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6<meta name="generator" content="Docutils 0.5: http://docutils.sourceforge.net/" />
7<title>The Boost Parameter Library Reference Documentation</title>
8<meta name="authors" content="David Abrahams  Daniel Wallin" />
9<meta name="organization" content="Boost Consulting" />
10<meta name="date" content="2005-07-17" />
11<meta name="copyright" content="Copyright David Abrahams, Daniel Wallin 2005. Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)" />
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14<body>
15<div class="document" id="the-boost-parameter-library-reference-documentation">
16<h1 class="title">The Boost Parameter Library Reference Documentation</h1>
17<table class="docinfo" frame="void" rules="none">
18<col class="docinfo-name" />
19<col class="docinfo-content" />
20<tbody valign="top">
21<tr><th class="docinfo-name">Authors:</th>
22<td>David Abrahams
23<br />Daniel Wallin</td></tr>
24<tr><th class="docinfo-name">Contact:</th>
25<td><a class="first reference" href="mailto:dave&#64;boost-consulting.com">dave&#64;boost-consulting.com</a>, <a class="last reference" href="mailto:dalwan01&#64;student.umu.se">dalwan01&#64;student.umu.se</a></td></tr>
26<tr><th class="docinfo-name">Organization:</th>
27<td><a class="first last reference" href="http://www.boost-consulting.com">Boost Consulting</a></td></tr>
28<tr><th class="docinfo-name">Date:</th>
29<td>2005-07-17</td></tr>
30<tr><th class="docinfo-name">Copyright:</th>
31<td>Copyright David Abrahams, Daniel Wallin
322005. Distributed under the Boost Software License,
33Version 1.0. (See accompanying file LICENSE_1_0.txt
34or copy at <a class="reference" href="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</a>)</td></tr>
35</tbody>
36</table>
37<p><a class="reference" href="../../../../index.htm"><img alt="Boost" src="../../../../boost.png" /></a></p>
38<hr class="docutils" />
39<div class="contents topic">
40<p class="topic-title first"><a id="contents" name="contents">Contents</a></p>
41<ul class="auto-toc simple">
42<li><a class="reference" href="#preliminaries" id="id30" name="id30">1&nbsp;&nbsp;&nbsp;Preliminaries</a><ul class="auto-toc">
43<li><a class="reference" href="#namespaces" id="id31" name="id31">1.1&nbsp;&nbsp;&nbsp;Namespaces</a></li>
44<li><a class="reference" href="#exceptions" id="id32" name="id32">1.2&nbsp;&nbsp;&nbsp;Exceptions</a></li>
45<li><a class="reference" href="#thread-safety" id="id33" name="id33">1.3&nbsp;&nbsp;&nbsp;Thread Safety</a></li>
46<li><a class="reference" href="#typography" id="id34" name="id34">1.4&nbsp;&nbsp;&nbsp;Typography</a></li>
47</ul>
48</li>
49<li><a class="reference" href="#terminology" id="id35" name="id35">2&nbsp;&nbsp;&nbsp;Terminology</a></li>
50<li><a class="reference" href="#concepts" id="id36" name="id36">3&nbsp;&nbsp;&nbsp;Concepts</a><ul class="auto-toc">
51<li><a class="reference" href="#argumentpack" id="id37" name="id37">3.1&nbsp;&nbsp;&nbsp;<span class="concept">ArgumentPack</span></a></li>
52<li><a class="reference" href="#id5" id="id38" name="id38">3.2&nbsp;&nbsp;&nbsp;<span class="concept">ParameterSpec</span></a></li>
53</ul>
54</li>
55<li><a class="reference" href="#class-templates" id="id39" name="id39">4&nbsp;&nbsp;&nbsp;Class Templates</a><ul class="auto-toc">
56<li><a class="reference" href="#id7" id="id40" name="id40">4.1&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">keyword</span></tt></a></li>
57<li><a class="reference" href="#parameters" id="id41" name="id41">4.2&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">parameters</span></tt></a></li>
58<li><a class="reference" href="#optional-required" id="id42" name="id42">4.3&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">optional</span></tt>, <tt class="docutils literal"><span class="pre">required</span></tt></a></li>
59<li><a class="reference" href="#deduced" id="id43" name="id43">4.4&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">deduced</span></tt></a></li>
60</ul>
61</li>
62<li><a class="reference" href="#metafunctions" id="id44" name="id44">5&nbsp;&nbsp;&nbsp;Metafunctions</a><ul class="auto-toc">
63<li><a class="reference" href="#binding" id="id45" name="id45">5.1&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">binding</span></tt></a></li>
64<li><a class="reference" href="#lazy-binding" id="id46" name="id46">5.2&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">lazy_binding</span></tt></a></li>
65<li><a class="reference" href="#value-type" id="id47" name="id47">5.3&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">value_type</span></tt></a></li>
66</ul>
67</li>
68<li><a class="reference" href="#code-generation-macros" id="id48" name="id48">6&nbsp;&nbsp;&nbsp;Code Generation Macros</a><ul class="auto-toc">
69<li><a class="reference" href="#boost-parameter-function-result-name-tag-namespace-arguments" id="id49" name="id49">6.1&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_FUNCTION(result,name,tag_namespace,arguments)</span></tt></a></li>
70<li><a class="reference" href="#boost-parameter-member-function-result-name-tag-namespace-arguments" id="id50" name="id50">6.2&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_MEMBER_FUNCTION(result,name,tag_namespace,arguments)</span></tt></a></li>
71<li><a class="reference" href="#boost-parameter-constructor-cls-impl-tag-namespace-arguments" id="id51" name="id51">6.3&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_CONSTRUCTOR(cls,</span> <span class="pre">impl,</span> <span class="pre">tag_namespace,</span> <span class="pre">arguments)</span></tt></a></li>
72<li><a class="reference" href="#boost-parameter-name-name" id="id52" name="id52">6.4&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_NAME(name)</span></tt></a></li>
73<li><a class="reference" href="#boost-parameter-template-keyword-name" id="id53" name="id53">6.5&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_TEMPLATE_KEYWORD(name)</span></tt></a></li>
74<li><a class="reference" href="#boost-parameter-fun-r-n-l-h-p" id="id54" name="id54">6.6&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_FUN(r,n,l,h,p)</span></tt></a></li>
75<li><a class="reference" href="#boost-parameter-keyword-n-k" id="id55" name="id55">6.7&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_KEYWORD(n,k)</span></tt></a></li>
76<li><a class="reference" href="#boost-parameter-match-p-a-x" id="id56" name="id56">6.8&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_MATCH(p,a,x)</span></tt></a></li>
77</ul>
78</li>
79<li><a class="reference" href="#configuration-macros" id="id57" name="id57">7&nbsp;&nbsp;&nbsp;Configuration Macros</a><ul class="auto-toc">
80<li><a class="reference" href="#boost-parameter-max-arity" id="id58" name="id58">7.1&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_MAX_ARITY</span></tt></a></li>
81</ul>
82</li>
83<li><a class="reference" href="#tutorial" id="id59" name="id59">8&nbsp;&nbsp;&nbsp;Tutorial</a></li>
84</ul>
85</div>
86<hr class="docutils" />
87<div class="section">
88<h1><a class="toc-backref" href="#id30" id="preliminaries" name="preliminaries">1&nbsp;&nbsp;&nbsp;Preliminaries</a></h1>
89<p>This section covers some basic information you'll need to know in
90order to understand this reference</p>
91<div class="section">
92<h2><a class="toc-backref" href="#id31" id="namespaces" name="namespaces">1.1&nbsp;&nbsp;&nbsp;Namespaces</a></h2>
93<p>In this document, all unqualified identifiers should be assumed to
94be defined in namespace <tt class="docutils literal"><span class="pre">boost::parameter</span></tt> unless otherwise
95specified.</p>
96</div>
97<div class="section">
98<h2><a class="toc-backref" href="#id32" id="exceptions" name="exceptions">1.2&nbsp;&nbsp;&nbsp;Exceptions</a></h2>
99<p>No operation described in this document
100throws an exception unless otherwise specified.</p>
101</div>
102<div class="section">
103<h2><a class="toc-backref" href="#id33" id="thread-safety" name="thread-safety">1.3&nbsp;&nbsp;&nbsp;Thread Safety</a></h2>
104<p>All components of this library can be used safely from multiple
105threads without synchronization.<a class="footnote-reference" href="#thread" id="id2" name="id2"><sup>1</sup></a></p>
106</div>
107<div class="section">
108<h2><a class="toc-backref" href="#id34" id="typography" name="typography">1.4&nbsp;&nbsp;&nbsp;Typography</a></h2>
109<p>Names written in <span class="concept">sans serif type</span> represent <a class="reference" href="../../../../more/generic_programming.html#concept">concepts</a>.</p>
110<p>In code blocks, <em>italic type</em> represents unspecified text that
111satisfies the requirements given in the detailed description that
112follows the code block.</p>
113<p>In a specification of the tokens generated by a macro, <strong>bold
114type</strong> is used to highlight the position of the expanded macro
115argument in the result.</p>
116<p>The special character β represents the value of <a class="reference" href="#boost-parameter-max-arity"><tt class="docutils literal"><span class="pre">BOOST_PARAMETER_MAX_ARITY</span></tt></a>.</p>
117</div>
118</div>
119<hr class="docutils" />
120<div class="section">
121<h1><a class="toc-backref" href="#id35" id="terminology" name="terminology">2&nbsp;&nbsp;&nbsp;Terminology</a></h1>
122<dl class="docutils" id="kw">
123<dt>keyword</dt>
124<dd>The name of a function parameter.</dd>
125</dl>
126<span class="target" id="keyword-tag-type"></span><dl class="docutils">
127<dt>keyword tag type</dt>
128<dd>A type used to uniquely identify a function parameter.  Typically
129its name will be the same as that of the parameter.</dd>
