-constructor-cls-impl">
|
|
<span id="boost-parameter-no-spec-constructor"></span><h2><a class="toc-backref" href="#id73">7.17 <tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_CONSTRUCTOR(cls, impl)</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_no_spec.hpp">boost/parameter/preprocessor_no_spec.hpp</a></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>Generates a constructor that can take in named 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">Example usage:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>When designing a front-end class template whose back-end is configurable via
|
|
parameterized inheritance, it can be useful to omit argument specifiers from
|
|
a named-parameter constructor so that the delegate constructors of the
|
|
back-end classes can enforce their own specifications.</p>
|
|
<pre class="literal-block">
|
|
template <typename B>
|
|
struct frontend : B
|
|
{
|
|
BOOST_PARAMETER_NO_SPEC_CONSTRUCTOR(frontend, (B))
|
|
};
|
|
</pre>
|
|
<p>Named parameters are required when invoking the constructor; however, none of
|
|
their tags need to be in the same namespace.</p>
|
|
<pre class="literal-block">
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>(a0)
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>(a1)
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>(a2)
|
|
</pre>
|
|
<p>For this example, each of the back-end class templates requires its own
|
|
parameter to be present in the argument pack. In practice, such parameters
|
|
should be optional, with default values.</p>
|
|
<pre class="literal-block">
|
|
struct _enabler
|
|
{
|
|
};
|
|
|
|
template <typename T>
|
|
class backend0
|
|
{
|
|
T a0;
|
|
|
|
public:
|
|
template <typename ArgPack>
|
|
explicit backend0(
|
|
ArgPack const& args
|
|
, typename <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a><
|
|
<a class="reference internal" href="#is-argument-pack"><tt class="docutils literal">is_argument_pack</tt></a><ArgPack>
|
|
, _enabler
|
|
>::type = _enabler()
|
|
) : a0(args[_a0])
|
|
{
|
|
}
|
|
|
|
T const& get_a0() const
|
|
{
|
|
return this->a0;
|
|
}
|
|
};
|
|
|
|
template <typename B, typename T>
|
|
class backend1 : public B
|
|
{
|
|
T a1;
|
|
|
|
public:
|
|
template <typename ArgPack>
|
|
explicit backend1(
|
|
ArgPack const& args
|
|
, typename <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a><
|
|
<a class="reference internal" href="#is-argument-pack"><tt class="docutils literal">is_argument_pack</tt></a><ArgPack>
|
|
, _enabler
|
|
>::type = _enabler()
|
|
) : B(args), a1(args[_a1])
|
|
{
|
|
}
|
|
|
|
T const& get_a1() const
|
|
{
|
|
return this->a1;
|
|
}
|
|
};
|
|
|
|
template <typename B, typename T>
|
|
class backend2 : public B
|
|
{
|
|
T a2;
|
|
|
|
public:
|
|
template <typename ArgPack>
|
|
explicit backend2(
|
|
ArgPack const& args
|
|
, typename <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a><
|
|
<a class="reference internal" href="#is-argument-pack"><tt class="docutils literal">is_argument_pack</tt></a><ArgPack>
|
|
, _enabler
|
|
>::type = _enabler()
|
|
) : B(args), a2(args[_a2])
|
|
{
|
|
}
|
|
|
|
T const& get_a2() const
|
|
{
|
|
return this->a2;
|
|
}
|
|
};
|
|
</pre>
|
|
<p>This example shows that while <tt class="docutils literal">backend0</tt> must always be the root base class
|
|
template and that <tt class="docutils literal">frontend</tt> must always be the most derived class template,
|
|
the other back-ends can be chained together in different orders.</p>
|
|
<pre class="literal-block">
|
|
char const* p = "foo";
|
|
frontend<
|
|
backend2<backend1<backend0<char const*>, char>, int>
|
|
> composed_obj0(_a2 = 4, _a1 = ' ', _a0 = p);
|
|
frontend<
|
|
backend1<backend2<backend0<char const*>, int>, char>
|
|
> composed_obj1(_a0 = p, _a1 = ' ', _a2 = 4);
|
|
BOOST_TEST_EQ(composed_obj0.get_a0(), composed_obj1.get_a0());
|
|
BOOST_TEST_EQ(composed_obj0.get_a1(), composed_obj1.get_a1());
|
|
BOOST_TEST_EQ(composed_obj0.get_a2(), composed_obj1.get_a2());
|
|
</pre>
|
|
<p>The <a class="reference external" href="../../test/parameterized_inheritance.cpp">parameterized_inheritance.cpp</a> and <a class="reference external" href="../../test/preprocessor_eval_cat_no_spec.cpp">preprocessor_eval_cat_no_spec.cpp</a> test
|
|
programs demonstrate proper usage of this macro.</p>
|
|
<p><strong>Macro parameters:</strong></p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">cls</tt> is the name of the enclosing class.</li>
|
|
<li><tt class="docutils literal">impl</tt> is the parenthesized implementation base class for <tt class="docutils literal">cls</tt>.</li>
|
|
</ul>
|
|
<p><strong>Argument specifiers syntax:</strong></p>
|
|
<p>None.</p>
|
|
<p><strong>Approximate expansion:</strong></p>
|
|
<pre class="literal-block">
|
|
template <
|
|
typename TaggedArg0
|
|
, typename ...TaggedArgs
|
|
, typename = typename <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a><
|
|
<a class="reference internal" href="#are-tagged-arguments"><tt class="docutils literal">are_tagged_arguments</tt></a><TaggedArg0,TaggedArgs...>
|
|
>::type
|
|
>
|
|
inline explicit <strong>cls</strong>(
|
|
TaggedArg0 const& arg0
|
|
, TaggedArgs const&... args
|
|
) : <strong>impl</strong>(<a class="reference internal" href="#compose"><tt class="docutils literal">compose</tt></a>(arg0, args...))
