1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Store an Attribute after a Parser Produced a Pair of Iterators (Qi)</title> 5<link rel="stylesheet" href="../../../../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../../../index.html" title="Spirit 2.5.8"> 8<link rel="up" href="../assign_to.html" title="Store a Parsed Attribute Value (Qi)"> 9<link rel="prev" href="../assign_to.html" title="Store a Parsed Attribute Value (Qi)"> 10<link rel="next" href="assign_to_attribute_from_value.html" title="Store an Attribute Value after a Parser Produced a Value (Qi)"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="../assign_to.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../assign_to.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="assign_to_attribute_from_value.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h5 class="title"> 27<a name="spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators"></a><a class="link" href="assign_to_attribute_from_iterators.html" title="Store an Attribute after a Parser Produced a Pair of Iterators (Qi)">Store 28 an Attribute after a Parser Produced a Pair of Iterators (Qi)</a> 29</h5></div></div></div> 30<h6> 31<a name="spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.h0"></a> 32 <span class="phrase"><a name="spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.assign_to_attribute_from_iterators"></a></span><a class="link" href="assign_to_attribute_from_iterators.html#spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.assign_to_attribute_from_iterators">assign_to_attribute_from_iterators</a> 33 </h6> 34<p> 35 The template <code class="computeroutput"><span class="identifier">assign_to_attribute_from_iterators</span></code> 36 is a type used as an attribute customization point. It is invoked by 37 the those <span class="emphasis"><em>Qi</em></span> parsers not producing any attribute 38 value but returning a pair of iterators pointing to the matched input 39 sequence. It is used to either store the iterator pair into the attribute 40 instance provided by the user or to convert the iterator pair into an 41 attribute as provided by the user. 42 </p> 43<h6> 44<a name="spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.h1"></a> 45 <span class="phrase"><a name="spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.module_headers"></a></span><a class="link" href="assign_to_attribute_from_iterators.html#spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.module_headers">Module 46 Headers</a> 47 </h6> 48<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">spirit</span><span class="special">/</span><span class="identifier">home</span><span class="special">/</span><span class="identifier">qi</span><span class="special">/</span><span class="identifier">detail</span><span class="special">/</span><span class="identifier">assign_to</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 49</pre> 50<p> 51 Also, see <a class="link" href="../../../structure/include.html" title="Include">Include Structure</a>. 52 </p> 53<div class="note"><table border="0" summary="Note"> 54<tr> 55<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../images/note.png"></td> 56<th align="left">Note</th> 57</tr> 58<tr><td align="left" valign="top"><p> 59 This header file does not need to be included directly by any user 60 program as it is normally included by other Spirit header files relying 61 on its content. 62 </p></td></tr> 63</table></div> 64<h6> 65<a name="spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.h2"></a> 66 <span class="phrase"><a name="spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.namespace"></a></span><a class="link" href="assign_to_attribute_from_iterators.html#spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.namespace">Namespace</a> 67 </h6> 68<div class="informaltable"><table class="table"> 69<colgroup><col></colgroup> 70<thead><tr><th> 71 <p> 72 Name 73 </p> 74 </th></tr></thead> 75<tbody><tr><td> 76 <p> 77 <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">traits</span></code> 78 </p> 79 </td></tr></tbody> 80</table></div> 81<h6> 82<a name="spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.h3"></a> 83 <span class="phrase"><a name="spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.synopsis"></a></span><a class="link" href="assign_to_attribute_from_iterators.html#spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.synopsis">Synopsis</a> 84 </h6> 85<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Attrib</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Iterator</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Enable</span><span class="special">></span> 86<span class="keyword">struct</span> <span class="identifier">assign_to_attribute_from_iterators</span> 87<span class="special">{</span> 88 <span class="keyword">static</span> <span class="keyword">void</span> <span class="identifier">call</span><span class="special">(</span><span class="identifier">Iterator</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">Iterator</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">last</span><span class="special">,</span> <span class="identifier">Attrib</span><span class="special">&</span> <span class="identifier">attr</span><span class="special">);</span> 89<span class="special">};</span> 90</pre> 91<h6> 92<a name="spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.h4"></a> 93 <span class="phrase"><a name="spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.template_parameters"></a></span><a class="link" href="assign_to_attribute_from_iterators.html#spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.template_parameters">Template 94 parameters</a> 95 </h6> 96<div class="informaltable"><table class="table"> 97<colgroup> 98<col> 99<col> 100<col> 101</colgroup> 102<thead><tr> 103<th> 104 <p> 105 Parameter 106 </p> 107 </th> 108<th> 109 <p> 110 Description 111 </p> 112 </th> 113<th> 114 <p> 115 Default 116 </p> 117 </th> 118</tr></thead> 119<tbody> 120<tr> 121<td> 122 <p> 123 <code class="computeroutput"><span class="identifier">Attrib</span></code> 124 </p> 125 </td> 126<td> 127 <p> 128 The type, <code class="computeroutput"><span class="identifier">Attrib</span></code> 129 is the type of the attribute as passed in by the user. 130 </p> 131 </td> 132<td> 133 <p> 134 none 135 </p> 136 </td> 137</tr> 138<tr> 139<td> 140 <p> 141 <code class="computeroutput"><span class="identifier">Iterator</span></code> 142 </p> 143 </td> 144<td> 145 <p> 146 The type, <code class="computeroutput"><span class="identifier">Iterator</span></code> 147 is the type of the iterators as produced by the parser. 