130</dl>
131<span class="target" id="positional"></span><dl class="docutils">
132<dt>positional argument</dt>
133<dd>An argument passed with no explicit keyword.  Its parameter is
134determined in the usual C++ way: by position with respect to a
135parameter list.</dd>
136</dl>
137<span class="target" id="tag-type"></span><dl class="docutils">
138<dt>tag type</dt>
139<dd>Shorthand for “<a class="reference" href="#keyword-tag-type">keyword tag type</a>.”</dd>
140</dl>
141<span class="target" id="keyword-object"></span><dl class="docutils">
142<dt>keyword object</dt>
143<dd>An instance of <a class="reference" href="#keyword"><tt class="docutils literal"><span class="pre">keyword</span></tt></a> <tt class="docutils literal"><span class="pre">&lt;T&gt;</span></tt> for some <a class="reference" href="#tag-type">tag type</a> <tt class="docutils literal"><span class="pre">T</span></tt>.</dd>
144</dl>
145<span class="target" id="tagged-reference"></span><dl class="docutils">
146<dt>tagged reference</dt>
147<dd><p class="first">An object whose type is associated with a <a class="reference" href="#keyword-tag-type">keyword tag type</a> (the
148object's <em>keyword</em>), and that holds a reference (to the object's
149<em>value</em>).</p>
150<p class="last">As a shorthand, a “tagged reference to <tt class="docutils literal"><span class="pre">x</span></tt>” means a tagged
151reference whose <em>value</em> is <tt class="docutils literal"><span class="pre">x</span></tt>.</p>
152</dd>
153</dl>
154<span class="target" id="tagged-default"></span><dl class="docutils">
155<dt>tagged default</dt>
156<dd>A <a class="reference" href="#tagged-reference">tagged reference</a> whose <em>value</em> represents the value of a
157default argument.</dd>
158</dl>
159<span class="target" id="tagged-lazy-default"></span><dl class="docutils">
160<dt>tagged lazy default</dt>
161<dd>A <a class="reference" href="#tagged-reference">tagged reference</a> whose <em>value</em>, when invoked with no
162arguments, computes a default argument value.</dd>
163</dl>
164<span class="target" id="intended-argument-type"></span><dl class="docutils">
165<dt>intended argument type</dt>
166<dd>The <em>intended argument type</em> of a single-element <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> is the
167type of its element's <em>value</em>.  The intended argument type of any other
168type <tt class="docutils literal"><span class="pre">X</span></tt> is <tt class="docutils literal"><span class="pre">X</span></tt> itself.</dd>
169</dl>
170<div class="note">
171<p class="first admonition-title">Note</p>
172<p class="last">In this reference, we will use concept names (and other names)
173to describe both types and objects, depending on context.  So
174for example, “an <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a>” can refer to a type that
175models <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> <em>or</em> an object of such a type.</p>
176</div>
177</div>
178<hr class="docutils" />
179<div class="section">
180<h1><a class="toc-backref" href="#id36" id="concepts" name="concepts">3&nbsp;&nbsp;&nbsp;Concepts</a></h1>
181<p>This section describes the generic type <a class="reference" href="../../../../more/generic_programming.html#concept">concepts</a> used by the Parameter library.</p>
182<div class="section">
183<h2><a class="toc-backref" href="#id37" id="argumentpack" name="argumentpack">3.1&nbsp;&nbsp;&nbsp;<span class="concept">ArgumentPack</span></a></h2>
184<p>An <span class="concept">ArgumentPack</span> is a collection of <a class="reference" href="#tagged-reference">tagged reference</a>s to the
185actual arguments passed to a function.  Every <span class="concept">ArgumentPack</span> is
186also a valid MPL <a class="reference" href="../../../mpl/doc/refmanual/forward-sequence.html"><span class="concept">Forward Sequence</span></a> consisting of the <a class="reference" href="#keyword-tag-type">keyword tag type</a>s in its <a class="reference" href="#tagged-reference">tagged reference</a>s.</p>
187<div class="section">
188<h3><a id="requirements" name="requirements">Requirements</a></h3>
189<p>In the table below,</p>
190<ul class="simple">
191<li><tt class="docutils literal"><span class="pre">A</span></tt> is a model of <span class="concept">ArgumentPack</span></li>
192<li><tt class="docutils literal"><span class="pre">x</span></tt> is an instance of <tt class="docutils literal"><span class="pre">A</span></tt></li>
193<li><tt class="docutils literal"><span class="pre">u</span></tt> is a <a class="reference" href="#keyword-object">keyword object</a> of type <tt class="docutils literal"><span class="pre">K</span></tt></li>
194<li><tt class="docutils literal"><span class="pre">v</span></tt> is a <a class="reference" href="#tagged-default">tagged default</a> with <a class="reference" href="#tag-type">tag type</a> <tt class="docutils literal"><span class="pre">L</span></tt> and <em>value</em> of type <tt class="docutils literal"><span class="pre">D</span></tt></li>
195<li><tt class="docutils literal"><span class="pre">w</span></tt> is a <a class="reference" href="#tagged-lazy-default">tagged lazy default</a> with <a class="reference" href="#tag-type">tag type</a> <tt class="docutils literal"><span class="pre">M</span></tt> and <em>value</em> of type <tt class="docutils literal"><span class="pre">E</span> <span class="pre">const</span></tt></li>
196<li><tt class="docutils literal"><span class="pre">z</span></tt> is an <span class="concept">ArgumentPack</span> containing a single element (as created by <a class="reference" href="#keyword"><tt class="docutils literal"><span class="pre">keyword</span></tt></a><tt class="docutils literal"><span class="pre">&lt;…&gt;::operator=</span></tt>)</li>
197</ul>
198<p>Any exceptions are thrown from the invocation of <tt class="docutils literal"><span class="pre">w</span></tt>'s <em>value</em>
199will be propagated to the caller.</p>
200<table border="1" class="docutils">
201<caption><span class="concept">ArgumentPack</span> requirements</caption>
202<colgroup>
203<col width="11%" />
204<col width="31%" />
205<col width="19%" />
206<col width="40%" />
207</colgroup>
208<thead valign="bottom">
209<tr><th class="head">Expression</th>
210<th class="head">Type</th>
211<th class="head">Requirements</th>
212<th class="head">Semantics/Notes</th>
213</tr>
214</thead>
215<tbody valign="top">
216<tr><td><tt class="docutils literal"><span class="pre">x[u]</span></tt></td>
217<td><tt class="docutils literal"><span class="pre">binding&lt;A,K&gt;::type</span></tt></td>
218<td><tt class="docutils literal"><span class="pre">x</span></tt> contains an
219element <em>b</em> whose
220<a class="reference" href="#kw">keyword</a> is <tt class="docutils literal"><span class="pre">K</span></tt></td>
221<td>Returns <em>b</em>'s <em>value</em> (by
222reference).</td>
223</tr>
224<tr><td><tt class="docutils literal"><span class="pre">x[u]</span></tt></td>
225<td><tt class="docutils literal"><span class="pre">binding&lt;A,L,D&gt;::type</span></tt></td>
226<td><em>none</em></td>
227<td>If <tt class="docutils literal"><span class="pre">x</span></tt> contains an element <em>b</em> whose
228<a class="reference" href="#kw">keyword</a> is the same as <tt class="docutils literal"><span class="pre">u</span></tt>'s,
229returns <em>b</em>'s <em>value</em> (by
230reference).  Otherwise, returns <tt class="docutils literal"><span class="pre">u</span></tt>'s <em>value</em>.</td>
231</tr>
232<tr><td><tt class="docutils literal"><span class="pre">x[w]</span></tt></td>
233<td><tt class="docutils literal"><span class="pre">lazy_binding&lt;A,M,E&gt;::type</span></tt></td>
234<td><em>none</em></td>
235<td>If <tt class="docutils literal"><span class="pre">x</span></tt> contains an element <em>b</em> whose
236<a class="reference" href="#kw">keyword</a> is the same as <tt class="docutils literal"><span class="pre">w</span></tt>'s,
237returns <em>b</em>'s <em>value</em> (by
238reference).  Otherwise, invokes <tt class="docutils literal"><span class="pre">w</span></tt>'s <em>value</em> and returns the result.</td>
239</tr>
240<tr><td><tt class="docutils literal"><span class="pre">x,</span> <span class="pre">z</span></tt></td>
241<td>Model of <span class="concept">ArgumentPack</span></td>
242<td><em>none</em></td>
243<td>Returns an <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> containing
244all the elements of both <tt class="docutils literal"><span class="pre">x</span></tt> and
245<tt class="docutils literal"><span class="pre">z</span></tt>.</td>
246</tr>
247</tbody>
248</table>
249</div>
250</div>
251<div class="section">
252<h2><a class="toc-backref" href="#id38" id="id5" name="id5"><span id="parameterspec"></span>3.2&nbsp;&nbsp;&nbsp;<span class="concept">ParameterSpec</span></a></h2>
253<p>A <span class="concept">ParameterSpec</span> describes the type requirements for arguments
254corresponding to a given <a class="reference" href="#kw">keyword</a> and indicates whether the argument
255is optional or required.  The table below details the allowed forms
256and describes their condition for satisfaction by an actual
257argument type. In each row,</p>
258<ul class="simple" id="conditions">
259<li><tt class="docutils literal"><span class="pre">K</span></tt> is the <span class="concept">ParameterSpec</span>'s <a class="reference" href="#keyword-tag-type">keyword tag type</a></li>
260<li><tt class="docutils literal"><span class="pre">A</span></tt> is an <a class="reference" href="#intended-argument-type">intended argument type</a> associated with <tt class="docutils literal"><span class="pre">K</span></tt>, if any</li>