|
|
{
|
|
}
|
|
</pre>
|
|
</div>
|
|
<div class="section" id="boost-parameter-no-spec-no-base-constructor-cls-impl">
|
|
<span id="boost-parameter-no-spec-no-base-constructor"></span><h2><a class="toc-backref" href="#id74">7.18 <tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_NO_BASE_CONSTRUCTOR(cls, impl)</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_no_spec.hpp">boost/parameter/preprocessor_no_spec.hpp</a></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>Generates a constructor that can take in named 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">Example usage:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>The return type of each of the following function templates falls under a
|
|
different value category.</p>
|
|
<pre class="literal-block">
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> rvalue_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const rvalue_const_bitset()
|
|
{
|
|
return <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>& lvalue_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> lset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return lset;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const& lvalue_const_bitset()
|
|
{
|
|
static <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const clset = <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>();
|
|
return clset;
|
|
}
|
|
</pre>
|
|
<p>The <tt class="docutils literal"><span class="pre">U::evaluate_category</span></tt> static member function template has a simple job:
|
|
to return the correct value category when passed in an object returned by one
|
|
of the functions defined above. Assume that
|
|
<a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> is defined.</p>
|
|
<pre class="literal-block">
|
|
enum invoked
|
|
{
|
|
passed_by_lvalue_reference_to_const
|
|
, passed_by_lvalue_reference
|
|
, passed_by_rvalue_reference_to_const
|
|
, passed_by_rvalue_reference
|
|
};
|
|
|
|
struct U
|
|
{
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&)
|
|
{
|
|
return passed_by_lvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&)
|
|
{
|
|
return passed_by_lvalue_reference;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1> const&&)
|
|
{
|
|
return passed_by_rvalue_reference_to_const;
|
|
}
|
|
|
|
template <std::size_t N>
|
|
static invoked evaluate_category(<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/bitset">std::bitset</a><N + 1>&&)
|
|
{
|
|
return passed_by_rvalue_reference;
|
|
}
|
|
};
|
|
</pre>
|
|
<p>Named parameters are required when invoking the constructor; however, none of
|
|
their tags need to be in the same namespace.</p>
|
|
<pre class="literal-block">
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lrc, kw0) in(lrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_lr, kw1) in_out(lr))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rrc, kw2) in(rrc))
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>((_rr, kw3) consume(rr))
|
|
</pre>
|
|
<p>Unlike <a class="reference internal" href="#boost-parameter-no-spec-constructor"><tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_CONSTRUCTOR</tt></a>, this macro doesn't require a
|
|
base class, only a delegate function to which the generated constructor can
|
|
pass its <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a>.</p>
|
|
<pre class="literal-block">
|
|
struct D
|
|
{
|
|
BOOST_PARAMETER_NO_SPEC_NO_BASE_CONSTRUCTOR(D, D::_evaluate)
|
|
|
|
private:
|
|
template <typename Args>
|
|
static bool _evaluate(Args const& args)
|
|
{
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference_to_const
|
|
, U::evaluate_category<0>(args[_lrc])
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_lvalue_reference
|
|
, U::evaluate_category<1>(args[_lr])
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference_to_const
|
|
, U::evaluate_category<2>(
|
|
args[_rrc | rvalue_const_bitset<2>()]
|
|
)
|
|
);
|
|
BOOST_TEST_EQ(
|
|
passed_by_rvalue_reference
|
|
, U::evaluate_category<3>(
|
|
args[_rr | rvalue_bitset<3>()]
|
|
)
|
|
);
|
|
|
|
return true;
|
|
}
|
|
};
|
|
</pre>
|
|
<p>To invoke the constructor, bind all its arguments to named parameters.</p>
|
|
<pre class="literal-block">
|
|
D dp0(
|
|
_rr0 = rvalue_bitset<3>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
, _lr0 = lvalue_bitset<1>()
|
|
, _rrc0 = rvalue_const_bitset<2>()
|
|
);
|
|
D dp1(
|
|
_lr0 = lvalue_bitset<1>()
|
|
, _lrc0 = lvalue_const_bitset<0>()
|
|
);
|
|
</pre>
|
|
<p>The <a class="reference external" href="../../test/preprocessor_eval_cat_no_spec.cpp">preprocessor_eval_cat_no_spec.cpp</a> test program demonstrates proper usage of
|
|
this macro.</p>
|
|
<p><strong>Macro parameters:</strong></p>
|
|
<ul class="simple">
|
|
<li><tt class="docutils literal">cls</tt> is the name of the enclosing class.</li>
|
|
<li><tt class="docutils literal">func</tt> is a function that takes in the <a class="reference internal" href="#argumentpack"><span class="concept">ArgumentPack</span></a> that the
|
|
generated constructor passes on.</li>
|
|
</ul>
|
|
<p><strong>Argument specifiers syntax:</strong></p>
|
|
<p>None.</p>
|
|
<p><strong>Approximate expansion:</strong></p>
|
|
<pre class="literal-block">
|
|
template <
|
|
typename TaggedArg0
|
|
, typename ...TaggedArgs
|
|
, typename = typename <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a><
|
|
<a class="reference internal" href="#are-tagged-arguments"><tt class="docutils literal">are_tagged_arguments</tt></a><TaggedArg0,TaggedArgs...>
|
|
>::type
|
|
>
|
|
inline explicit <strong>cls</strong>(
|
|
TaggedArg0 const& arg0
|
|
, TaggedArgs const&... args
|
|
)
|
|
{
|
|
<strong>func</strong>(<a class="reference internal" href="#compose"><tt class="docutils literal">compose</tt></a>(arg0, args...));
|
|
}
|
|
</pre>
|
|
</div>
|
|
<div class="section" id="boost-parameter-name-name">
|
|
<span id="boost-parameter-name"></span><h2><a class="toc-backref" href="#id75">7.19 <tt class="docutils literal">BOOST_PARAMETER_NAME(name)</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/name.hpp">boost/parameter/name.hpp</a></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>Declares a tag-type and keyword object.</p>
|
|
<p><strong>If</strong> <em>name</em> is of the form:</p>
|
|
<pre class="literal-block">
|
|
(<em>object-name</em>, <em>namespace-name</em>) <em>qualifier</em>(<em>tag-name</em>)
|
|
</pre>
|
|
<p><strong>then</strong></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">Requires:</th><td class="field-body"><em>qualifier</em> is either <tt class="docutils literal">in</tt>, <tt class="docutils literal">out</tt>, <tt class="docutils literal">in_out</tt>, <tt class="docutils literal">consume</tt>,
|
|
<tt class="docutils literal">move_from</tt>, or <tt class="docutils literal">forward</tt>.</td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Expands to:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<pre class="literal-block">
|
|
namespace <em>namespace-name</em> {
|
|
|
|
struct <em>tag-name</em>
|
|
{
|
|
static constexpr char const* keyword_name()
|
|
{
|
|
return ## <em>tag-name</em>;
|
|
}
|
|
|
|
typedef <em>unspecified</em> _;
|
|
typedef <em>unspecified</em> _1;
|
|
typedef boost::parameter::<em>qualifier</em> ## _reference qualifier;
|
|
|
|
// The following definitions are available only when
|
|
// <a class="reference internal" href="#boost-parameter-can-use-mp11"><tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt></a> is defined.
|
|
|
|
template <typename ArgumentPack>
|
|
using binding_fn = typename <a class="reference internal" href="#binding"><tt class="docutils literal">binding</tt></a><
|
|
ArgumentPack
|
|
, <em>tag-name</em>
|
|
>::type;
|
|
|
|
template <typename ArgumentPack>
|
|
using fn = typename <a class="reference internal" href="#value-type"><tt class="docutils literal">value_type</tt></a><ArgumentPack, <em>tag-name</em>>::type;
|
|
};
|
|
}
|
|
|
|
<a class="reference internal" href="#keyword"><tt class="docutils literal">keyword</tt></a><<em>tag-namespace</em>::<em>tag-name</em>> const& <em>object-name</em>
|
|
= <a class="reference internal" href="#keyword"><tt class="docutils literal">keyword</tt></a><<em>tag-namespace</em>::<em>tag-name</em>>::instance;
|
|
</pre>
|
|
<p><strong>Else 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>
|
|
<p>Treats <em>name</em> as if it were of the form:</p>
|
|
<pre class="literal-block">
|
|
(forward(<em>tag-name</em>), <em>namespace-name</em>) <em>object-name</em>
|
|
</pre>
|
|
<p><strong>Else If</strong> <em>name</em> is of the form:</p>
|
|
<pre class="literal-block">
|
|
<em>qualifier</em>(<em>tag-name</em>)
|
|
</pre>
|
|
<p><strong>then</strong></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">Requires:</th><td class="field-body"><em>qualifier</em> is either <tt class="docutils literal">in</tt>, <tt class="docutils literal">out</tt>, <tt class="docutils literal">in_out</tt>, <tt class="docutils literal">consume</tt>,
|
|
<tt class="docutils literal">move_from</tt>, or <tt class="docutils literal">forward</tt>.</td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Expands to:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<pre class="literal-block">
|
|
namespace tag {
|
|
|
|
struct <em>tag-name</em>
|
|
{
|
|
static constexpr char const* keyword_name()
|
|
{
|
|
return ## <em>tag-name</em>;
|
|
}
|
|
|
|
typedef <em>unspecified</em> _;
|
|
typedef <em>unspecified</em> _1;
|
|
typedef boost::parameter::<em>qualifier</em> ## _reference qualifier;
|
|
|
|
// The following definitions are available only when
|
|
// <a class="reference internal" href="#boost-parameter-can-use-mp11"><tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt></a> is defined.
