1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Sequence Generator (a << b)</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="../operator.html" title="Generator Operators"> 9<link rel="prev" href="../operator.html" title="Generator Operators"> 10<link rel="next" href="alternative.html" title="Alternative Generator (a | b)"> 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="../operator.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../operator.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="alternative.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.karma.reference.operator.sequence"></a><a class="link" href="sequence.html" title="Sequence Generator (a << b)">Sequence 28 Generator (<code class="computeroutput"><span class="identifier">a</span> <span class="special"><<</span> 29 <span class="identifier">b</span></code>)</a> 30</h5></div></div></div> 31<h6> 32<a name="spirit.karma.reference.operator.sequence.h0"></a> 33 <span class="phrase"><a name="spirit.karma.reference.operator.sequence.description"></a></span><a class="link" href="sequence.html#spirit.karma.reference.operator.sequence.description">Description</a> 34 </h6> 35<p> 36 Generator sequences are used to consecutively combine different, more 37 primitive generators. All generators in a sequence are invoked from left 38 to right as long as they succeed. 39 </p> 40<h6> 41<a name="spirit.karma.reference.operator.sequence.h1"></a> 42 <span class="phrase"><a name="spirit.karma.reference.operator.sequence.header"></a></span><a class="link" href="sequence.html#spirit.karma.reference.operator.sequence.header">Header</a> 43 </h6> 44<pre class="programlisting"><span class="comment">// forwards to <boost/spirit/home/karma/operator/sequence.hpp></span> 45<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">include</span><span class="special">/</span><span class="identifier">karma_sequence</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 46</pre> 47<p> 48 Also, see <a class="link" href="../../../structure/include.html" title="Include">Include Structure</a>. 49 </p> 50<h6> 51<a name="spirit.karma.reference.operator.sequence.h2"></a> 52 <span class="phrase"><a name="spirit.karma.reference.operator.sequence.model_of"></a></span><a class="link" href="sequence.html#spirit.karma.reference.operator.sequence.model_of">Model of</a> 53 </h6> 54<div class="blockquote"><blockquote class="blockquote"><p> 55 <a class="link" href="../generator_concepts/narygenerator.html" title="NaryGenerator"><code class="computeroutput"><span class="identifier">NaryGenerator</span></code></a> 56 </p></blockquote></div> 57<h6> 58<a name="spirit.karma.reference.operator.sequence.h3"></a> 59 <span class="phrase"><a name="spirit.karma.reference.operator.sequence.expression_semantics"></a></span><a class="link" href="sequence.html#spirit.karma.reference.operator.sequence.expression_semantics">Expression 60 Semantics</a> 61 </h6> 62<p> 63 Semantics of an expression is defined only where it differs from, or 64 is not defined in <a class="link" href="../generator_concepts/narygenerator.html" title="NaryGenerator"><code class="computeroutput"><span class="identifier">NaryGenerator</span></code></a>. 65 </p> 66<div class="informaltable"><table class="table"> 67<colgroup> 68<col> 69<col> 70</colgroup> 71<thead><tr> 72<th> 73 <p> 74 Expression 75 </p> 76 </th> 77<th> 78 <p> 79 Semantics 80 </p> 81 </th> 82</tr></thead> 83<tbody><tr> 84<td> 85 <p> 86 <code class="computeroutput"><span class="identifier">a</span> <span class="special"><<</span> 87 <span class="identifier">b</span></code> 88 </p> 89 </td> 90<td> 91 <p> 92 The generators <code class="computeroutput"><span class="identifier">a</span></code> 93 and <code class="computeroutput"><span class="identifier">b</span></code> are executed 94 sequentially from left to right and as long as they succeed. 95 A failed generator stops the execution of the entire sequence 96 and makes the sequence fail as well. 97 </p> 98 </td> 99</tr></tbody> 100</table></div> 101<p> 102 It is important to note, that sequences don't perform any buffering of 103 the output generated by its elements. That means that any failing sequence 104 might have already generated some output, which is <span class="emphasis"><em>not</em></span> 105 rolled back. 106 </p> 107<div class="tip"><table border="0" summary="Tip"> 108<tr> 109<td rowspan="2" align="center" valign="top" width="25"><img alt="[Tip]" src="../../../../images/tip.png"></td> 110<th align="left">Tip</th> 111</tr> 112<tr><td align="left" valign="top"> 113<p> 114 The simplest way to force a sequence to behave as if it did buffering 115 is to wrap it into a buffering directive (see <a class="link" href="../directive/buffer.html" title="Generator Directive for Temporary Output Buffering (buffer[])"><code class="computeroutput"><span class="identifier">buffer</span></code></a>): 116 </p> 117<p> 118</p> 119<pre class="programlisting"><span class="identifier">buffer</span><span class="special">[</span><span class="identifier">a</span> <span class="special"><<</span> <span class="identifier">b</span> <span class="special"><<</span> <span class="identifier">c</span><span class="special">]</span></pre> 120<p> 121 </p> 122<p> 123 which will <span class="emphasis"><em>not</em></span> generate any output in case of 124 a failing sequence. 125 </p> 126</td></tr> 127</table></div> 128<h6> 129<a name="spirit.karma.reference.operator.sequence.h4"></a> 130 <span class="phrase"><a name="spirit.karma.reference.operator.sequence.attributes"></a></span><a class="link" href="sequence.html#spirit.karma.reference.operator.sequence.attributes">Attributes</a> 131 </h6> 132<p> 133 See <a class="link" href="../../quick_reference/compound_attribute_rules.html#spirit.karma.quick_reference.compound_attribute_rules.notation">Compound 134 Attribute Notation</a>. 