261<li><tt class="docutils literal"><span class="pre">F</span></tt> is a unary <a class="reference" href="../../../mpl/doc/refmanual/lambda-expression.html">MPL lambda expression</a></li>
262</ul>
263<table border="1" class="docutils">
264<caption><span class="concept">ParameterSpec</span> allowed forms and conditions of satisfaction</caption>
265<colgroup>
266<col width="32%" />
267<col width="21%" />
268<col width="47%" />
269</colgroup>
270<thead valign="bottom">
271<tr><th class="head">Type</th>
272<th class="head"><tt class="docutils literal"><span class="pre">A</span></tt> required</th>
273<th class="head">Condition <tt class="docutils literal"><span class="pre">A</span></tt> must satisfy</th>
274</tr>
275</thead>
276<tbody valign="top">
277<tr><td><tt class="docutils literal"><span class="pre">K</span></tt></td>
278<td>no</td>
279<td><em>n/a</em></td>
280</tr>
281<tr><td><a class="reference" href="#optional"><tt class="docutils literal"><span class="pre">optional</span></tt></a><tt class="docutils literal"><span class="pre">&lt;K,F&gt;</span></tt></td>
282<td>no</td>
283<td><tt class="docutils literal"><span class="pre">mpl::apply&lt;F,A&gt;::type::value</span></tt>
284is <tt class="docutils literal"><span class="pre">true</span></tt>.</td>
285</tr>
286<tr><td><a class="reference" href="#required"><tt class="docutils literal"><span class="pre">required</span></tt></a><tt class="docutils literal"><span class="pre">&lt;K,F&gt;</span></tt></td>
287<td>yes</td>
288<td><tt class="docutils literal"><span class="pre">mpl::apply&lt;F,A&gt;::type::value</span></tt>
289is <tt class="docutils literal"><span class="pre">true</span></tt>.</td>
290</tr>
291</tbody>
292</table>
293<p>The information in a <span class="concept">ParameterSpec</span> is used to <a class="reference" href="index.html#controlling-overload-resolution">limit</a> the
294arguments that will be matched by <a class="reference" href="index.html#forwarding-functions">forwarding functions</a>.</p>
295</div>
296</div>
297<hr class="docutils" />
298<div class="section">
299<h1><a class="toc-backref" href="#id39" id="class-templates" name="class-templates">4&nbsp;&nbsp;&nbsp;Class Templates</a></h1>
300<div class="section">
301<h2><a class="toc-backref" href="#id40" id="id7" name="id7"><span id="keyword"></span>4.1&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">keyword</span></tt></a></h2>
302<p>The type of every <a class="reference" href="#keyword-object">keyword object</a> is a specialization of <tt class="docutils literal"><span class="pre">keyword</span></tt>.</p>
303<table class="docutils field-list" frame="void" rules="none">
304<col class="field-name" />
305<col class="field-body" />
306<tbody valign="top">
307<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/keyword.hpp">boost/parameter/keyword.hpp</a></td>
308</tr>
309</tbody>
310</table>
311<pre class="literal-block">
312template &lt;class Tag&gt;
313struct keyword
314{
315    template &lt;class T&gt; <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> <a class="reference" href="#operator">operator=</a>(T&amp; value) const;
316    template &lt;class T&gt; <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> <a class="reference" href="#operator">operator=</a>(T const&amp; value) const;
317
318    template &lt;class T&gt; <em>tagged default</em> <a class="reference" href="#id9">operator|</a>(T&amp; x) const;
319    template &lt;class T&gt; <em>tagged default</em> <a class="reference" href="#id9">operator|</a>(T const&amp; x) const;
320
321    template &lt;class F&gt; <em>tagged lazy default</em> <a class="reference" href="#id10">operator||</a>(F const&amp;) const;
322
323    static keyword&lt;Tag&gt;&amp; <a class="reference" href="#get">get</a>();
324};
325</pre>
326<dl class="docutils" id="operator">
327<dt><tt class="docutils literal"><span class="pre">operator=</span></tt></dt>
328<dd><pre class="first literal-block">
329template &lt;class T&gt; <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> operator=(T&amp; value) const;
330template &lt;class T&gt; <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> operator=(T const&amp; value) const;
331</pre>
332<table class="last docutils field-list" frame="void" rules="none">
333<col class="field-name" />
334<col class="field-body" />
335<tbody valign="top">
336<tr class="field"><th class="field-name">Requires:</th><td class="field-body">nothing</td>
337</tr>
338<tr class="field"><th class="field-name">Returns:</th><td class="field-body">an <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a>  containing a single <a class="reference" href="#tagged-reference">tagged reference</a> to
339<tt class="docutils literal"><span class="pre">value</span></tt> with <a class="reference" href="#kw">keyword</a> <tt class="docutils literal"><span class="pre">Tag</span></tt></td>
340</tr>
341</tbody>
342</table>
343</dd>
344</dl>
345<dl class="docutils" id="id9">
346<dt><tt class="docutils literal"><span class="pre">operator|</span></tt></dt>
347<dd><pre class="first literal-block">
348template &lt;class T&gt; <em>tagged default</em> operator|(T&amp; x) const;
349template &lt;class T&gt; <em>tagged default</em> operator|(T const&amp; x) const;
350</pre>
351<table class="last docutils field-list" frame="void" rules="none">
352<col class="field-name" />
353<col class="field-body" />
354<tbody valign="top">
355<tr class="field"><th class="field-name">Returns:</th><td class="field-body">a <a class="reference" href="#tagged-default">tagged default</a> with <em>value</em> <tt class="docutils literal"><span class="pre">x</span></tt> and <a class="reference" href="#kw">keyword</a> <tt class="docutils literal"><span class="pre">Tag</span></tt>.</td>
356</tr>
357</tbody>
358</table>
359</dd>
360</dl>
361<dl class="docutils" id="id10">
362<dt><tt class="docutils literal"><span class="pre">operator||</span></tt></dt>
363<dd><pre class="first literal-block">
364template &lt;class F&gt; <em>tagged lazy default</em> operator||(F const&amp; g) const;
365</pre>
366<table class="last docutils field-list" frame="void" rules="none">
367<col class="field-name" />
368<col class="field-body" />
369<tbody valign="top">
370<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><tt class="docutils literal"><span class="pre">g()</span></tt> is valid, with type <tt class="docutils literal"><span class="pre">boost::</span></tt><a class="reference" href="../../../utility/utility.htm#result_of"><tt class="docutils literal"><span class="pre">result_of</span></tt></a><tt class="docutils literal"><span class="pre">&lt;F()&gt;::type</span></tt>.<a class="footnote-reference" href="#no-result-of" id="id11" name="id11"><sup>2</sup></a></td>
371</tr>
372<tr class="field"><th class="field-name">Returns:</th><td class="field-body">a <a class="reference" href="#tagged-lazy-default">tagged lazy default</a> with <em>value</em> <tt class="docutils literal"><span class="pre">g</span></tt> and <a class="reference" href="#kw">keyword</a> <tt class="docutils literal"><span class="pre">Tag</span></tt>.</td>
373</tr>
374</tbody>
375</table>
376</dd>
377</dl>
378<dl class="docutils" id="get">
379<dt><tt class="docutils literal"><span class="pre">get</span></tt></dt>
380<dd><pre class="first literal-block">
381static keyword&lt;Tag&gt;&amp; get();
382</pre>
383<table class="last docutils field-list" frame="void" rules="none">
384<col class="field-name" />
385<col class="field-body" />
386<tbody valign="top">
387<tr class="field"><th class="field-name">Returns:</th><td class="field-body">a “singleton instance”: the same object will be
388returned on each invocation of <tt class="docutils literal"><span class="pre">get()</span></tt>.</td>
389</tr>
390<tr class="field"><th class="field-name">Thread Safety:</th><td class="field-body"><tt class="docutils literal"><span class="pre">get()</span></tt> can be called from multiple threads
391simultaneously.</td>
392</tr>
393</tbody>
394</table>
395</dd>
396</dl>
397</div>
398<div class="section">
399<h2><a class="toc-backref" href="#id41" id="parameters" name="parameters">4.2&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">parameters</span></tt></a></h2>
400<p>Provides an interface for assembling the actual arguments to a
401<cite>forwarding function</cite> into an <span class="concept">ArgumentPack</span>, in which any
402<a class="reference" href="#positional">positional</a> arguments will be tagged according to the
403corresponding template argument to <tt class="docutils literal"><span class="pre">parameters</span></tt>.</p>
404<table class="docutils field-list" frame="void" rules="none">
405<col class="field-name" />
406<col class="field-body" />
407<tbody valign="top">
408<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/parameters.hpp">boost/parameter/parameters.hpp</a></td>
409</tr>
410</tbody>
411</table>
412<pre class="literal-block">
413template &lt;class P0 = <em>unspecified</em>, class P1 = <em>unspecified</em>, …class Pβ = <em>unspecified</em>&gt;
414struct parameters
415{
416    template &lt;class A0, class A1 = <em>unspecified</em>, …class Aβ = <em>unspecified</em>&gt;
417    struct <a class="reference" href="#match">match</a>
418    {
419        typedef … type;
420    };
421
422    template &lt;class A0&gt;
423    <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> <a class="reference" href="#id13">operator()</a>(A0&amp; a0) const;
424
425    template &lt;class A0, class A1&gt;
426    <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> <a class="reference" href="#id13">operator()</a>(A0&amp; a0, A1&amp; a1) const;