|
|
|
|
template <typename ArgumentPack>
|
|
using binding_fn = typename <a class="reference internal" href="#binding"><tt class="docutils literal">binding</tt></a><
|
|
ArgumentPack
|
|
, <em>tag-name</em>
|
|
>::type;
|
|
|
|
template <typename ArgumentPack>
|
|
using fn = typename <a class="reference internal" href="#value-type"><tt class="docutils literal">value_type</tt></a><ArgumentPack, <em>tag-name</em>>::type;
|
|
};
|
|
}
|
|
|
|
<a class="reference internal" href="#keyword"><tt class="docutils literal">keyword</tt></a><tag::<em>tag-name</em>> const& _ ## <em>tag-name</em>
|
|
= <a class="reference internal" href="#keyword"><tt class="docutils literal">keyword</tt></a><tag::<em>tag-name</em>>::instance;
|
|
</pre>
|
|
<p><strong>Else</strong></p>
|
|
<p>Treats <em>name</em> as if it were of the form:</p>
|
|
<pre class="literal-block">
|
|
forward(<em>tag-name</em>)
|
|
</pre>
|
|
</div>
|
|
<div class="section" id="boost-parameter-nested-keyword-tag-namespace-name-alias">
|
|
<span id="boost-parameter-nested-keyword"></span><h2><a class="toc-backref" href="#id76">7.20 <tt class="docutils literal">BOOST_PARAMETER_NESTED_KEYWORD(tag_namespace, name, alias)</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/nested_keyword.hpp">boost/parameter/nested_keyword.hpp</a></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>Declares a tag-type, a keyword object, and an alias for that object nested in
|
|
the tag-type.</p>
|
|
<p><strong>If</strong> <em>name</em> is of the form:</p>
|
|
<pre class="literal-block">
|
|
<em>qualifier</em>(<em>tag-name</em>)
|
|
</pre>
|
|
<p><strong>then</strong></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">Requires:</th><td class="field-body"><em>qualifier</em> is either <tt class="docutils literal">in</tt>, <tt class="docutils literal">out</tt>, <tt class="docutils literal">in_out</tt>, <tt class="docutils literal">consume</tt>,
|
|
<tt class="docutils literal">move_from</tt>, or <tt class="docutils literal">forward</tt>.</td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Expands to:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<pre class="literal-block">
|
|
namespace tag {
|
|
|
|
struct <em>tag-name</em>
|
|
{
|
|
static constexpr char const* keyword_name()
|
|
{
|
|
return ## <em>tag-name</em> ## _;
|
|
}
|
|
|
|
typedef <em>unspecified</em> _;
|
|
typedef <em>unspecified</em> _1;
|
|
typedef boost::parameter::<em>qualifier</em> ## _reference qualifier;
|
|
static <a class="reference internal" href="#keyword"><tt class="docutils literal">keyword</tt></a><<em>tag-name</em>> const& <em>alias</em>;
|
|
|
|
// The following definitions are available only when
|
|
// <a class="reference internal" href="#boost-parameter-can-use-mp11"><tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt></a> is defined.
|
|
|
|
template <typename ArgumentPack>
|
|
using binding_fn = typename <a class="reference internal" href="#binding"><tt class="docutils literal">binding</tt></a><
|
|
ArgumentPack
|
|
, <em>tag-name</em>
|
|
>::type;
|
|
|
|
template <typename ArgumentPack>
|
|
using fn = typename <a class="reference internal" href="#value-type"><tt class="docutils literal">value_type</tt></a><ArgumentPack, <em>tag-name</em>>::type;
|
|
};
|
|
|
|
<a class="reference internal" href="#keyword"><tt class="docutils literal">keyword</tt></a><<em>tag-name</em>> const& tag::<em>tag-name</em>::<em>alias</em>
|
|
= <a class="reference internal" href="#keyword"><tt class="docutils literal">keyword</tt></a><<em>tag-name</em>>::instance;
|
|
}
|
|
|
|
<a class="reference internal" href="#keyword"><tt class="docutils literal">keyword</tt></a><tag::<em>tag-name</em>> const& tag::<em>tag-name</em>::<em>name</em>
|
|
= <a class="reference internal" href="#keyword"><tt class="docutils literal">keyword</tt></a><tag::<em>tag-name</em>>::instance;
|
|
</pre>
|
|
<p><strong>Else</strong></p>
|
|
<p>Treats <em>name</em> as if it were of the form:</p>
|
|
<pre class="literal-block">
|
|
forward(<em>tag-name</em>)
|
|
</pre>
|
|
</div>
|
|
<div class="section" id="boost-parameter-template-keyword-name">
|
|
<span id="boost-parameter-template-keyword"></span><h2><a class="toc-backref" href="#id77">7.21 <tt class="docutils literal">BOOST_PARAMETER_TEMPLATE_KEYWORD(name)</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/template_keyword.hpp">boost/parameter/template_keyword.hpp</a></td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Included by:</th><td class="field-body"><a class="reference external" href="../../../../boost/parameter/name.hpp">boost/parameter/name.hpp</a></td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Expands to:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<pre class="literal-block">
|
|
namespace tag {
|
|
|
|
struct <em>name</em>;
|
|
}
|
|
|
|
template <typename T>
|
|
struct <em>name</em> : <a class="reference internal" href="#template-keyword"><tt class="docutils literal">template_keyword</tt></a><tag:: <em>name</em>, T>
|
|
{
|
|
};
|
|
</pre>
|
|
<p>The <a class="reference external" href="../../test/function_type_tpl_param.cpp">function_type_tpl_param.cpp</a> test program demonstrates proper usage of
|
|
this macro.</p>
|
|
</div>
|
|
<div class="section" id="boost-parameter-fun-r-n-l-h-p">
|
|
<span id="boost-parameter-fun"></span><h2><a class="toc-backref" href="#id78">7.22 <tt class="docutils literal">BOOST_PARAMETER_FUN(r, n, l, h, p)</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">BOOST_PARAMETER_FUNCTION</tt>.</p>
|
|
</div>
|
|
<p>Generates a sequence of <a class="reference external" href="index.html#forwarding-functions">forwarding function</a> templates named
|
|
<tt class="docutils literal">n</tt>, with arities ranging from <tt class="docutils literal">l</tt> to <tt class="docutils literal">h</tt>, returning <tt class="docutils literal">r</tt>,
|
|
and using <tt class="docutils literal">p</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 external" href="../../../../boost/parameter/macros.hpp">boost/parameter/macros.hpp</a></td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><tt class="docutils literal">l</tt> and <tt class="docutils literal">h</tt> are nonnegative integer tokens
|
|
such that <tt class="docutils literal">l</tt> < <tt class="docutils literal">h</tt></td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Expands to:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<pre class="literal-block">
|
|
template <typename A1, typename A2, …, typename A ## <strong>l</strong>>
|
|
r
|
|
name(
|
|
A1 && a1, A2 && a2, …, A ## <strong>l</strong> && a ## <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>(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A1>(a1)
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A2>(a2)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>l</strong>>(a ## <strong>l</strong>)
|
|
)
|
|
);
|
|
}
|
|
|
|
template <
|
|
typename A1
|
|
, typename A2
|
|
, …
|
|
, typename A ## <strong>l</strong>
|
|
, typename A ## <a class="reference external" href="../../../preprocessor/doc/ref/inc.html">BOOST_PP_INC</a>(<strong>l</strong>)
|
|
>
|
|
r
|
|
name(
|
|
A1 && a1, A2 && a2, …, A ## <strong>l</strong> && a ## <strong>l</strong>
|
|
, A ## <a class="reference external" href="../../../preprocessor/doc/ref/inc.html">BOOST_PP_INC</a>(<strong>l</strong>) const& a ## <a class="reference external" 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 external" 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>(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A1>(a1)
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A2>(a2)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>l</strong>>(a ## <strong>l</strong>)
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <a class="reference external" href="../../../preprocessor/doc/ref/inc.html">BOOST_PP_INC</a>(<strong>l</strong>)>(
|
|
a ## <a class="reference external" href="../../../preprocessor/doc/ref/inc.html">BOOST_PP_INC</a>(<strong>l</strong>)
|
|
)
|
|
)
|
|
);
|
|
}
|
|
|
|
<span class="vellipsis">⋮</span>
|
|
|
|
template <typename A1, typename A2, …, typename A ## <strong>h</strong>>
|
|
r
|
|
name(
|
|
A1 && a1, A2 && a2, …, A ## <strong>h</strong> && 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>(
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A1>(a1)
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A2>(a2)
|
|
, …
|
|
, <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a><A ## <strong>h</strong>>(a ## <strong>h</strong>)
|
|
)
|
|
);
|
|
}
|
|
</pre>
|
|
<p>The <a class="reference external" href="../../test/macros.cpp">macros.cpp</a> and <a class="reference external" href="../../test/macros_eval_category.cpp">macros_eval_category.cpp</a> test programs demonstrate proper
|
|
usage of this macro.</p>
|
|
</div>
|
|
<div class="section" id="boost-parameter-keyword-n-k">
|
|
<span id="boost-parameter-keyword"></span><h2><a class="toc-backref" href="#id79">7.23 <tt class="docutils literal">BOOST_PARAMETER_KEYWORD(n, k)</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">BOOST_PARAMETER_NAME</tt>.</p>
|
|
</div>
|
|
<p>Generates the declaration of a <a class="reference internal" href="#keyword-tag-type">keyword tag type</a> named <tt class="docutils literal">k</tt> in
|
|
namespace <tt class="docutils literal">n</tt> and a corresponding <a class="reference internal" 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 external" href="../../../../boost/parameter/keyword.hpp">boost/parameter/keyword.hpp</a></td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Expands to:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<pre class="literal-block">
|
|
namespace <strong>n</strong> {
|
|
|
|
struct <strong>k</strong>
|
|
{
|
|
static constexpr char const* keyword_name()
|
|
{
|
|
return ## <em>k</em>;
|
|
}
|
|
|
|
typedef <em>unspecified</em> _;
|
|
typedef <em>unspecified</em> _1;
|
|
typedef boost::parameter::forward_reference qualifier;
|
|
|
|
// The following definitions are available only when
|
|
// <a class="reference internal" href="#boost-parameter-can-use-mp11"><tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt></a> is defined.