135 </p> 136<div class="informaltable"><table class="table"> 137<colgroup> 138<col> 139<col> 140</colgroup> 141<thead><tr> 142<th> 143 <p> 144 Expression 145 </p> 146 </th> 147<th> 148 <p> 149 Attribute 150 </p> 151 </th> 152</tr></thead> 153<tbody><tr> 154<td> 155 <p> 156 <code class="computeroutput"><span class="identifier">a</span> <span class="special"><<</span> 157 <span class="identifier">b</span></code> (sequence) 158 </p> 159 </td> 160<td> 161 <p> 162</p> 163<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">a</span><span class="special">:</span> <span class="identifier">A</span><span class="special">,</span> <span class="identifier">b</span><span class="special">:</span> <span class="identifier">B</span> <span class="special">--></span> <span class="special">(</span><span class="identifier">a</span> <span class="special"><<</span> <span class="identifier">b</span><span class="special">):</span> <span class="identifier">tuple</span><span class="special"><</span><span class="identifier">A</span><span class="special">,</span> <span class="identifier">B</span><span class="special">></span> 164<span class="identifier">a</span><span class="special">:</span> <span class="identifier">A</span><span class="special">,</span> <span class="identifier">b</span><span class="special">:</span> <span class="identifier">Unused</span> <span class="special">--></span> <span class="special">(</span><span class="identifier">a</span> <span class="special"><<</span> <span class="identifier">b</span><span class="special">):</span> <span class="identifier">A</span> 165<span class="identifier">a</span><span class="special">:</span> <span class="identifier">Unused</span><span class="special">,</span> <span class="identifier">b</span><span class="special">:</span> <span class="identifier">B</span> <span class="special">--></span> <span class="special">(</span><span class="identifier">a</span> <span class="special"><<</span> <span class="identifier">b</span><span class="special">):</span> <span class="identifier">B</span> 166<span class="identifier">a</span><span class="special">:</span> <span class="identifier">Unused</span><span class="special">,</span> <span class="identifier">b</span><span class="special">:</span> <span class="identifier">Unused</span> <span class="special">--></span> <span class="special">(</span><span class="identifier">a</span> <span class="special"><<</span> <span class="identifier">b</span><span class="special">):</span> <span class="identifier">Unused</span> 167 168<span class="identifier">a</span><span class="special">:</span> <span class="identifier">A</span><span class="special">,</span> <span class="identifier">b</span><span class="special">:</span> <span class="identifier">A</span> <span class="special">--></span> <span class="special">(</span><span class="identifier">a</span> <span class="special"><<</span> <span class="identifier">b</span><span class="special">):</span> <span class="identifier">vector</span><span class="special"><</span><span class="identifier">A</span><span class="special">></span> 169<span class="identifier">a</span><span class="special">:</span> <span class="identifier">vector</span><span class="special"><</span><span class="identifier">A</span><span class="special">>,</span> <span class="identifier">b</span><span class="special">:</span> <span class="identifier">A</span> <span class="special">--></span> <span class="special">(</span><span class="identifier">a</span> <span class="special"><<</span> <span class="identifier">b</span><span class="special">):</span> <span class="identifier">vector</span><span class="special"><</span><span class="identifier">A</span><span class="special">></span> 170<span class="identifier">a</span><span class="special">:</span> <span class="identifier">A</span><span class="special">,</span> <span class="identifier">b</span><span class="special">:</span> <span class="identifier">vector</span><span class="special"><</span><span class="identifier">A</span><span class="special">></span> <span class="special">--></span> <span class="special">(</span><span class="identifier">a</span> <span class="special"><<</span> <span class="identifier">b</span><span class="special">):</span> <span class="identifier">vector</span><span class="special"><</span><span class="identifier">A</span><span class="special">></span> 171<span class="identifier">a</span><span class="special">:</span> <span class="identifier">vector</span><span class="special"><</span><span class="identifier">A</span><span class="special">>,</span> <span class="identifier">b</span><span class="special">:</span> <span class="identifier">vector</span><span class="special"><</span><span class="identifier">A</span><span class="special">></span> <span class="special">--></span> <span class="special">(</span><span class="identifier">a</span> <span class="special"><<</span> <span class="identifier">b</span><span class="special">):</span> <span class="identifier">vector</span><span class="special"><</span><span class="identifier">A</span><span class="special">></span></pre> 172<p> 173 </p> 174 </td> 175</tr></tbody> 176</table></div> 177<div class="important"><table border="0" summary="Important"> 178<tr> 179<td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="../../../../images/important.png"></td> 180<th align="left">Important</th> 181</tr> 182<tr><td align="left" valign="top"> 183<p> 184 The table above uses <code class="computeroutput"><span class="identifier">tuple</span><span class="special"><</span><span class="identifier">A</span><span