427
428    <span class="vellipsis">⋮</span>
429
430    template &lt;class A0, class A1, …class Aβ&gt;
431    <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> <a class="reference" href="#id13">operator()</a>(A0&amp; a0, A1&amp; a1, …Aβ&amp; aβ) const;
432};
433</pre>
434<table class="docutils field-list" frame="void" rules="none">
435<col class="field-name" />
436<col class="field-body" />
437<tbody valign="top">
438<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><tt class="docutils literal"><span class="pre">P0</span></tt>, <tt class="docutils literal"><span class="pre">P1</span></tt>, … <tt class="docutils literal"><span class="pre">P</span></tt>β are models of <a class="reference" href="#parameterspec"><span class="concept">ParameterSpec</span></a>.</td>
439</tr>
440</tbody>
441</table>
442<div class="note">
443<p class="first admonition-title">Note</p>
444<p>In this section, <tt class="docutils literal"><span class="pre">R</span></tt><em>i</em> and <tt class="docutils literal"><span class="pre">K</span></tt><em>i</em> are defined as
445follows, for any argument type <tt class="docutils literal"><span class="pre">A</span></tt><em>i</em>:</p>
446<blockquote class="last">
447<div class="line-block">
448<div class="line">let <tt class="docutils literal"><span class="pre">D0</span></tt> the set [d0, …, d<em>j</em>] of all <strong>deduced</strong> <em>parameter specs</em> in [<tt class="docutils literal"><span class="pre">P0</span></tt>, …, <tt class="docutils literal"><span class="pre">P</span></tt>β]</div>
449<div class="line"><tt class="docutils literal"><span class="pre">R</span></tt><em>i</em> is <tt class="docutils literal"><span class="pre">A</span></tt><em>i</em>'s <a class="reference" href="#intended-argument-type">intended argument type</a></div>
450<div class="line"><br /></div>
451<div class="line">if <tt class="docutils literal"><span class="pre">A</span></tt><em>i</em> is a result type of <tt class="docutils literal"><span class="pre">keyword&lt;T&gt;::</span></tt><a class="reference" href="#operator"><tt class="docutils literal"><span class="pre">operator=</span></tt></a></div>
452<div class="line">then</div>
453<div class="line-block">
454<div class="line"><tt class="docutils literal"><span class="pre">K</span></tt><em>i</em> is <tt class="docutils literal"><span class="pre">T</span></tt></div>
455</div>
456<div class="line">else</div>
457<div class="line-block">
458<div class="line">if some <tt class="docutils literal"><span class="pre">A</span></tt><em>j</em> where <em>j</em>≤<em>i</em> is a result type of <tt class="docutils literal"><span class="pre">keyword&lt;T&gt;::</span></tt><a class="reference" href="#operator"><tt class="docutils literal"><span class="pre">operator=</span></tt></a></div>
459<div class="line"><em>or</em> some <tt class="docutils literal"><span class="pre">P</span></tt><em>j</em> in <em>j</em>≤<em>i</em> is <strong>deduced</strong></div>
460<div class="line">then</div>
461<div class="line-block">
462<div class="line">if some <em>parameter spec</em> <tt class="docutils literal"><span class="pre">d</span></tt><em>j</em> in <tt class="docutils literal"><span class="pre">D</span></tt><em>i</em> matches <tt class="docutils literal"><span class="pre">A</span></tt><em>i</em></div>
463<div class="line">then</div>
464<div class="line-block">
465<div class="line"><tt class="docutils literal"><span class="pre">K</span></tt><em>i</em> is <tt class="docutils literal"><span class="pre">d</span></tt><em>j</em>'s <a class="reference" href="#keyword-tag-type">keyword tag type</a>.</div>
466<div class="line"><tt class="docutils literal"><span class="pre">D</span></tt><sub>i+1</sub> is <tt class="docutils literal"><span class="pre">D</span></tt><em>i</em> - [<tt class="docutils literal"><span class="pre">d</span></tt><em>j</em>]</div>
467</div>
468</div>
469<div class="line">else</div>
470<div class="line-block">
471<div class="line"><tt class="docutils literal"><span class="pre">K</span></tt><em>i</em> is <tt class="docutils literal"><span class="pre">P</span></tt><em>i</em>'s <a class="reference" href="#keyword-tag-type">keyword tag type</a>.</div>
472</div>
473</div>
474</div>
475</blockquote>
476</div>
477<dl class="docutils" id="match">
478<dt><tt class="docutils literal"><span class="pre">match</span></tt></dt>
479<dd><p class="first">A <a class="reference" href="../../../mpl/doc/refmanual/metafunction.html"><span class="concept">Metafunction</span></a> used to remove a <a class="reference" href="index.html#forwarding-functions">forwarding function</a> from overload resolution.</p>
480<table class="docutils field-list" frame="void" rules="none">
481<col class="field-name" />
482<col class="field-body" />
483<tbody valign="top">
484<tr class="field"><th class="field-name">Returns:</th><td class="field-body">if <tt class="docutils literal"><span class="pre">P0</span></tt>, <tt class="docutils literal"><span class="pre">P1</span></tt>, …<tt class="docutils literal"><span class="pre">P</span></tt>β are <em>satisfied</em> (see
485below), then <tt class="docutils literal"><span class="pre">parameters&lt;P0,P1,…Pβ&gt;</span></tt>.  Otherwise,
486<tt class="docutils literal"><span class="pre">match&lt;A0,A1,…Aβ&gt;::type</span></tt> is not defined.</td>
487</tr>
488</tbody>
489</table>
490<p><tt class="docutils literal"><span class="pre">P0</span></tt>, <tt class="docutils literal"><span class="pre">P1</span></tt>, …<tt class="docutils literal"><span class="pre">P</span></tt>β are <strong>satisfied</strong> if, for
491every <em>j</em> in 0…β, either:</p>
492<ul class="last simple">
493<li><tt class="docutils literal"><span class="pre">P</span></tt><em>j</em> is the <em>unspecified</em> default</li>
494<li><strong>or</strong>, <tt class="docutils literal"><span class="pre">P</span></tt><em>j</em> is a <em>keyword tag type</em></li>
495<li><strong>or</strong>, <tt class="docutils literal"><span class="pre">P</span></tt><em>j</em> is <a class="reference" href="#optional"><tt class="docutils literal"><span class="pre">optional</span></tt></a> <tt class="docutils literal"><span class="pre">&lt;X,F&gt;</span></tt> and either<ul>
496<li><tt class="docutils literal"><span class="pre">X</span></tt> is not <tt class="docutils literal"><span class="pre">K</span></tt><em>i</em> for any <em>i</em>,</li>
497<li><strong>or</strong> <tt class="docutils literal"><span class="pre">X</span></tt> is some <tt class="docutils literal"><span class="pre">K</span></tt><em>i</em>  and <tt class="docutils literal"><span class="pre">mpl::apply&lt;F,R</span></tt><em>i</em><tt class="docutils literal"><span class="pre">&gt;::type::value</span></tt> is <tt class="docutils literal"><span class="pre">true</span></tt></li>
498</ul>
499</li>
500<li><strong>or</strong>, <tt class="docutils literal"><span class="pre">P</span></tt><em>j</em> is <a class="reference" href="#required"><tt class="docutils literal"><span class="pre">required</span></tt></a> <tt class="docutils literal"><span class="pre">&lt;X,F&gt;</span></tt>, and<ul>
501<li><tt class="docutils literal"><span class="pre">X</span></tt> is some <tt class="docutils literal"><span class="pre">K</span></tt><em>i</em>, <strong>and</strong></li>
502<li><tt class="docutils literal"><span class="pre">mpl::apply&lt;F,R</span></tt><em>i</em><tt class="docutils literal"><span class="pre">&gt;::type::value</span></tt> is <tt class="docutils literal"><span class="pre">true</span></tt></li>
503</ul>
504</li>
505</ul>
506</dd>
507</dl>
508<dl class="docutils" id="id13">
509<dt><tt class="docutils literal"><span class="pre">operator()</span></tt></dt>
510<dd><pre class="first literal-block">
511template &lt;class A0&gt; <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> operator()(A0 const&amp; a0) const;
512
513<span class="vellipsis">⋮</span>
514
515template &lt;class A0, …class Aβ&gt; <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> <a class="reference" href="#id13">operator()</a>(A0 const&amp; a0, …Aβ const&amp; aβ) const;
516</pre>
517<table class="last docutils field-list" frame="void" rules="none">
518<col class="field-name" />
519<col class="field-body" />
520<tbody valign="top">
521<tr class="field"><th class="field-name">Returns:</th><td class="field-body"><p class="first">An <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a> containing, for each <tt class="docutils literal"><span class="pre">a</span></tt><em>i</em>,</p>
522<ul class="last simple">
523<li>if <tt class="docutils literal"><span class="pre">a</span></tt><em>i</em>,  is a single-element <span class="concept">ArgumentPack</span>, its element</li>
524<li>Otherwise, a <a class="reference" href="#tagged-reference">tagged reference</a> with <a class="reference" href="#kw">keyword</a> <tt class="docutils literal"><span class="pre">K</span></tt><em>i</em> and <em>value</em> <tt class="docutils literal"><span class="pre">a</span></tt><em>i</em></li>
525</ul>
526</td>
527</tr>
528</tbody>
529</table>
530</dd>
531</dl>
532</div>
533<div class="section">
534<h2><a class="toc-backref" href="#id42" id="optional-required" name="optional-required"><span id="required"></span><span id="optional"></span>4.3&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">optional</span></tt>, <tt class="docutils literal"><span class="pre">required</span></tt></a></h2>
535<p>These templates describe the requirements on a function parameter.</p>
536<table class="docutils field-list" frame="void" rules="none">
537<col class="field-name" />
538<col class="field-body" />
539<tbody valign="top">