|
|
|
|
template <typename ArgumentPack>
|
|
using binding_fn = typename <a class="reference internal" href="#binding"><tt class="docutils literal">binding</tt></a><
|
|
ArgumentPack
|
|
, <em>k</em>
|
|
>::type;
|
|
|
|
template <typename ArgumentPack>
|
|
using fn = typename <a class="reference internal" href="#value-type"><tt class="docutils literal">value_type</tt></a><ArgumentPack, <em>k</em>>::type;
|
|
};
|
|
}
|
|
|
|
namespace {
|
|
|
|
<a class="reference internal" href="#keyword"><tt class="docutils literal">keyword</tt></a><<em>n</em>::<strong>k</strong>> const& <strong>k</strong>
|
|
= <a class="reference internal" href="#keyword"><tt class="docutils literal">keyword</tt></a><<em>n</em>::<strong>k</strong>>::instance;
|
|
}
|
|
</pre>
|
|
</div>
|
|
<div class="section" id="boost-parameter-match-p-a-x">
|
|
<h2><a class="toc-backref" href="#id80">7.24 <tt class="docutils literal">BOOST_PARAMETER_MATCH(p, a, x)</tt></a></h2>
|
|
<p>Generates a defaulted parameter declaration for a <a class="reference external" 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 external" href="../../../../boost/parameter/match.hpp">boost/parameter/match.hpp</a></td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><tt class="docutils literal">a</tt> is a <a class="reference external" href="../../../preprocessor/doc/data.html">Boost.Preprocessor sequence</a> of the form</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<pre class="literal-block">
|
|
(A0)(A1)…(A ## <em>n</em>)
|
|
</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">Expands to:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<pre class="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>
|
|
</div>
|
|
</div>
|
|
<div class="section" id="configuration-macros">
|
|
<h1><a class="toc-backref" href="#id81">8 Configuration Macros</a></h1>
|
|
<div class="section" id="id21">
|
|
<span id="boost-parameter-has-perfect-forwarding"></span><h2><a class="toc-backref" href="#id82">8.1 <tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a></h2>
|
|
<p>Determines whether or not the library supports perfect forwarding, or the
|
|
preservation of parameter value categories. Users can manually disable this
|
|
macro by <tt class="docutils literal">#defining</tt> the <a class="reference internal" href="#boost-parameter-disable-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_DISABLE_PERFECT_FORWARDING</tt></a>
|
|
macro. Otherwise, the library will <tt class="docutils literal">#define</tt> this macro if and only if it
|
|
is not already defined, and if the configuration macros
|
|
<a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__03_defects"><tt class="docutils literal">BOOST_NO_FUNCTION_TEMPLATE_ORDERING</tt></a>, <a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__03_defects"><tt class="docutils literal">BOOST_NO_SFINAE</tt></a>,
|
|
<a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__11_features_not_supported"><tt class="docutils literal">BOOST_NO_CXX11_RVALUE_REFERENCES</tt></a>, <a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__11_features_not_supported"><tt class="docutils literal">BOOST_NO_CXX11_VARIADIC_TEMPLATES</tt></a>, and
|
|
<a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__11_features_not_supported"><tt class="docutils literal">BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS</tt></a> are not already defined by
|
|
<a class="reference external" href="../../../config/doc/html/index.html">Boost.Config</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/config.hpp">boost/parameter/config.hpp</a></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
<div class="section" id="id22">
|
|
<span id="boost-parameter-disable-perfect-forwarding"></span><h2><a class="toc-backref" href="#id83">8.2 <tt class="docutils literal">BOOST_PARAMETER_DISABLE_PERFECT_FORWARDING</tt></a></h2>
|
|
<p>It may be necessary to test user code in case perfect forwarding support is
|
|
unavailable. Users can <tt class="docutils literal">#define</tt> this macro either in their project
|
|
settings or before including any library header files. Doing so will leave
|
|
both <a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> and
|
|
<a class="reference internal" href="#boost-parameter-can-use-mp11"><tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt></a> undefined.</p>
|
|
</div>
|
|
<div class="section" id="id23">
|
|
<span id="boost-parameter-can-use-mp11"></span><h2><a class="toc-backref" href="#id84">8.3 <tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt></a></h2>
|
|
<p>Determines whether or not the library can use <a class="reference external" href="../../../mp11/doc/html/mp11.html">Boost.MP11</a>, a C++11
|
|
metaprogramming library. Users can manually disable this macro by
|
|
<tt class="docutils literal">#defining</tt> the <a class="reference internal" href="#boost-parameter-disable-mp11-usage"><tt class="docutils literal">BOOST_PARAMETER_DISABLE_MP11_USAGE</tt></a> macro or the
|
|
<a class="reference internal" href="#boost-parameter-disable-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_DISABLE_PERFECT_FORWARDING</tt></a> macro. Otherwise, the library
|
|
will <tt class="docutils literal">#define</tt> this macro if and only if it is not already defined, if
|
|
<a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> is defined, and if the configuration
|
|
macros <a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__11_features_not_supported"><tt class="docutils literal">BOOST_NO_CXX11_CONSTEXPR</tt></a>, <a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__11_features_not_supported"><tt class="docutils literal">BOOST_NO_CXX11_DECLTYPE_N3276</tt></a>,
|
|
<a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__11_features_not_supported"><tt class="docutils literal">BOOST_NO_CXX11_AUTO_DECLARATIONS</tt></a>, <a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__11_features_not_supported"><tt class="docutils literal">BOOST_NO_CXX11_TEMPLATE_ALIASES</tt></a>,
|
|
<a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__11_features_not_supported"><tt class="docutils literal">BOOST_NO_CXX11_STATIC_ASSERT</tt></a>, <a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__11_features_not_supported"><tt class="docutils literal">BOOST_NO_CXX11_HDR_TYPE_TRAITS</tt></a>,
|
|
<a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__11_features_not_supported"><tt class="docutils literal">BOOST_NO_CXX11_HDR_INITIALIZER_LIST</tt></a>, and <a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__11_features_not_supported"><tt class="docutils literal">BOOST_NO_CXX11_HDR_TUPLE</tt></a>
|
|
are not already defined by <a class="reference external" href="../../../config/doc/html/index.html">Boost.Config</a>.</p>
|
|
<div class="admonition-usage-note admonition">
|
|
<p class="first admonition-title">Usage Note</p>
|
|
<p class="last"><a class="reference external" href="../../../mp11/doc/html/mp11.html">Boost.MP11</a> and <a class="reference external" href="../../../mpl/doc/index.html">Boost.MPL</a> are <strong>not</strong> mutually exclusive. It's
|
|
perfectly acceptable to specify deduced parameters using both quoted
|
|
metafunctions and metafunction classes, for example. See
|
|
<a class="reference external" href="../../test/evaluate_category.cpp">evaluate_category.cpp</a>.</p>
|
|
</div>
|
|
