1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Generator Directive Separating Output Into Columns (columns[])</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="../directive.html" title="Generator Directives"> 9<link rel="prev" href="duplicate.html" title="Generator Directive Duplicating Attributes (duplicate[])"> 10<link rel="next" href="as.html" title="Generator Directives Forcing Atomic Extraction (as<T>, as_string[], as_wstring[])"> 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 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name="spirit.karma.reference.directive.columns"></a><a class="link" href="columns.html" title="Generator Directive Separating Output Into Columns (columns[])">Generator 28 Directive Separating Output Into Columns (<code class="computeroutput"><span class="identifier">columns</span><span class="special">[]</span></code>)</a> 29</h5></div></div></div> 30<h6> 31<a name="spirit.karma.reference.directive.columns.h0"></a> 32 <span class="phrase"><a name="spirit.karma.reference.directive.columns.description"></a></span><a class="link" href="columns.html#spirit.karma.reference.directive.columns.description">Description</a> 33 </h6> 34<p> 35 The <code class="computeroutput"><span class="identifier">columns</span><span class="special">[]</span></code> 36 directive separates the output emitted by the embedded generator by inserting 37 special column separators. 38 </p> 39<h6> 40<a name="spirit.karma.reference.directive.columns.h1"></a> 41 <span class="phrase"><a name="spirit.karma.reference.directive.columns.header"></a></span><a class="link" href="columns.html#spirit.karma.reference.directive.columns.header">Header</a> 42 </h6> 43<pre class="programlisting"><span class="comment">// forwards to <boost/spirit/home/karma/directive/columns.hpp></span> 44<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_columns</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 45</pre> 46<p> 47 Also, see <a class="link" href="../../../structure/include.html" title="Include">Include Structure</a>. 48 </p> 49<div class="informaltable"><table class="table"> 50<colgroup><col></colgroup> 51<thead><tr><th> 52 <p> 53 Name 54 </p> 55 </th></tr></thead> 56<tbody><tr><td> 57 <p> 58 <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">columns</span> <span class="comment">// 59 alias: boost::spirit::karma::columns</span></code> 60 </p> 61 </td></tr></tbody> 62</table></div> 63<h6> 64<a name="spirit.karma.reference.directive.columns.h2"></a> 65 <span class="phrase"><a name="spirit.karma.reference.directive.columns.model_of"></a></span><a class="link" href="columns.html#spirit.karma.reference.directive.columns.model_of">Model of</a> 66 </h6> 67<div class="blockquote"><blockquote class="blockquote"><p> 68 <a class="link" href="../generator_concepts/unarygenerator.html" title="UnaryGenerator"><code class="computeroutput"><span class="identifier">UnaryGenerator</span></code></a> 69 </p></blockquote></div> 70<div class="variablelist"> 71<p class="title"><b>Notation</b></p> 72<dl class="variablelist"> 73<dt><span class="term"><code class="computeroutput"><span class="identifier">a</span></code></span></dt> 74<dd><p> 75 A generator object 76 </p></dd> 77<dt><span class="term"><code class="computeroutput"><span class="identifier">g</span></code></span></dt> 78<dd><p> 79 A generator object, or a <a class="link" href="../basics.html#spirit.karma.reference.basics.lazy_argument">Lazy 80 Argument</a> that evaluates to a generator object, will be used 81 to emit column separators 82 </p></dd> 83<dt><span class="term"><code class="computeroutput"><span class="identifier">A</span></code></span></dt> 84<dd> 85<p> 86 Attribute type of generator <code class="computeroutput"><span class="identifier">a</span></code> 87 </p> 88<p> 89 [<code class="computeroutput"><span class="identifier">num</span></code> 90 </p> 91<p> 92 Numeric literal, any unsigned integer value, or a <a class="link" href="../basics.html#spirit.karma.reference.basics.lazy_argument">Lazy 93 Argument</a> that evaluates to an unsigned integer value defining 94 the number of items to emit in between the column separators 95 </p> 96</dd> 97</dl> 98</div> 99<h6> 100<a name="spirit.karma.reference.directive.columns.h3"></a> 101 <span class="phrase"><a name="spirit.karma.reference.directive.columns.expression_semantics"></a></span><a class="link" href="columns.html#spirit.karma.reference.directive.columns.expression_semantics">Expression 102 Semantics</a> 103 </h6> 104<p> 105 Semantics of an expression is defined only where it differs from, or 106 is not defined in <a class="link" href="../generator_concepts/unarygenerator.html" title="UnaryGenerator"><code class="computeroutput"><span class="identifier">UnaryGenerator</span></code></a>. 107 </p> 108<div class="informaltable"><table class="table"> 109<colgroup> 110<col> 111<col> 112</colgroup> 113<thead><tr> 114<th> 115 <p> 116 Expression 117 </p> 118 </th> 119<th> 120 <p> 121 Semantics 122 </p> 123 </th> 124</tr></thead> 125<tbody> 126<tr> 127<td> 128 <p> 129 <code class="computeroutput"><span class="identifier">columns</span><span class="special">[</span><span class="identifier">a</span><span class="special">]</span></code> 130 </p> 131 </td> 132<td> 133 <p> 134 The <code class="computeroutput"><span class="identifier">columns</span></code> 135 directive invokes a generator after each N-th element of the 136 embedded generator has been emitted. The number of columns 137 is defined by the preprocessor constant <code class="computeroutput"><span class="identifier">BOOST_KARMA_DEFAULT_COLUMNS</span></code>. 138 The column separator used will be <code class="computeroutput"><span class="identifier">karma</span><span class="special">::</span><span class="identifier">eol</span></code>. 