540<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/parameters.hpp">boost/parameter/parameters.hpp</a></td>
541</tr>
542</tbody>
543</table>
544<table class="docutils field-list" frame="void" rules="none">
545<col class="field-name" />
546<col class="field-body" />
547<tbody valign="top">
548<tr class="field"><th class="field-name" colspan="2">Specializations model:</th></tr>
549<tr><td>&nbsp;</td><td class="field-body"><a class="reference" href="#parameterspec"><span class="concept">ParameterSpec</span></a></td>
550</tr>
551</tbody>
552</table>
553<pre class="literal-block">
554template &lt;class Tag, class Predicate = <em>unspecified</em>&gt;
555struct optional;
556
557template &lt;class Tag, class Predicate = <em>unspecified</em>&gt;
558struct required;
559</pre>
560<p>The default value of <tt class="docutils literal"><span class="pre">Predicate</span></tt> is an unspecified <a class="reference" href="../../../mpl/doc/refmanual/metafunction.html"><span class="concept">Metafunction</span></a> that returns
561<tt class="docutils literal"><span class="pre">mpl::true_</span></tt> for any argument.</p>
562</div>
563<div class="section">
564<h2><a class="toc-backref" href="#id43" id="deduced" name="deduced">4.4&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">deduced</span></tt></a></h2>
565<p>This template is used to wrap the <em>keyword tag</em> argument to
566<tt class="docutils literal"><span class="pre">optional</span></tt> or <tt class="docutils literal"><span class="pre">required</span></tt>.</p>
567<table class="docutils field-list" frame="void" rules="none">
568<col class="field-name" />
569<col class="field-body" />
570<tbody valign="top">
571<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/parameters.hpp">boost/parameter/parameters.hpp</a></td>
572</tr>
573</tbody>
574</table>
575<pre class="literal-block">
576template &lt;class Tag&gt;
577struct deduced;
578</pre>
579</div>
580</div>
581<hr class="docutils" />
582<div class="section">
583<h1><a class="toc-backref" href="#id44" id="metafunctions" name="metafunctions">5&nbsp;&nbsp;&nbsp;Metafunctions</a></h1>
584<p>A <a class="reference" href="../../../mpl/doc/refmanual/metafunction.html"><span class="concept">Metafunction</span></a> is conceptually a function that operates on, and
585returns, C++ types.</p>
586<div class="section">
587<h2><a class="toc-backref" href="#id45" id="binding" name="binding">5.1&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">binding</span></tt></a></h2>
588<p>Returns the result type of indexing an argument pack with a
589<a class="reference" href="#keyword-tag-type">keyword tag type</a> or with a <a class="reference" href="#tagged-default">tagged default</a>.</p>
590<table class="docutils field-list" frame="void" rules="none">
591<col class="field-name" />
592<col class="field-body" />
593<tbody valign="top">
594<tr class="field"><th class="field-name">Defined n:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/binding.hpp">boost/parameter/binding.hpp</a></td>
595</tr>
596</tbody>
597</table>
598<pre class="literal-block">
599template &lt;class A, class K, class D = void&gt;
600struct binding
601{
602    typedef … type;
603};
604</pre>
605<table class="docutils field-list" frame="void" rules="none">
606<col class="field-name" />
607<col class="field-body" />
608<tbody valign="top">
609<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><tt class="docutils literal"><span class="pre">A</span></tt> is a model of <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a>.</td>
610</tr>
611<tr class="field"><th class="field-name">Returns:</th><td class="field-body">the reference type of the <a class="reference" href="#tagged-reference">tagged reference</a> in <tt class="docutils literal"><span class="pre">A</span></tt>
612having <a class="reference" href="#keyword-tag-type">keyword tag type</a> <tt class="docutils literal"><span class="pre">K</span></tt>, if any.  If no such <a class="reference" href="#tagged-reference">tagged reference</a> exists, returns <tt class="docutils literal"><span class="pre">D</span></tt>.</td>
613</tr>
614</tbody>
615</table>
616</div>
617<div class="section">
618<h2><a class="toc-backref" href="#id46" id="lazy-binding" name="lazy-binding">5.2&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">lazy_binding</span></tt></a></h2>
619<p>Returns the result type of indexing an argument pack with a <a class="reference" href="#tagged-lazy-default">tagged lazy default</a>.</p>
620<table class="docutils field-list" frame="void" rules="none">
621<col class="field-name" />
622<col class="field-body" />
623<tbody valign="top">
624<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/binding.hpp">boost/parameter/binding.hpp</a></td>
625</tr>
626</tbody>
627</table>
628<pre class="literal-block">
629template &lt;class A, class K, class F&gt;
630struct lazy_binding
631{
632    typedef … type;
633};
634</pre>
635<table class="docutils field-list" frame="void" rules="none">
636<col class="field-name" />
637<col class="field-body" />
638<tbody valign="top">
639<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><tt class="docutils literal"><span class="pre">A</span></tt> is a model of <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a>.</td>
640</tr>
641<tr class="field"><th class="field-name">Returns:</th><td class="field-body">the reference type of the <a class="reference" href="#tagged-reference">tagged reference</a> in <tt class="docutils literal"><span class="pre">A</span></tt>
642having <a class="reference" href="#keyword-tag-type">keyword tag type</a> <tt class="docutils literal"><span class="pre">K</span></tt>, if any.  If no such <a class="reference" href="#tagged-reference">tagged reference</a> exists, returns <tt class="docutils literal"><span class="pre">boost::</span></tt><a class="reference" href="../../../utility/utility.htm#result_of"><tt class="docutils literal"><span class="pre">result_of</span></tt></a><tt class="docutils literal"><span class="pre">&lt;F()&gt;::type</span></tt>.<a class="footnote-reference" href="#no-result-of" id="id18" name="id18"><sup>2</sup></a></td>
643</tr>
644</tbody>
645</table>
646</div>
647<div class="section">
648<h2><a class="toc-backref" href="#id47" id="value-type" name="value-type">5.3&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">value_type</span></tt></a></h2>
649<p>Returns the result type of indexing an argument pack with a
650<a class="reference" href="#keyword-tag-type">keyword tag type</a> or with a <a class="reference" href="#tagged-default">tagged default</a>.</p>
651<table class="docutils field-list" frame="void" rules="none">
652<col class="field-name" />
653<col class="field-body" />
654<tbody valign="top">
655<tr class="field"><th class="field-name">Defined n:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/value_type.hpp">boost/parameter/value_type.hpp</a></td>
656</tr>
657</tbody>
658</table>
659<pre class="literal-block">
660template &lt;class A, class K, class D = void&gt;
661struct value_type
662{
663    typedef … type;
664};
665</pre>
666<table class="docutils field-list" frame="void" rules="none">
667<col class="field-name" />
668<col class="field-body" />
669<tbody valign="top">
670<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><p class="first"><tt class="docutils literal"><span class="pre">A</span></tt> is a model of <a class="reference" href="#argumentpack"><span class="concept">ArgumentPack</span></a>.</p>
671</td>
672</tr>
673<tr class="field"><th class="field-name">Returns:</th><td class="field-body"><p class="first">the type of the <a class="reference" href="#tagged-reference">tagged reference</a> in <tt class="docutils literal"><span class="pre">A</span></tt>
674having <a class="reference" href="#keyword-tag-type">keyword tag type</a> <tt class="docutils literal"><span class="pre">K</span></tt>, if any.  If no such <a class="reference" href="#tagged-reference">tagged reference</a> exists, returns <tt class="docutils literal"><span class="pre">D</span></tt>. Equivalent to:</p>
675<pre class="literal-block">
676typename remove_reference&lt;
677  typename binding&lt;A, K, D&gt;::type
678&gt;::type
679</pre>
680<p class="last">… when <tt class="docutils literal"><span class="pre">D</span></tt> is not a reference type.</p>
681</td>
682</tr>
683</tbody>
684</table>
685</div>
686</div>
687<hr class="docutils" />
688<div class="section">
689<h1><a class="toc-backref" href="#id48" id="code-generation-macros" name="code-generation-macros">6&nbsp;&nbsp;&nbsp;Code Generation Macros</a></h1>
690<p>Macros in this section can be used to ease the writing of code
691using the Parameter libray by eliminating repetitive boilerplate.</p>
692<div class="section">
693<h2><a class="toc-backref" href="#id49" id="boost-parameter-function-result-name-tag-namespace-arguments" name="boost-parameter-function-result-name-tag-namespace-arguments">6.1&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_FUNCTION(result,name,tag_namespace,arguments)</span></tt></a></h2>
694<table class="docutils field-list" frame="void" rules="none">
695<col class="field-name" />
696<col class="field-body" />
697<tbody valign="top">
698<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/preprocessor.hpp">boost/parameter/preprocessor.hpp</a></td>
699</tr>
700</tbody>
701</table>
702<table class="docutils field-list" frame="void" rules="none">
703<col class="field-name" />
704<col class="field-body" />
705<tbody valign="top">
706<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><p class="first"><tt class="docutils literal"><span class="pre">result</span></tt> is the parenthesized return type of the function.