<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/config.hpp">boost/parameter/config.hpp</a></td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Example usage:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>Given the following definitions:</p>
|
|
<pre class="literal-block">
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>(x)
|
|
|
|
template <typename A0>
|
|
typename <a class="reference external" href="../../../core/doc/html/core/enable_if.html">boost::enable_if</a><<a class="reference external" href="http://en.cppreference.com/w/cpp/types/is_same">std::is_same</a><int,A0>,int>::type
|
|
sfinae(A0 const& a0)
|
|
{
|
|
return 0;
|
|
}
|
|
</pre>
|
|
<p><a class="reference external" href="../../../mp11/doc/html/mp11.html">Boost.MP11</a> allows deduced parameters to be defined more succinctly:</p>
|
|
<pre class="literal-block">
|
|
template <typename T, typename Args>
|
|
using predicate = <a class="reference external" href="http://en.cppreference.com/w/cpp/types/is_convertible">std::is_convertible</a><T,char const*>;
|
|
|
|
<a class="reference internal" href="#boost-parameter-function"><tt class="docutils literal">BOOST_PARAMETER_FUNCTION</tt></a>((int), sfinae, tag,
|
|
(deduced
|
|
(optional
|
|
(x
|
|
, *(<a class="reference external" href="../../../mp11/doc/html/mp11.html#mp_quotef">boost::mp11::mp_quote</a><predicate>)
|
|
, static_cast<char const*>(<a class="reference external" href="http://en.cppreference.com/w/cpp/language/nullptr">std::nullptr</a>)
|
|
)
|
|
)
|
|
)
|
|
)
|
|
{
|
|
return 1;
|
|
}
|
|
</pre>
|
|
<p>Without <a class="reference external" href="../../../mp11/doc/html/mp11.html">Boost.MP11</a>, deduced parameter definitions tend to be more verbose:</p>
|
|
<pre class="literal-block">
|
|
struct predicate
|
|
{
|
|
template <typename T, typename Args>
|
|
struct apply
|
|
: <a class="reference external" href="../../../mpl/doc/refmanual/if.html">mpl::if_</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_convertible.html">boost::is_convertible</a><T,char const*>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> // Still have to convert to a
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::false_</a> // <a class="reference external" href="../../../mpl/doc/refmanual/integral-constant.html">Boolean Integral Constant</a>.
|
|
>
|
|
{
|
|
};
|
|
};
|
|
|
|
<a class="reference internal" href="#boost-parameter-function"><tt class="docutils literal">BOOST_PARAMETER_FUNCTION</tt></a>((int), sfinae, tag,
|
|
(deduced
|
|
(optional
|
|
(x
|
|
, *(predicate)
|
|
, static_cast<char const*>(<a class="reference external" href="http://en.cppreference.com/w/cpp/language/nullptr">std::nullptr</a>)
|
|
)
|
|
)
|
|
)
|
|
)
|
|
{
|
|
return 1;
|
|
}
|
|
</pre>
|
|
<p>Either way, the following assertions will succeed:</p>
|
|
<pre class="literal-block">
|
|
assert(1 == sfinae());
|
|
assert(1 == sfinae("foo"));
|
|
assert(0 == sfinae(1));
|
|
</pre>
|
|
<p>As another example, given the following declarations and definitions:</p>
|
|
<pre class="literal-block">
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>(x)
|
|
<a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a>(y)
|
|
|
|
template <typename E, typename Args>
|
|
void check0(E const& e, Args const& args);
|
|
|
|
template <typename P, typename E, typename ...Args>
|
|
void check(E const& e, Args const&... args)
|
|
{
|
|
check0(e, P()(args...));
|
|
}
|
|
</pre>
|
|
<p>Argument packs qualify as <a class="reference external" href="../../../mp11/doc/html/mp11.html">Boost.MP11</a>-style lists containing
|
|
<a class="reference internal" href="#keyword-tag-type">keyword tag type</a>s:</p>
|
|
<pre class="literal-block">
|
|
template <typename Args>
|
|
struct some_functor
|
|
{
|
|
template <typename K>
|
|
void operator()(K&&) const
|
|
{
|
|
// K is one of tag::x, tag::y, etc.
|
|
}
|
|
};
|
|
|
|
template <typename E, typename Args>
|
|
void check0(E const& e, Args const& args)
|
|
{
|
|
boost::mp11::mp_for_each<E>(some_functor<Args>());
|
|
}
|
|
</pre>
|
|
<p>The first check determines whether or not the argument type of <tt class="docutils literal">_y</tt> is the
|
|
same as the reference type of <tt class="docutils literal">_x</tt>, while the second check determines
|
|
whether or not the argument type of <tt class="docutils literal">_y</tt> is convertible to the value type of
|
|
<tt class="docutils literal">_x</tt>. Here, it's possible to access the reference and value result types of
|
|
indexing an argument pack a little more directly:</p>
|
|
<pre class="literal-block">
|
|
// Use mp_bind on tag::x::binding_fn to access the reference type of _x.
|
|
check<
|
|
<a class="reference internal" href="#parameters"><tt class="docutils literal">parameters</tt></a><
|
|
tag::x
|
|
, <a class="reference internal" href="#optional"><tt class="docutils literal">optional</tt></a><
|
|
<a class="reference internal" href="#deduced"><tt class="docutils literal">deduced</tt></a><tag::y>
|
|
, <a class="reference external" href="../../../mp11/doc/html/mp11.html#mp_bindf_t">boost::mp11::mp_bind</a><
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/types/is_same">std::is_same</a> // <a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_same.html">boost::is_same</a>, standard version.
|
|
, <a class="reference external" href="../../../mp11/doc/html/mp11.html#1_9">boost::mp11::_1</a> // will be bound to the argument type of _y.
|
|
, <a class="reference external" href="../../../mp11/doc/html/mp11.html#mp_bindf_t">boost::mp11::mp_bind</a><
|
|
tag::x::binding_fn
|
|
, <a class="reference external" href="../../../mp11/doc/html/mp11.html#1_9">boost::mp11::_2</a> // will be bound to the argument pack type.
|
|
>
|
|
>
|
|
>
|
|
>
|
|
>((_x = 0, _y = 1), 0, 1);
|
|
|
|
// Use mp_bind_q on tag::x to access the value type of _x.
|
|
check<
|
|
<a class="reference internal" href="#parameters"><tt class="docutils literal">parameters</tt></a><
|
|
tag::x
|
|
, <a class="reference internal" href="#optional"><tt class="docutils literal">optional</tt></a><
|
|
<a class="reference internal" href="#deduced"><tt class="docutils literal">deduced</tt></a><tag::y>
|
|
, <a class="reference external" href="../../../mp11/doc/html/mp11.html#mp_bindf_t">boost::mp11::mp_bind</a><
|
|
<a class="reference external" href="http://en.cppreference.com/w/cpp/types/is_convertible">std::is_convertible</a> // <a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_convertible.html">boost::is_convertible</a>, standard version.
|
|
, <a class="reference external" href="../../../mp11/doc/html/mp11.html#1_9">boost::mp11::_1</a> // will be bound to the argument type of _y.
|
|
, <a class="reference external" href="../../../mp11/doc/html/mp11.html#mp_bind_qq_t">boost::mp11::mp_bind_q</a><
|
|
tag::x
|
|
, <a class="reference external" href="../../../mp11/doc/html/mp11.html#1_9">boost::mp11::_2</a> // will be bound to the argument pack type.
|
|
>
|
|
>
|
|
>
|
|
>
|
|
>((_x = 0U, _y = 1U), 0U, 1U);
|
|
</pre>
|
|
<p>Argument packs still qualify as <a class="reference external" href="../../../mpl/doc/index.html">Boost.MPL</a>-style lists containing
|
|
<a class="reference internal" href="#keyword-tag-type">keyword tag type</a>s:</p>
|
|
<pre class="literal-block">
|
|
template <typename Args>
|
|
struct some_functor
|
|
{
|
|
template <typename K>
|
|
void operator()(K) const
|
|
{
|
|
// K is one of tag::x, tag::y, etc.