139 </p> 140 </td> 141</tr> 142<tr> 143<td> 144 <p> 145 <code class="computeroutput"><span class="identifier">columns</span><span class="special">(</span><span class="identifier">num</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span></code> 146 </p> 147 </td> 148<td> 149 <p> 150 The <code class="computeroutput"><span class="identifier">columns</span></code> 151 directive invokes a generator after each N-th element of the 152 embedded generator has been emitted. The number of columns 153 is defined by the argument to the directive <code class="computeroutput"><span class="identifier">num</span></code>. 154 The column separator used will be <code class="computeroutput"><span class="identifier">karma</span><span class="special">::</span><span class="identifier">eol</span></code>. 155 </p> 156 </td> 157</tr> 158<tr> 159<td> 160 <p> 161 <code class="computeroutput"><span class="identifier">columns</span><span class="special">(</span><span class="identifier">g</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span></code> 162 </p> 163 </td> 164<td> 165 <p> 166 The <code class="computeroutput"><span class="identifier">columns</span></code> 167 directive invokes a generator after each N-th element of the 168 embedded generator has been emitted. The number of columns 169 is defined by the preprocessor constant <code class="computeroutput"><span class="identifier">BOOST_KARMA_DEFAULT_COLUMNS</span></code>. 170 The column separator used will be <code class="computeroutput"><span class="identifier">g</span></code>. 171 </p> 172 </td> 173</tr> 174<tr> 175<td> 176 <p> 177 <code class="computeroutput"><span class="identifier">columns</span><span class="special">(</span><span class="identifier">num</span><span class="special">,</span> 178 <span class="identifier">g</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span></code> 179 </p> 180 </td> 181<td> 182 <p> 183 The <code class="computeroutput"><span class="identifier">columns</span></code> 184 directive invokes a generator after each N-th element of the 185 embedded generator has been emitted. The number of columns 186 is defined by the argument to the directive <code class="computeroutput"><span class="identifier">num</span></code>. 187 The column separator used will be <code class="computeroutput"><span class="identifier">g</span></code>. 188 </p> 189 </td> 190</tr> 191</tbody> 192</table></div> 193<h6> 194<a name="spirit.karma.reference.directive.columns.h4"></a> 195 <span class="phrase"><a name="spirit.karma.reference.directive.columns.attributes"></a></span><a class="link" href="columns.html#spirit.karma.reference.directive.columns.attributes">Attributes</a> 196 </h6> 197<p> 198 See <a class="link" href="../../quick_reference/compound_attribute_rules.html#spirit.karma.quick_reference.compound_attribute_rules.notation">Compound 199 Attribute Notation</a>. 200 </p> 201<div class="informaltable"><table class="table"> 202<colgroup> 203<col> 204<col> 205</colgroup> 206<thead><tr> 207<th> 208 <p> 209 Expression 210 </p> 211 </th> 212<th> 213 <p> 214 Attribute 215 </p> 216 </th> 217</tr></thead> 218<tbody> 219<tr> 220<td> 221 <p> 222 <code class="computeroutput"><span class="identifier">columns</span><span class="special">[</span><span class="identifier">a</span><span class="special">]</span></code> 223 </p> 224 </td> 225<td> 226 <p> 227</p> 228<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">columns</span><span class="special">[</span><span class="identifier">a</span><span class="special">]:</span> <span class="identifier">A</span> 229<span class="identifier">a</span><span class="special">:</span> <span class="identifier">Unused</span> <span class="special">--></span> <span class="identifier">columns</span><span class="special">[</span><span class="identifier">a</span><span class="special">]:</span> <span class="identifier">Unused</span></pre> 230<p> 231 </p> 232 </td> 233</tr> 234<tr> 235<td> 236 <p> 237 <code class="computeroutput"><span class="identifier">columns</span><span class="special">(</span><span class="identifier">num</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span></code> 238 </p> 239 </td> 240<td> 241 <p> 242</p> 243<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">columns</span><span class="special">(</span><span class="identifier">num</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]:</span> <span class="identifier">A</span> 244<span class="identifier">a</span><span class="special">:</span> <span class="identifier">Unused</span> <span class="special">--></span> <span class="identifier">columns</span><span class="special">(</span><span class="identifier">num</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]:</span> <span class="identifier">Unused</span></pre> 245<p> 246 </p> 247 </td> 248</tr> 249<tr> 250<td> 251 <p> 252 <code class="computeroutput"><span class="identifier">columns</span><span class="special">(</span><span class="identifier">g</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span></code> 253 </p> 254 </td> 255<td> 256 <p> 257</p> 258<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">columns</span><span class="special">(</span><span class="identifier">g</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]:</span> <span class="identifier">A</span> 259<span class="identifier">a</span><span class="special">:</span> <span class="identifier">Unused</span> <span class="special">--></span> <span class="identifier">columns</span><span class="special">(</span><span class="identifier">g</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]:</span> <span class="identifier">Unused</span></pre> 260<p> 261 </p> 262 </td> 263</tr> 264<tr> 265<td> 266 <p> 267 <code class="computeroutput"><span class="identifier">columns</span><span class="special">(</span><span class="identifier">num</span><span class="special">,</span> 268 <span class="identifier">g</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span></code> 269 </p> 270 </td> 271<td> 272 <p> 273</p> 274<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">columns</span><span class="special">(</span><span class="identifier">num</span><span class="special">,</span> <span class="identifier">g</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]:</span> <span class="identifier">A</span> 275<span class="identifier">a</span><span class="special">:</span> <span class="identifier">Unused</span> <span class="special">--></span> <span class="identifier">columns</span><span class="special">(</span><span class="identifier">num</span><span class="special">,</span> <span class="identifier">g</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]:</span> <span class="identifier">Unused</span></pre> 276<p> 277 </p> 278 </td> 279</tr> 280</tbody> 281</table></div> 282<h6> 283<a name="spirit.karma.reference.directive.columns.h5"></a> 284 <span class="phrase"><a name="spirit.karma.reference.directive.columns.complexity"></a></span><a class="link" href="columns.html#spirit.karma.reference.directive.columns.complexity">Complexity</a> 285 </h6> 286<div class="blockquote"><blockquote class="blockquote"><p> 287 The overall complexity of the <code class="computeroutput"><span class="identifier">columns</span></code> 288 generator directive depends on the complexity of the embedded generator. 289 The complexity of the <code class="computeroutput"><span class="identifier">columns</span></code> 290 generator directive itself is O(N), where <code class="computeroutput"><span class="identifier">N</span></code> 291 is the number of inserted column separators. 292 </p></blockquote></div> 293<h6> 294<a name="spirit.karma.reference.directive.columns.h6"></a> 295 <span class="phrase"><a name="spirit.karma.reference.directive.columns.example"></a></span><a class="link" href="columns.html#spirit.karma.reference.directive.columns.example">Example</a> 296 </h6> 297<div class="note"><table border="0" summary="Note"> 298<tr> 299<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../images/note.png"></td> 300<th align="left">Note</th> 301</tr> 302<tr><td align="left" valign="top"><p> 303 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> 304 section. 305 </p></td></tr> 306</table></div> 307<p> 308 Some includes: 309 </p> 310<p> 311</p> 312<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> 313<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> 314<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> 315<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> 316<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> 317<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> 318<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">string</span><span class="special">></span> 319</pre> 320<p> 321 </p> 322<p> 323 Some using declarations: 324 </p> 325<p> 326</p> 327<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> 328<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">columns</span><span class="special">;</span> 329<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">space</span><span class="special">;</span> 330</pre> 331<p> 332 </p> 333<p> 334 Basic usage of the <code class="computeroutput"><span class="identifier">columns</span></code> 335 generators: 336 </p> 337<p> 338</p> 339<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">v</span><span class="special">;</span> 340<span class="identifier">v</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="number">1.0</span><span class="special">);</span> 341<span class="identifier">v</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="number">2.0</span><span class="special">);</span> 342<span class="identifier">v</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="number">3.0</span><span class="special">);</span> 343<span class="identifier">test_generator_attr</span><span class="special">(</span><span class="string">"1.0\n2.0\n3.0\n"</span><span class="special">,</span> <span class="identifier">columns</span><span class="special">(</span><span class="number">1</span><span class="special">)[*</span><span class="identifier">double_</span><span class="special">],</span> <span class="identifier">v</span><span class="special">);</span> 344<span class="identifier">test_generator_attr_delim</span><span class="special">(</span><span class="string">"1.0 2.0 \n3.0 \n"</span><span class="special">,</span> <span class="identifier">columns</span><span class="special">(</span><span class="number">2</span><span class="special">)[*</span><span class="identifier">double_</span><span class="special">],</span> <span class="identifier">space</span><span class="special">,</span> <span class="identifier">v</span><span class="special">);</span> 345</pre> 346<p> 347 </p> 348</div> 349<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 350<td align="left"></td> 351<td align="right"><div class="copyright-footer">Copyright © 2001-2011 Joel de Guzman, Hartmut Kaiser<p> 352 Distributed under the Boost Software License, Version 1.0. (See accompanying 353 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>) 354 </p> 355</div></td> 356</tr></table> 357<hr> 358<div class="spirit-nav"> 359<a accesskey="p" href="duplicate.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../directive.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="as.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 360</div> 361</body> 362</html> 363