707<tt class="docutils literal"><span class="pre">name</span></tt> is the base name of the function, this is the name of the
708generated forwarding functions. <tt class="docutils literal"><span class="pre">tag_namespace</span></tt> is the namespace in
709which the keywords used by the function resides. <tt class="docutils literal"><span class="pre">arguments</span></tt> is
710a list of <em>argument specifiers</em>, as defined below.</p>
711</td>
712</tr>
713<tr class="field"><th class="field-name" colspan="2">Argument specifiers syntax:</th></tr>
714<tr><td>&nbsp;</td><td class="field-body"><pre class="first literal-block">
715argument-specifiers ::= <em>specifier-group</em> {<em>specifier-group</em>}
716
717specifier-group0 ::= <em>specifier-group1</em> |
718                     ( '<strong>(</strong>' '<strong>deduced</strong>' <em>specifier-group1</em> {<em>specifier-group1</em>} '<strong>)</strong>' )
719
720specifier-group1 ::= ( '<strong>(</strong>' '<strong>optional</strong>' <em>optional-specifier</em> {<em>optional-specifier</em>} '<strong>)</strong>' ) |
721                     ( '<strong>(</strong>' '<strong>required</strong>' <em>required-specifier</em> {<em>required-specifier</em>} '<strong>)</strong>' )
722
723optional-specifier ::= '<strong>(</strong>' <em>name</em> '<strong>,</strong>' <em>restriction</em> '<strong>,</strong>' <em>default-value</em> ')'
724required-specifier ::= '<strong>(</strong>' <em>name</em> '<strong>,</strong>' <em>restriction</em> ')'
725
726restriction ::= ('<strong>*</strong>' '<strong>(</strong>' <em>lambda-expression</em> '<strong>)</strong>' ) |
727                ( '<strong>(</strong>' <em>typename</em> '<strong>)</strong>' ) |
728                '<strong>*</strong>'
729</pre>
730<p class="last"><tt class="docutils literal"><span class="pre">name</span></tt> is any valid C++ identifier. <tt class="docutils literal"><span class="pre">default-value</span></tt> is any valid
731C++ expression. <tt class="docutils literal"><span class="pre">typename</span></tt> is the name of a type.
732<tt class="docutils literal"><span class="pre">lambda-expression</span></tt> is an <a class="reference" href="../../../mpl/doc/refmanual/lambda-expression.html">MPL lambda expression</a>.</p>
733</td>
734</tr>
735</tbody>
736</table>
737<table class="docutils field-list" frame="void" rules="none">
738<col class="field-name" />
739<col class="field-body" />
740<tbody valign="top">
741<tr class="field"><th class="field-name" colspan="2">Generated names in enclosing scope:</th></tr>
742<tr><td>&nbsp;</td><td class="field-body"><ul class="first last simple">
743<li><tt class="docutils literal"><span class="pre">boost_param_result_</span> <span class="pre">##</span> <span class="pre">__LINE__</span> <span class="pre">##</span> <span class="pre">name</span></tt></li>
744<li><tt class="docutils literal"><span class="pre">boost_param_params_</span> <span class="pre">##</span> <span class="pre">__LINE__</span> <span class="pre">##</span> <span class="pre">name</span></tt></li>
745<li><tt class="docutils literal"><span class="pre">boost_param_parameters_</span> <span class="pre">##</span> <span class="pre">__LINE__</span> <span class="pre">##</span> <span class="pre">name</span></tt></li>
746<li><tt class="docutils literal"><span class="pre">boost_param_impl</span> <span class="pre">##</span> <span class="pre">name</span></tt></li>
747<li><tt class="docutils literal"><span class="pre">boost_param_default_</span> <span class="pre">##</span> <span class="pre">__LINE__</span> <span class="pre">##</span> <span class="pre">name</span></tt></li>
748</ul>
749</td>
750</tr>
751</tbody>
752</table>
753<dl class="docutils">
754<dt>Approximate expansion:</dt>
755<dd><p class="first"><strong>Where</strong>:</p>
756<ul class="simple">
757<li><tt class="docutils literal"><span class="pre">n</span></tt> denotes the <em>minimum</em> arity, as determined from <tt class="docutils literal"><span class="pre">arguments</span></tt>.</li>
758<li><tt class="docutils literal"><span class="pre">m</span></tt> denotes the <em>maximum</em> arity, as determined from <tt class="docutils literal"><span class="pre">arguments</span></tt>.</li>
759</ul>
760<pre class="last literal-block">
761template &lt;class T&gt;
762struct boost_param_result_ ## __LINE__ ## <strong>name</strong>
763{
764    typedef <strong>result</strong> type;
765};
766
767struct boost_param_params_ ## __LINE__ ## <strong>name</strong>
768  : boost::parameter::parameters&lt;
769        <em>list of parameter specifications, based on arguments</em>
770    &gt;
771{};
772
773typedef boost_param_params_ ## __LINE__ ## <strong>name</strong>
774  boost_param_parameters_ ## __LINE__ ## <strong>name</strong>;
775
776template &lt;class A0, …, class A<strong>n</strong>&gt;
777<em>result type</em> <strong>name</strong>(
778    A0 <em>cv</em>&amp; a0, …, A<strong>n</strong> <em>cv</em>&amp; a<strong>n</strong>
779  , typename boost_param_parameters_ ## __LINE__ ## <strong>name</strong>::match&lt;
780      A0 <em>cv</em>, …, A<strong>n</strong> <em>cv</em>
781    &gt;::type = boost_param_parameters_ ## __LINE__ ## <strong>name</strong>()
782)
783{
784    <em>… forward to implementation …</em>
785}
786
787<span class="vellipsis">⋮</span>
788
789template &lt;class A0, …, class A<strong>m</strong>&gt;
790<em>result type</em> <strong>name</strong>(
791    A0 <em>cv</em>&amp; a0, …, A<strong>m</strong> <em>cv</em>&amp; a<strong>m</strong>
792  , typename boost_param_parameters_ ## __LINE__ ## <strong>name</strong>::match&lt;
793      A0 <em>cv</em>, …, A<strong>m</strong> <em>cv</em>
794    &gt;::type = boost_param_parameters_ ## __LINE__ ## <strong>name</strong>()
795)
796{
797    <em>… forward to implementation …</em>
798}
799
800template &lt;
801    class ResultType
802  , class <em>argument name</em><strong>0</strong> ## _type
803    …
804  , class <em>argument name</em><strong>m</strong> ## _type
805&gt;
806ResultType boost_param_default_ ## __LINE__ ## <strong>name</strong>(
807    (ResultType(*)())
808  , <em>argument name</em><strong>0</strong> ## _type&amp; <em>argument name</em><strong>0</strong>
809    …
810  , <em>argument name</em><strong>m</strong> ## _type&amp; <em>argument name</em><strong>m</strong>
811)
812</pre>
813</dd>
814</dl>
815</div>
816<div class="section">
817<h2><a class="toc-backref" href="#id50" id="boost-parameter-member-function-result-name-tag-namespace-arguments" name="boost-parameter-member-function-result-name-tag-namespace-arguments">6.2&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_MEMBER_FUNCTION(result,name,tag_namespace,arguments)</span></tt></a></h2>
818<table class="docutils field-list" frame="void" rules="none">
819<col class="field-name" />
820<col class="field-body" />
821<tbody valign="top">
822<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/preprocessor.hpp">boost/parameter/preprocessor.hpp</a></td>
823</tr>
824</tbody>
825</table>
826<p>See <tt class="docutils literal"><span class="pre">BOOST_PARAMETER_FUNCTION(result,name,tag_namespace,arguments)</span></tt></p>
827</div>
828<div class="section">
829<h2><a class="toc-backref" href="#id51" id="boost-parameter-constructor-cls-impl-tag-namespace-arguments" name="boost-parameter-constructor-cls-impl-tag-namespace-arguments">6.3&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_CONSTRUCTOR(cls,</span> <span class="pre">impl,</span> <span class="pre">tag_namespace,</span> <span class="pre">arguments)</span></tt></a></h2>
830<table class="docutils field-list" frame="void" rules="none">
831<col class="field-name" />
832<col class="field-body" />
833<tbody valign="top">
834<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/preprocessor.hpp">boost/parameter/preprocessor.hpp</a></td>
835</tr>
836</tbody>
837</table>
838<table class="docutils field-list" frame="void" rules="none">
839<col class="field-name" />
840<col class="field-body" />
841<tbody valign="top">
842<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><p class="first"><tt class="docutils literal"><span class="pre">cls</span></tt> is the name of this class. <tt class="docutils literal"><span class="pre">impl</span></tt> is the
843parenthesized implementation base class for <tt class="docutils literal"><span class="pre">cls</span></tt>.