|
|
}
|
|
};
|
|
|
|
template <typename E, typename Args>
|
|
void check0(E const& e, Args const& args)
|
|
{
|
|
boost::mpl::for_each<E>(some_functor<Args>());
|
|
}
|
|
</pre>
|
|
<p>However, without <a class="reference external" href="../../../mp11/doc/html/mp11.html">Boost.MP11</a>, the corresponding checks become a little more
|
|
verbose:</p>
|
|
<pre class="literal-block">
|
|
check<
|
|
<a class="reference internal" href="#parameters"><tt class="docutils literal">parameters</tt></a><
|
|
tag::x
|
|
, <a class="reference internal" href="#optional"><tt class="docutils literal">optional</tt></a><
|
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<a class="reference internal" href="#deduced"><tt class="docutils literal">deduced</tt></a><tag::y>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/if.html">mpl::if_</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_same.html">boost::is_same</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/add_lvalue_reference.html">boost::add_lvalue_reference</a><<a class="reference external" href="../../../mp11/doc/html/mp11.html#1_9">boost::mp11::_1</a>>
|
|
, <a class="reference internal" href="#binding"><tt class="docutils literal">binding</tt></a><<a class="reference external" href="../../../mp11/doc/html/mp11.html#1_9">boost::mp11::_2</a>, tag::x>
|
|
>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> // Still have to convert to a
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::false_</a> // <a class="reference external" href="../../../mpl/doc/refmanual/integral-constant.html">Boolean Integral Constant</a>.
|
|
>
|
|
>
|
|
>
|
|
>((_x = 0, _y = 1), 0, 1);
|
|
|
|
// Use tag::x::_ or tag::x::_1 to access the value type of _x.
|
|
check<
|
|
<a class="reference internal" href="#parameters"><tt class="docutils literal">parameters</tt></a><
|
|
tag::x
|
|
, <a class="reference internal" href="#optional"><tt class="docutils literal">optional</tt></a><
|
|
<a class="reference internal" href="#deduced"><tt class="docutils literal">deduced</tt></a><tag::y>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/if.html">mpl::if_</a><
|
|
<a class="reference external" href="../../../type_traits/doc/html/boost_typetraits/is_convertible.html">boost::is_convertible</a><<a class="reference external" href="../../../mp11/doc/html/mp11.html#1_9">boost::mp11::_1</a>, tag::x::_1>
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::true_</a> // Still have to convert to a
|
|
, <a class="reference external" href="../../../mpl/doc/refmanual/bool.html">mpl::false_</a> // <a class="reference external" href="../../../mpl/doc/refmanual/integral-constant.html">Boolean Integral Constant</a>.
|
|
>
|
|
>
|
|
>
|
|
>((_x = 0U, _y = 1U), 0U, 1U);
|
|
</pre>
|
|
<p>The <a class="reference external" href="../../test/singular.cpp">singular.cpp</a>, <a class="reference external" href="../../test/compose.cpp">compose.cpp</a>, <a class="reference external" href="../../test/optional_deduced_sfinae.cpp">optional_deduced_sfinae.cpp</a>, and
|
|
<a class="reference external" href="../../test/deduced_dependent_predicate.cpp">deduced_dependent_predicate.cpp</a> test programs demonstrate proper usage of this
|
|
macro.</p>
|
|
</div>
|
|
<div class="section" id="id24">
|
|
<span id="boost-parameter-disable-mp11-usage"></span><h2><a class="toc-backref" href="#id85">8.4 <tt class="docutils literal">BOOST_PARAMETER_DISABLE_MP11_USAGE</tt></a></h2>
|
|
<p>It may be necessary to disable usage of <a class="reference external" href="../../../mp11/doc/html/mp11.html">Boost.MP11</a> for compilers that
|
|
cannot support it. Users can <tt class="docutils literal">#define</tt> this macro either in their project
|
|
settings or before including any library header files. Doing so will leave
|
|
<a class="reference internal" href="#boost-parameter-can-use-mp11"><tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt></a> undefined.</p>
|
|
</div>
|
|
<div class="section" id="id25">
|
|
<span id="boost-parameter-variadic-mpl-sequence"></span><h2><a class="toc-backref" href="#id86">8.5 <tt class="docutils literal">BOOST_PARAMETER_VARIADIC_MPL_SEQUENCE</tt></a></h2>
|
|
<p>If <a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> is <tt class="docutils literal">#defined</tt>, then determines
|
|
the <a class="reference external" href="../../../mpl/doc/refmanual/variadic-sequence.html">MPL Variadic Sequence</a> underlying the nested <tt class="docutils literal">parameter_spec</tt> type of
|
|
<tt class="docutils literal">parameters</tt>. If the user does not manually <tt class="docutils literal">#define</tt> this macro, then the
|
|
library will <tt class="docutils literal">#define</tt> it as <a class="reference external" href="../../../mp11/doc/html/mp11.html#mp_listt"><tt class="docutils literal"><span class="pre">boost::mp11::mp_list</span></tt></a> if
|
|
<a class="reference internal" href="#boost-parameter-can-use-mp11"><tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt></a> is defined, <a class="reference external" href="../../../fusion/doc/html/fusion/container/list.html"><tt class="docutils literal"><span class="pre">boost::fusion::list</span></tt></a> if
|
|
<a class="reference external" href="../../../../boost/fusion/container/list/list_fwd.hpp"><tt class="docutils literal">BOOST_FUSION_HAS_VARIADIC_LIST</tt></a> is defined (by <a class="reference external" href="../../../fusion/doc/html/index.html">Boost.Fusion</a>),
|
|
<a class="reference external" href="../../../fusion/doc/html/fusion/container/deque.html"><tt class="docutils literal"><span class="pre">boost::fusion::deque</span></tt></a> if <a class="reference external" href="../../../../boost/fusion/container/deque/deque_fwd.hpp"><tt class="docutils literal">BOOST_FUSION_HAS_VARIADIC_DEQUE</tt></a> is defined
|
|
(by <a class="reference external" href="../../../fusion/doc/html/index.html">Boost.Fusion</a>), or <a class="reference external" href="../../../mpl/doc/refmanual/vector.html"><tt class="docutils literal"><span class="pre">boost::mpl::vector</span></tt></a> otherwise.</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">Example:</th><td class="field-body"></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<pre class="literal-block">
|
|
#define BOOST_PARAMETER_VARIADIC_MPL_SEQUENCE <a class="reference external" href="../../../fusion/doc/html/fusion/container/vector.html"><tt class="docutils literal"><span class="pre">boost::fusion::vector</span></tt></a>
|
|
</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">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>
|
|
</div>
|
|
<div class="section" id="id26">
|
|
<span id="boost-parameter-max-arity"></span><h2><a class="toc-backref" href="#id87">8.6 <tt class="docutils literal">BOOST_PARAMETER_MAX_ARITY</tt></a></h2>
|
|
<p>If <a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> is <tt class="docutils literal">#defined</tt>, then:</p>
|
|
<ul class="simple">
|
|
<li>If the <a class="reference external" href="../../../mpl/doc/refmanual/variadic-sequence.html">MPL Variadic Sequence</a> underlying the nested <tt class="docutils literal">parameter_spec</tt>
|
|
type of <tt class="docutils literal">parameters</tt> does not have a size limit--which is the case with
|
|
<a class="reference external" href="../../../mp11/doc/html/mp11.html#mp_listt"><tt class="docutils literal"><span class="pre">boost::mp11::mp_list</span></tt></a>, <a class="reference external" href="../../../fusion/doc/html/fusion/container/list.html"><tt class="docutils literal"><span class="pre">boost::fusion::list</span></tt></a>, and <a class="reference external" href="../../../fusion/doc/html/fusion/container/deque.html"><tt class="docutils literal"><span class="pre">boost::fusion::deque</span></tt></a>, but not
|
|
<a class="reference external" href="../../../mpl/doc/refmanual/vector.html"><tt class="docutils literal"><span class="pre">boost::mpl::vector</span></tt></a>--then this macro can be safely ignored. User code that
|
|
manually defines <a class="reference internal" href="#boost-parameter-variadic-mpl-sequence"><tt class="docutils literal">BOOST_PARAMETER_VARIADIC_MPL_SEQUENCE</tt></a> should also
|
|
manually define this macro to the size limit of the sequence if it has
|
|
one.</li>
|
|
</ul>
|
|
<p>If <a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> is <strong>not</strong> <tt class="docutils literal">#defined</tt>, then:</p>
|
|
<ul class="simple">
|
|
<li>Mutable references must be wrapped by <a class="reference external" href="../../../core/doc/html/core/ref.html"><tt class="docutils literal"><span class="pre">boost::ref</span></tt></a> or <a class="reference external" href="http://en.cppreference.com/w/cpp/utility/functional/ref"><tt class="docutils literal"><span class="pre">std::ref</span></tt></a> if passed
|
|
by position to Boost.Parameter-enabled functions with arity greater than
|
|
or equal to <a class="reference internal" href="#boost-parameter-exponential-overload-threshold-arity"><tt class="docutils literal">BOOST_PARAMETER_EXPONENTIAL_OVERLOAD_THRESHOLD_ARITY</tt></a>.</li>
|
|
</ul>
|
|
<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/config.hpp">boost/parameter/config.hpp</a></td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Default Value:</th><td class="field-body"><a class="reference external" href="../../../mpl/doc/refmanual/limit-vector-size.html"><tt class="docutils literal">BOOST_MPL_LIMIT_VECTOR_SIZE</tt></a> (defined by <a class="reference external" href="../../../mpl/doc/index.html">Boost.MPL</a>) if