class="special">,</span> <span class="identifier">B</span><span class="special">></span></code> and <code class="computeroutput"><span class="identifier">vector</span><span class="special"><</span><span class="identifier">A</span><span class="special">></span></code> as placeholders only. 185 </p> 186<p> 187 The notation <code class="computeroutput"><span class="identifier">tuple</span><span class="special"><</span><span class="identifier">A</span><span class="special">,</span> <span class="identifier">B</span><span class="special">></span></code> stands for <span class="emphasis"><em>any fusion 188 sequence of two elements</em></span>, where <code class="computeroutput"><span class="identifier">A</span></code> 189 is the type of its first element and <code class="computeroutput"><span class="identifier">B</span></code> 190 is the type of its second element. 191 </p> 192<p> 193 The notation of <code class="computeroutput"><span class="identifier">vector</span><span class="special"><</span><span class="identifier">A</span><span class="special">></span></code> stands for <span class="emphasis"><em>any STL container</em></span> 194 holding elements of type <code class="computeroutput"><span class="identifier">A</span></code>. 195 </p> 196</td></tr> 197</table></div> 198<p> 199 The attribute composition and propagation rules as shown in the table 200 above make sequences somewhat special as they can operate in two modes 201 if all elements have the same attribute type: consuming fusion sequences 202 and consuming STL containers. The selected mode depends on the type of 203 the attribute supplied. 204 </p> 205<h6> 206<a name="spirit.karma.reference.operator.sequence.h5"></a> 207 <span class="phrase"><a name="spirit.karma.reference.operator.sequence.complexity"></a></span><a class="link" href="sequence.html#spirit.karma.reference.operator.sequence.complexity">Complexity</a> 208 </h6> 209<div class="blockquote"><blockquote class="blockquote"><p> 210 The overall complexity of the sequence generator is defined by the 211 sum of the complexities of its elements. The complexity of the sequence 212 itself is O(N), where N is the number of elements in the sequence. 213 </p></blockquote></div> 214<h6> 215<a name="spirit.karma.reference.operator.sequence.h6"></a> 216 <span class="phrase"><a name="spirit.karma.reference.operator.sequence.example"></a></span><a class="link" href="sequence.html#spirit.karma.reference.operator.sequence.example">Example</a> 217 </h6> 218<div class="note"><table border="0" summary="Note"> 219<tr> 220<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../images/note.png"></td> 221<th align="left">Note</th> 222</tr> 223<tr><td align="left" valign="top"><p> 224 The test harness for the example(s) below is presented in the <a class="link" href="../basics.html#spirit.karma.reference.basics.examples">Basics Examples</a> 225 section. 226 </p></td></tr> 227</table></div> 228<p> 229 Some includes: 230 </p> 231<p> 232</p> 233<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">include</span><span class="special">/</span><span class="identifier">karma</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 234<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">include</span><span class="special">/</span><span class="identifier">support_utree</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 235<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">include</span><span class="special">/</span><span class="identifier">phoenix_core</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 236<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">include</span><span class="special">/</span><span class="identifier">phoenix_operator</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 237<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">std_pair</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 238<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> 239<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">string</span><span class="special">></span> 240</pre> 241<p> 242 </p> 243<p> 244 Some using declarations: 245 </p> 246<p> 247</p> 248<pre class="programlisting"><span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">karma</span><span class="special">::</span><span class="identifier">double_</span><span class="special">;</span> 249</pre> 250<p> 251 </p> 252<p> 253 Basic usage of a sequence: 254 </p> 255<p> 256</p> 257<pre class="programlisting"><span class="identifier">test_generator_attr</span><span class="special">(</span><span class="string">"1.0,2.0"</span><span class="special">,</span> <span class="identifier">double_</span> <span class="special"><<</span> <span class="char">','</span> <span class="special"><<</span> <span class="identifier">double_</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">make_pair</span><span class="special">(</span><span class="number">1.0</span><span class="special">,</span> <span class="number">2.0</span><span class="special">));</span> 258</pre> 259<p> 260 </p> 261</div> 262<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 263<td align="left"></td> 264<td align="right"><div class="copyright-footer">Copyright © 2001-2011 Joel de Guzman, Hartmut Kaiser<p> 265 Distributed under the Boost Software License, Version 1.0. (See accompanying 266 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>) 267 </p> 268</div></td> 269</tr></table> 270<hr> 271<div class="spirit-nav"> 272<a accesskey="p" href="../operator.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../operator.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="alternative.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 273</div> 274</body> 275</html> 276