844<tt class="docutils literal"><span class="pre">tag_namespace</span></tt> is the namespace in which the keywords
845used by the function resides. <tt class="docutils literal"><span class="pre">arguments</span></tt> is
846a list of <em>argument specifiers</em>, as defined in
847<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_FUNCTION(result,name,tag_namespace,arguments)</span></tt>.</p>
848</td>
849</tr>
850<tr class="field"><th class="field-name" colspan="2">Generated names in enclosing scope:</th></tr>
851<tr><td>&nbsp;</td><td class="field-body"><ul class="first last simple">
852<li><tt class="docutils literal"><span class="pre">boost_param_params_</span> <span class="pre">##</span> <span class="pre">__LINE__</span> <span class="pre">##</span> <span class="pre">ctor</span></tt></li>
853<li><tt class="docutils literal"><span class="pre">constructor_parameters</span> <span class="pre">##</span> <span class="pre">__LINE__</span></tt></li>
854</ul>
855</td>
856</tr>
857</tbody>
858</table>
859<dl class="docutils">
860<dt>Approximate expansion:</dt>
861<dd><p class="first"><strong>Where</strong>:</p>
862<ul class="simple">
863<li><tt class="docutils literal"><span class="pre">n</span></tt> denotes the <em>minimum</em> arity, as determined from <tt class="docutils literal"><span class="pre">arguments</span></tt>.</li>
864<li><tt class="docutils literal"><span class="pre">m</span></tt> denotes the <em>maximum</em> arity, as determined from <tt class="docutils literal"><span class="pre">arguments</span></tt>.</li>
865</ul>
866<pre class="last literal-block">
867struct boost_param_params_ ## __LINE__ ## ctor
868  : boost::parameter::parameters&lt;
869        <em>list of parameter specifications, based on arguments</em>
870    &gt;
871{};
872
873typedef boost_param_params_ ## __LINE__ ## <strong>name</strong>
874  constructor_parameters ## __LINE__;
875
876template &lt;class A0, …, class A<strong>n</strong>&gt;
877<em>cls</em>(A0 const&amp; a0, …, A<strong>n</strong> const&amp; a<strong>n</strong>)
878  : <em>impl</em>(constructor_parameters ## __LINE__(a0, …, a<strong>n</strong>))
879{}
880
881<span class="vellipsis">⋮</span>
882
883template &lt;class A0, …, class A<strong>m</strong>&gt;
884<em>cls</em>(A0 const&amp; a0, …, A<strong>n</strong> const&amp; a<strong>m</strong>)
885  : <em>impl</em>(constructor_parameters ## __LINE__(a0, …, a<strong>m</strong>))
886{}
887</pre>
888</dd>
889</dl>
890</div>
891<div class="section">
892<h2><a class="toc-backref" href="#id52" id="boost-parameter-name-name" name="boost-parameter-name-name">6.4&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_NAME(name)</span></tt></a></h2>
893<p>Declares a tag-type and keyword object.</p>
894<p>Expands to:</p>
895<p><strong>If</strong> <em>name</em> is of the form:</p>
896<pre class="literal-block">
897(<em>tag-name</em>, <em>namespace-name</em>) <em>object-name</em>
898</pre>
899<p><strong>then</strong></p>
900<pre class="literal-block">
901namespace <em>namespace-name</em>
902{
903  struct <em>tag-name</em>
904  {
905      static char const* keyword_name()
906      {
907          return ##<em>tag-name</em>;
908      }
909
910      typedef <em>implementation defined</em> _;
911      typedef <em>implementation defined</em> _1;
912  };
913}
914
915::boost::parameter::keyword&lt;<em>tag-namespace</em>::<em>tag-name</em>&gt; const&amp; <em>object-name</em>
916    = ::boost::parameter::keyword&lt;<em>tag-namespace</em>::<em>tag-name</em>&gt;::instance;
917</pre>
918<p><strong>Else</strong></p>
919<pre class="literal-block">
920namespace tag
921{
922  struct <em>name</em>
923  {
924      static char const* keyword_name()
925      {
926          return ##<em>name</em>;
927      }
928
929      typedef <em>implementation defined</em> _;
930      typedef <em>implementation defined</em> _1;
931  };
932}
933
934::boost::parameter::keyword&lt;tag::<em>name</em>&gt; const&amp; _<em>name</em>
935    = ::boost::parameter::keyword&lt;tag::<em>name</em>&gt;::instance;
936</pre>
937</div>
938<div class="section">
939<h2><a class="toc-backref" href="#id53" id="boost-parameter-template-keyword-name" name="boost-parameter-template-keyword-name">6.5&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_TEMPLATE_KEYWORD(name)</span></tt></a></h2>
940<p>Expands to:</p>
941<pre class="literal-block">
942namespace tag
943{
944  struct <em>name</em>;
945}
946
947template &lt;class T&gt;
948struct <em>name</em>
949  : ::boost::parameter::template_keyword&lt;tag::<em>name</em>, T&gt;
950{};
951</pre>
952</div>
953<div class="section">
954<h2><a class="toc-backref" href="#id54" id="boost-parameter-fun-r-n-l-h-p" name="boost-parameter-fun-r-n-l-h-p">6.6&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_FUN(r,n,l,h,p)</span></tt></a></h2>
955<div class="admonition-deprecated admonition">
956<p class="first admonition-title">Deprecated</p>
957<p class="last">This macro has been deprecated in favor of
958<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_FUNCTION</span></tt>.</p>
959</div>
960<p>Generates a sequence of <a class="reference" href="index.html#forwarding-functions">forwarding function</a> templates named
961<tt class="docutils literal"><span class="pre">n</span></tt>, with arities ranging from <tt class="docutils literal"><span class="pre">l</span></tt> to <tt class="docutils literal"><span class="pre">h</span></tt> , returning <tt class="docutils literal"><span class="pre">r</span></tt>,
962and using <tt class="docutils literal"><span class="pre">p</span></tt> to control overload resolution and assign tags to
963positional arguments.</p>
964<table class="docutils field-list" frame="void" rules="none">
965<col class="field-name" />
966<col class="field-body" />
967<tbody valign="top">
968<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/macros.hpp">boost/parameter/macros.hpp</a></td>
969</tr>
970</tbody>
971</table>
972<table class="docutils field-list" frame="void" rules="none">
973<col class="field-name" />
974<col class="field-body" />
975<tbody valign="top">
976<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><tt class="docutils literal"><span class="pre">l</span></tt> and <tt class="docutils literal"><span class="pre">h</span></tt> are nonnegative integer tokens such
977that <tt class="docutils literal"><span class="pre">l</span></tt> &lt; <tt class="docutils literal"><span class="pre">h</span></tt></td>
978</tr>
979</tbody>
980</table>
981<dl class="docutils">
982<dt>Generates</dt>
983<dd><pre class="first last literal-block">
984template &lt;class A1, class A2, …class A##<strong>l</strong>&gt;
985r name(
986    A1 const&amp; a1, A2 const&amp; a2, …A<strong>l</strong> const&amp; x<strong>l</strong>
987  , typename <strong>p</strong>::match&lt;A1,A2,…A<strong>l</strong>&gt;::type p = <strong>p</strong>())
988{
989   return <strong>name</strong>_with_named_params(<strong>p</strong>(x1,x2,…x<strong>l</strong>));
990}
991
992template &lt;class A1, class A2, …class A<strong>l</strong>, class A##<a class="reference" href="../../../preprocessor/doc/ref/inc.html">BOOST_PP_INC</a>(<strong>l</strong>)&gt;
993r name(
994    A1 const&amp; a1, A2 const&amp; a2, …A<strong>l</strong> const&amp; x<strong>l</strong>
995  , A##<a class="reference" href="../../../preprocessor/doc/ref/inc.html">BOOST_PP_INC</a>(<strong>l</strong>) const&amp; x##<a class="reference" href="../../../preprocessor/doc/ref/inc.html">BOOST_PP_INC</a>(<strong>l</strong>)
996  , typename <strong>p</strong>::match&lt;A1,A2,…A<strong>l</strong>,A##<a class="reference" href="../../../preprocessor/doc/ref/inc.html">BOOST_PP_INC</a>(<strong>l</strong>)&gt;::type p = <strong>p</strong>())