|
|
perfect forwarding is supported, <tt class="docutils literal">8</tt> otherwise.</td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Minimum Value:</th><td class="field-body"><tt class="docutils literal">2</tt></td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Maximum Value:</th><td class="field-body"><a class="reference internal" href="#boost-parameter-compose-max-arity"><tt class="docutils literal">BOOST_PARAMETER_COMPOSE_MAX_ARITY</tt></a></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
<div class="section" id="id27">
|
|
<span id="boost-parameter-compose-max-arity"></span><h2><a class="toc-backref" href="#id88">8.7 <tt class="docutils literal">BOOST_PARAMETER_COMPOSE_MAX_ARITY</tt></a></h2>
|
|
<p>If <a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> is <strong>not</strong> <tt class="docutils literal">#defined</tt>, then
|
|
determines the maximum number of arguments supported by the <tt class="docutils literal">compose</tt> function
|
|
and by the <a class="reference internal" href="#boost-parameter-no-spec-function"><tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_FUNCTION</tt></a>,
|
|
<a class="reference internal" href="#boost-parameter-no-spec-member-function"><tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_MEMBER_FUNCTION</tt></a>,
|
|
<a class="reference internal" href="#boost-parameter-no-spec-const-member-function"><tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_CONST_MEMBER_FUNCTION</tt></a>,
|
|
<a class="reference internal" href="#boost-parameter-no-spec-function-call-operator"><tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_FUNCTION_CALL_OPERATOR</tt></a>,
|
|
<a class="reference internal" href="#boost-parameter-no-spec-const-function-call-operator"><tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_CONST_FUNCTION_CALL_OPERATOR</tt></a>,
|
|
<a class="reference internal" href="#boost-parameter-no-spec-constructor"><tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_CONSTRUCTOR</tt></a>, and
|
|
<a class="reference internal" href="#boost-parameter-no-spec-no-base-constructor"><tt class="docutils literal">BOOST_PARAMETER_NO_SPEC_NO_BASE_CONSTRUCTOR</tt></a> code generation macros.</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/config.hpp">boost/parameter/config.hpp</a></td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Default Value:</th><td class="field-body"><tt class="docutils literal">20</tt> for a few older compilers, <tt class="docutils literal">64</tt> otherwise</td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Minimum Value:</th><td class="field-body"><tt class="docutils literal">2</tt></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
</div>
|
|
<div class="section" id="id28">
|
|
<span id="boost-parameter-exponential-overload-threshold-arity"></span><h2><a class="toc-backref" href="#id89">8.8 <tt class="docutils literal">BOOST_PARAMETER_EXPONENTIAL_OVERLOAD_THRESHOLD_ARITY</tt></a></h2>
|
|
<p>If this library does <strong>not</strong> support perfect forwarding, determines the number
|
|
of arguments less than which <tt class="docutils literal">parameters</tt> generates an exponential number of
|
|
function call operator overloads, and greater than or equal to which
|
|
<tt class="docutils literal">parameters</tt> does not. Will only be <tt class="docutils literal">#defined</tt> by the library if it is
|
|
not already <tt class="docutils literal">#defined</tt> and <a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> is
|
|
<strong>not</strong> <tt class="docutils literal">#defined</tt>.</p>
|
|
<table class="docutils field-list" frame="void" rules="none">
|
|
<col class="field-name" />
|
|
<col class="field-body" />
|
|
<tbody valign="top">
|
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<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference external" href="../../../../boost/parameter/config.hpp">boost/parameter/config.hpp</a></td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Default Value:</th><td class="field-body"><tt class="docutils literal">0</tt></td>
|
|
</tr>
|
|
<tr class="field"><th class="field-name">Minimum Value:</th><td class="field-body"><tt class="docutils literal">0</tt></td>
|
|
</tr>
|
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</tbody>
|
|
</table>
|
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</div>
|
|
<div class="section" id="outside-of-this-library">
|
|
<h2><a class="toc-backref" href="#id90">8.9 ...Outside Of This Library</a></h2>
|
|
<ol class="arabic simple">
|
|
<li>If <a class="reference external" href="../../../config/doc/html/index.html">Boost.Config</a> defines the macro
|
|
<a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__03_defects"><tt class="docutils literal">BOOST_NO_FUNCTION_TEMPLATE_ORDERING</tt></a>, then the macros
|
|
<a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> and
|
|
<a class="reference internal" href="#boost-parameter-can-use-mp11"><tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt></a> will be left undefined; otherwise, the
|
|
code generation macros would not work correctly.</li>
|
|
<li>If <a class="reference external" href="../../../config/doc/html/index.html">Boost.Config</a> defines the macro <a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__03_defects"><tt class="docutils literal">BOOST_NO_SFINAE</tt></a>, then the macros
|
|
<a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> and
|
|
<a class="reference internal" href="#boost-parameter-can-use-mp11"><tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt></a> will be left undefined; otherwise, keyword
|
|
types generated by <a class="reference internal" href="#boost-parameter-name"><tt class="docutils literal">BOOST_PARAMETER_NAME</tt></a> and
|
|
<a class="reference internal" href="#boost-parameter-nested-keyword"><tt class="docutils literal">BOOST_PARAMETER_NESTED_KEYWORD</tt></a> would not work correctly.</li>
|
|
<li>If <a class="reference external" href="../../../config/doc/html/index.html">Boost.Config</a> defines the macro
|
|
<a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__11_features_not_supported"><tt class="docutils literal">BOOST_NO_CXX11_RVALUE_REFERENCES</tt></a>, then the macros
|
|
<a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> and
|
|
<a class="reference internal" href="#boost-parameter-can-use-mp11"><tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt></a> will be left undefined.</li>
|
|
<li>If <a class="reference external" href="../../../config/doc/html/index.html">Boost.Config</a> defines the macro <a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__11_features_not_supported"><tt class="docutils literal">BOOST_NO_CXX11_VARIADIC_TEMPLATES</tt></a>,
|
|
then the macros <a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> and
|
|
<a class="reference internal" href="#boost-parameter-can-use-mp11"><tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt></a> will be left undefined.</li>
|
|
<li>If <a class="reference external" href="../../../config/doc/html/index.html">Boost.Config</a> defines the macro
|
|
<a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__11_features_not_supported"><tt class="docutils literal">BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS</tt></a>, then the macros
|
|
<a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a> and
|
|
<a class="reference internal" href="#boost-parameter-can-use-mp11"><tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt></a> will be left undefined.</li>
|
|
<li>If <a class="reference external" href="../../../config/doc/html/index.html">Boost.Config</a> defines the macro <a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__11_features_not_supported"><tt class="docutils literal">BOOST_NO_CXX11_CONSTEXPR</tt></a>, then the
|
|
macro <a class="reference internal" href="#boost-parameter-can-use-mp11"><tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt></a> will be left undefined.</li>
|
|
<li>If <a class="reference external" href="../../../config/doc/html/index.html">Boost.Config</a> defines the macro <a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__11_features_not_supported"><tt class="docutils literal">BOOST_NO_CXX11_DECLTYPE_N3276</tt></a>,
|
|
then the macro <a class="reference internal" href="#boost-parameter-can-use-mp11"><tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt></a> will be left undefined.</li>
|
|
<li>If <a class="reference external" href="../../../config/doc/html/index.html">Boost.Config</a> defines the macro <a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__11_features_not_supported"><tt class="docutils literal">BOOST_NO_CXX11_AUTO_DECLARATIONS</tt></a>,
|
|
then the macro <a class="reference internal" href="#boost-parameter-can-use-mp11"><tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt></a> will be left undefined.</li>
|
|
<li>If <a class="reference external" href="../../../config/doc/html/index.html">Boost.Config</a> defines the macro <a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__11_features_not_supported"><tt class="docutils literal">BOOST_NO_CXX11_TEMPLATE_ALIASES</tt></a>,
|
|