148 </p> 149 </td> 150<td> 151 <p> 152 none 153 </p> 154 </td> 155</tr> 156<tr> 157<td> 158 <p> 159 <code class="computeroutput"><span class="identifier">Enable</span></code> 160 </p> 161 </td> 162<td> 163 <p> 164 Helper template parameter usable to selectively enable or disable 165 certain specializations of <code class="computeroutput"><span class="identifier">assign_to_attribute_from_value</span></code> 166 utilizing SFINAE (i.e. <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">enable_if</span></code> 167 or <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">disable_if</span></code>). 168 </p> 169 </td> 170<td> 171 <p> 172 <code class="computeroutput"><span class="keyword">void</span></code> 173 </p> 174 </td> 175</tr> 176</tbody> 177</table></div> 178<div class="variablelist"> 179<p class="title"><b>Notation</b></p> 180<dl class="variablelist"> 181<dt><span class="term"><code class="computeroutput"><span class="identifier">Attrib</span></code></span></dt> 182<dd><p> 183 A type to be used as the target to store the attribute value in. 184 </p></dd> 185<dt><span class="term"><code class="computeroutput"><span class="identifier">attr</span></code></span></dt> 186<dd><p> 187 An attribute instance of type <code class="computeroutput"><span class="identifier">Attrib</span></code>. 188 </p></dd> 189<dt><span class="term"><code class="computeroutput"><span class="identifier">Iterator</span></code></span></dt> 190<dd><p> 191 The iterator type used by the parser. This type usually corresponds 192 to the iterators as passed in by the user. 193 </p></dd> 194<dt><span class="term"><code class="computeroutput"><span class="identifier">begin</span></code>, <code class="computeroutput"><span class="identifier">end</span></code></span></dt> 195<dd><p> 196 Iterator instances of type <code class="computeroutput"><span class="identifier">Iterator</span></code> 197 pointing to the begin and the end of the matched input sequence. 198 </p></dd> 199</dl> 200</div> 201<h6> 202<a name="spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.h5"></a> 203 <span class="phrase"><a name="spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.expression_semantics"></a></span><a class="link" href="assign_to_attribute_from_iterators.html#spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.expression_semantics">Expression 204 Semantics</a> 205 </h6> 206<div class="informaltable"><table class="table"> 207<colgroup> 208<col> 209<col> 210</colgroup> 211<thead><tr> 212<th> 213 <p> 214 Expression 215 </p> 216 </th> 217<th> 218 <p> 219 Semantics 220 </p> 221 </th> 222</tr></thead> 223<tbody><tr> 224<td> 225 <p> 226</p> 227<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">assign_to_attribute_from_iterators</span><span class="special"><</span><span class="identifier">Attrib</span><span class="special">,</span> <span class="identifier">Iterator</span><span class="special">>::</span><span class="identifier">call</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span> <span class="identifier">e</span><span class="special">,</span> <span class="identifier">attr</span><span class="special">)</span></pre> 228<p> 229 </p> 230 </td> 231<td> 232 <p> 233 Use the iterators <code class="computeroutput"><span class="identifier">begin</span></code> 234 and <code class="computeroutput"><span class="identifier">end</span></code> to 235 initialize the attribute <code class="computeroutput"><span class="identifier">attr</span></code>. 236 </p> 237 </td> 238</tr></tbody> 239</table></div> 240<h6> 241<a name="spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.h6"></a> 242 <span class="phrase"><a name="spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.predefined_specializations"></a></span><a class="link" href="assign_to_attribute_from_iterators.html#spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.predefined_specializations">Predefined 243 Specializations</a> 244 </h6> 245<div class="informaltable"><table class="table"> 246<colgroup> 247<col> 248<col> 249</colgroup> 250<thead><tr> 251<th> 252 <p> 253 Template Parameters 254 </p> 255 </th> 256<th> 257 <p> 258 Semantics 259 </p> 260 </th> 261</tr></thead> 262<tbody> 263<tr> 264<td> 265 <p> 266 <code class="computeroutput"><span class="identifier">Attrib</span></code>, <code class="computeroutput"><span class="identifier">Iterator</span></code> 267 </p> 268 </td> 269<td> 270 <p> 271 Execute an assignment <code class="computeroutput"><span class="identifier">attr</span> 272 <span class="special">=</span> <span class="identifier">Attrib</span><span class="special">(</span><span class="identifier">begin</span><span class="special">,</span> <span class="identifier">end</span><span class="special">)</span></code>. 273 </p> 274 </td> 275</tr> 276<tr> 277<td> 278 <p> 279 <code class="computeroutput"><span class="identifier">unused_type</span></code>, 280 <code class="computeroutput"><span class="identifier">T</span></code> 281 </p> 282 </td> 283<td> 284 <p> 285 Do nothing. 286 </p> 287 </td> 288</tr> 289</tbody> 290</table></div> 291<h6> 292<a name="spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.h7"></a> 293 <span class="phrase"><a name="spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.when_to_implement"></a></span><a class="link" href="assign_to_attribute_from_iterators.html#spirit.advanced.customize.assign_to.assign_to_attribute_from_iterators.when_to_implement">When 294 to implement</a> 295 </h6> 296<p> 297 The customization point <code class="computeroutput"><span class="identifier">assign_to_attribute_from_iterators</span></code> 298 needs to be implemented for a specific type whenever the default implementation 299 as shown above is not applicable. Examples for this could be that the 300 type <code class="computeroutput"><span class="identifier">Attrib</span></code> is not constructible 301 from the pair of iterators. 302 </p> 303</div> 304<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 305<td align="left"></td> 306<td align="right"><div class="copyright-footer">Copyright © 2001-2011 Joel de Guzman, Hartmut Kaiser<p> 307 Distributed under the Boost Software License, Version 1.0. (See accompanying 308 file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) 309 </p> 310</div></td> 311</tr></table> 312<hr> 313<div class="spirit-nav"> 314<a accesskey="p" href="../assign_to.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../assign_to.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="assign_to_attribute_from_value.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 315</div> 316</body> 317</html> 318