997{
998   return <strong>name</strong>_with_named_params(<strong>p</strong>(x1,x2,…x<strong>l</strong>,x##<a class="reference" href="../../../preprocessor/doc/ref/inc.html">BOOST_PP_INC</a>(<strong>l</strong>)));
999}
1000
1001<span class="vellipsis">⋮</span>
1002
1003template &lt;class A1, class A2, …class A<strong>h</strong>&gt;
1004r name(
1005    A1 const&amp; a1, A2 const&amp; a2, …A<strong>h</strong> const&amp; x<strong>h</strong>
1006  , typename <strong>p</strong>::match&lt;A1,A2,…A<strong>h</strong>&gt;::type p = <strong>p</strong>())
1007{
1008   return <strong>name</strong>_with_named_params(<strong>p</strong>(a1,a2,…a<strong>h</strong>));
1009}
1010</pre>
1011</dd>
1012</dl>
1013</div>
1014<div class="section">
1015<h2><a class="toc-backref" href="#id55" id="boost-parameter-keyword-n-k" name="boost-parameter-keyword-n-k">6.7&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_KEYWORD(n,k)</span></tt></a></h2>
1016<div class="admonition-deprecated admonition">
1017<p class="first admonition-title">Deprecated</p>
1018<p class="last">This macro has been deprecated in favor of
1019<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_NAME</span></tt>.</p>
1020</div>
1021<p>Generates the declaration of a <a class="reference" href="#keyword-tag-type">keyword tag type</a> named <tt class="docutils literal"><span class="pre">k</span></tt> in
1022namespace <tt class="docutils literal"><span class="pre">n</span></tt>, and a corresponding <a class="reference" href="#keyword-object">keyword object</a> definition in
1023the enclosing namespace.</p>
1024<table class="docutils field-list" frame="void" rules="none">
1025<col class="field-name" />
1026<col class="field-body" />
1027<tbody valign="top">
1028<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/keyword.hpp">boost/parameter/keyword.hpp</a></td>
1029</tr>
1030</tbody>
1031</table>
1032<dl class="docutils">
1033<dt>Generates</dt>
1034<dd><pre class="first last literal-block">
1035namespace <strong>n</strong> { struct <strong>k</strong>; }
1036namespace {
1037  boost::parameter::keyword&lt;<em>tag-namespace</em>::<strong>k</strong>&gt;&amp; <strong>k</strong>
1038  = boost::parameter::keyword&lt;<em>tag-namespace</em>::<strong>k</strong>&gt;::get();
1039}
1040</pre>
1041</dd>
1042</dl>
1043</div>
1044<div class="section">
1045<h2><a class="toc-backref" href="#id56" id="boost-parameter-match-p-a-x" name="boost-parameter-match-p-a-x">6.8&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_MATCH(p,a,x)</span></tt></a></h2>
1046<p>Generates a defaulted parameter declaration for a <a class="reference" href="index.html#forwarding-functions">forwarding
1047function</a>.</p>
1048<table class="docutils field-list" frame="void" rules="none">
1049<col class="field-name" />
1050<col class="field-body" />
1051<tbody valign="top">
1052<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/match.hpp">boost/parameter/match.hpp</a></td>
1053</tr>
1054</tbody>
1055</table>
1056<table class="docutils field-list" frame="void" rules="none">
1057<col class="field-name" />
1058<col class="field-body" />
1059<tbody valign="top">
1060<tr class="field"><th class="field-name">Requires:</th><td class="field-body"><p class="first"><tt class="docutils literal"><span class="pre">a</span></tt> is a <a class="reference" href="http://www.boost.org/libs/preprocessor/doc/data.html">Boost.Preprocessor sequence</a>
1061of the form</p>
1062<pre class="last literal-block">
1063(A0)(A1)…(A<em>n</em>)
1064</pre>
1065</td>
1066</tr>
1067</tbody>
1068</table>
1069<dl class="docutils">
1070<dt>Generates</dt>
1071<dd><pre class="first last literal-block">
1072typename <strong>p</strong>::match&lt;<strong>A0</strong>,<strong>A1</strong>…,<strong>A</strong><em>n</em>&gt;::type <strong>x</strong> = <strong>p</strong>()
1073</pre>
1074</dd>
1075</dl>
1076</div>
1077</div>
1078<div class="section">
1079<h1><a class="toc-backref" href="#id57" id="configuration-macros" name="configuration-macros">7&nbsp;&nbsp;&nbsp;Configuration Macros</a></h1>
1080<div class="section">
1081<h2><a class="toc-backref" href="#id58" id="boost-parameter-max-arity" name="boost-parameter-max-arity">7.1&nbsp;&nbsp;&nbsp;<tt class="docutils literal"><span class="pre">BOOST_PARAMETER_MAX_ARITY</span></tt></a></h2>
1082<p>Determines the maximum number of arguments supported by the
1083library.  Will only be <tt class="docutils literal"><span class="pre">#defined</span></tt> by the library if it is not
1084already <tt class="docutils literal"><span class="pre">#defined</span></tt>.</p>
1085<table class="docutils field-list" frame="void" rules="none">
1086<col class="field-name" />
1087<col class="field-body" />
1088<tbody valign="top">
1089<tr class="field"><th class="field-name">Defined in:</th><td class="field-body"><a class="reference" href="../../../../boost/parameter/config.hpp">boost/parameter/config.hpp</a></td>
1090</tr>
1091</tbody>
1092</table>
1093<table class="docutils field-list" frame="void" rules="none">
1094<col class="field-name" />
1095<col class="field-body" />
1096<tbody valign="top">
1097<tr class="field"><th class="field-name">Default Value:</th><td class="field-body"><tt class="docutils literal"><span class="pre">5</span></tt></td>
1098</tr>
1099</tbody>
1100</table>
1101</div>
1102</div>
1103<div class="section">
1104<h1><a class="toc-backref" href="#id59" id="tutorial" name="tutorial">8&nbsp;&nbsp;&nbsp;Tutorial</a></h1>
1105<p>Follow <a class="reference" href="index.html#tutorial">this link</a> to the Boost.Parameter tutorial
1106documentation.</p>
1107<hr class="docutils" />
1108<table class="docutils footnote" frame="void" id="thread" rules="none">
1109<colgroup><col class="label" /><col /></colgroup>
1110<tbody valign="top">
1111<tr><td class="label"><a class="fn-backref" href="#id2" name="thread">[1]</a></td><td>References to tag objects may be initialized multiple
1112times.  This scenario can only occur in the presence of
1113threading.  Because the C++ standard doesn't consider threading,
1114it doesn't explicitly allow or forbid multiple initialization of
1115references.  That said, it's hard to imagine an implementation
1116where it could make a difference.</td></tr>
1117</tbody>
1118</table>
1119<table class="docutils footnote" frame="void" id="no-result-of" rules="none">
1120<colgroup><col class="label" /><col /></colgroup>
1121<tbody valign="top">
1122<tr><td class="label"><a name="no-result-of">[2]</a></td><td><em>(<a class="fn-backref" href="#id11">1</a>, <a class="fn-backref" href="#id18">2</a>)</em> Where <a class="reference" href="../../../utility/utility.htm#BOOST_NO_RESULT_OF"><tt class="docutils literal"><span class="pre">BOOST_NO_RESULT_OF</span></tt></a> is <tt class="docutils literal"><span class="pre">#defined</span></tt>,
1123<tt class="docutils literal"><span class="pre">boost::</span></tt><a class="reference" href="../../../utility/utility.htm#result_of"><tt class="docutils literal"><span class="pre">result_of</span></tt></a><tt class="docutils literal"><span class="pre">&lt;F()&gt;::type</span></tt> is replaced by
1124<tt class="docutils literal"><span class="pre">F::result_type</span></tt>.</td></tr>
1125</tbody>
1126</table>
1127</div>
1128</div>
1129<div class="footer">
1130<hr class="footer" />
1131Generated on: 2007-05-03 14:17 UTC.
1132Generated by <a class="reference" href="http://docutils.sourceforge.net/">Docutils</a> from <a class="reference" href="http://docutils.sourceforge.net/rst.html">reStructuredText</a> source.
1133
1134</div>
1135</body>
1136</html>
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