then the macro <a class="reference internal" href="#boost-parameter-can-use-mp11"><tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt></a> will be left undefined.</li>
|
|
<li>If <a class="reference external" href="../../../config/doc/html/index.html">Boost.Config</a> defines the macro <a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__11_features_not_supported"><tt class="docutils literal">BOOST_NO_CXX11_STATIC_ASSERT</tt></a>, then
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the macro <a class="reference internal" href="#boost-parameter-can-use-mp11"><tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt></a> will be left undefined.</li>
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<li>If <a class="reference external" href="../../../config/doc/html/index.html">Boost.Config</a> defines the macro <a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__11_features_not_supported"><tt class="docutils literal">BOOST_NO_CXX11_HDR_TYPE_TRAITS</tt></a>,
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then the macro <a class="reference internal" href="#boost-parameter-can-use-mp11"><tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt></a> will be left undefined.</li>
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<li>If <a class="reference external" href="../../../config/doc/html/index.html">Boost.Config</a> defines the macro
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<a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__11_features_not_supported"><tt class="docutils literal">BOOST_NO_CXX11_HDR_INITIALIZER_LIST</tt></a>, then the macro
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<a class="reference internal" href="#boost-parameter-can-use-mp11"><tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt></a> will be left undefined.</li>
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<li>If <a class="reference external" href="../../../config/doc/html/index.html">Boost.Config</a> defines the macro <a class="reference external" href="../../../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.macros_that_describe_c__11_features_not_supported"><tt class="docutils literal">BOOST_NO_CXX11_HDR_TUPLE</tt></a>, then the
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macro <a class="reference internal" href="#boost-parameter-can-use-mp11"><tt class="docutils literal">BOOST_PARAMETER_CAN_USE_MP11</tt></a> will be left undefined.</li>
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<li>If <a class="reference external" href="../../../fusion/doc/html/index.html">Boost.Fusion</a> defines the macro <a class="reference external" href="../../../../boost/fusion/container/list/list_fwd.hpp"><tt class="docutils literal">BOOST_FUSION_HAS_VARIADIC_LIST</tt></a>,
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if this library defines the macro
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<a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a>, and if
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<a class="reference internal" href="#boost-parameter-variadic-mpl-sequence"><tt class="docutils literal">BOOST_PARAMETER_VARIADIC_MPL_SEQUENCE</tt></a> is left undefined, then the
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<a class="reference external" href="../../../mpl/doc/refmanual/variadic-sequence.html">MPL Variadic Sequence</a> underlying the nested <tt class="docutils literal">parameter_spec</tt> type of
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<tt class="docutils literal">parameters</tt> will be <a class="reference external" href="../../../fusion/doc/html/fusion/container/list.html"><tt class="docutils literal"><span class="pre">boost::fusion::list</span></tt></a>.</li>
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<li>If <a class="reference external" href="../../../fusion/doc/html/index.html">Boost.Fusion</a> defines the macro <a class="reference external" href="../../../../boost/fusion/container/deque/deque_fwd.hpp"><tt class="docutils literal">BOOST_FUSION_HAS_VARIADIC_DEQUE</tt></a>,
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if this library defines the macro
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<a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a>, and if
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<a class="reference internal" href="#boost-parameter-variadic-mpl-sequence"><tt class="docutils literal">BOOST_PARAMETER_VARIADIC_MPL_SEQUENCE</tt></a> is left undefined, then the
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<a class="reference external" href="../../../mpl/doc/refmanual/variadic-sequence.html">MPL Variadic Sequence</a> underlying the nested <tt class="docutils literal">parameter_spec</tt> type of
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<tt class="docutils literal">parameters</tt> will be <a class="reference external" href="../../../fusion/doc/html/fusion/container/deque.html"><tt class="docutils literal"><span class="pre">boost::fusion::deque</span></tt></a>.</li>
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<li>The value that <a class="reference external" href="../../../mpl/doc/index.html">Boost.MPL</a> defines the macro
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<a class="reference external" href="../../../mpl/doc/refmanual/limit-vector-size.html"><tt class="docutils literal">BOOST_MPL_LIMIT_VECTOR_SIZE</tt></a> as will be the value that this library
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defines the macro <a class="reference internal" href="#boost-parameter-max-arity"><tt class="docutils literal">BOOST_PARAMETER_MAX_ARITY</tt></a> as if this library defines
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the macro <a class="reference internal" href="#boost-parameter-has-perfect-forwarding"><tt class="docutils literal">BOOST_PARAMETER_HAS_PERFECT_FORWARDING</tt></a>.</li>
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</ol>
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</div>
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</div>
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<div class="section" id="tutorial">
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<h1><a class="toc-backref" href="#id91">9 Tutorial</a></h1>
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<p>Follow <a class="reference external" href="index.html#tutorial">this link</a> to the Boost.Parameter tutorial documentation.</p>
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<hr class="docutils" />
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<table class="docutils footnote" frame="void" id="thread" rules="none">
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<colgroup><col class="label" /><col /></colgroup>
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<tbody valign="top">
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<tr><td class="label"><a class="fn-backref" href="#id2">[1]</a></td><td>References to tag objects may be initialized multiple
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times. This scenario can only occur in the presence of
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threading. Because the C++ standard doesn't consider threading,
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it doesn't explicitly allow or forbid multiple initialization of
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references. That said, it's hard to imagine an implementation
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where it could make a difference.</td></tr>
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</tbody>
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</table>
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<table class="docutils footnote" frame="void" id="no-result-of" rules="none">
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<colgroup><col class="label" /><col /></colgroup>
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<tbody valign="top">
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<tr><td class="label">[2]</td><td><em>(<a class="fn-backref" href="#id6">1</a>, <a class="fn-backref" href="#id12">2</a>, <a class="fn-backref" href="#id15">3</a>)</em> Where <a class="reference external" href="../../../utility/utility.htm#BOOST_NO_RESULT_OF"><tt class="docutils literal">BOOST_NO_RESULT_OF</tt></a> is <tt class="docutils literal">#defined</tt>,
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<a class="reference external" href="../../../utility/utility.htm#result_of"><tt class="docutils literal"><span class="pre">boost::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>
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</tbody>
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</table>
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</div>
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<div class="footer">
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<hr class="footer" />
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Generated on: 2019-09-04 02:34 UTC.
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Generated by <a class="reference external" href="http://docutils.sourceforge.net/">Docutils</a> from <a class="reference external" href="http://docutils.sourceforge.net/rst.html">reStructuredText</a> source.
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