1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Number List - Printing Numbers From a std::vector</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="../tutorials.html" title="Tutorials"> 9<link rel="prev" href="karma_adapted_complex.html" title="Complex - Fully Integrated"> 10<link rel="next" href="num_matrix.html" title="Matrix of Numbers - Printing Numbers From a Matrix"> 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="karma_adapted_complex.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../tutorials.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="num_matrix.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h4 class="title"> 27<a name="spirit.karma.tutorials.num_list"></a><a class="link" href="num_list.html" title="Number List - Printing Numbers From a std::vector">Number List - Printing 28 Numbers From a std::vector</a> 29</h4></div></div></div> 30<h6> 31<a name="spirit.karma.tutorials.num_list.h0"></a> 32 <span class="phrase"><a name="spirit.karma.tutorials.num_list.using_the_list_operator"></a></span><a class="link" href="num_list.html#spirit.karma.tutorials.num_list.using_the_list_operator">Using 33 the List Operator</a> 34 </h6> 35<p> 36 The C++ Standard library lacks an important feature, namely the support 37 for any formatted output of containers. Sure, it's fairly easy to write 38 a custom routine to output a specific container, but doing so over and 39 over again is tedious at best. In this section we will demonstrate some 40 more of the capabilities of <span class="emphasis"><em>Spirit.Karma</em></span> for generating 41 output from arbitrary STL containers. We will build on the example presented 42 in an earlier section (see <a class="link" href="warming_up.html" title="Warming up">Warming 43 Up</a>). 44 </p> 45<p> 46 The full source code of the example shown in this section can be found 47 here: <a href="../../../../../example/karma/num_list2.cpp" target="_top">num_list2.cpp</a>. 48 </p> 49<p> 50 This time we take advantage of Karma's <a class="link" href="../reference/operator/list.html" title="List Generator (a % b)">List 51 (<code class="computeroutput"><span class="special">%</span></code>)</a> operator. The semantics 52 of the list operator are fully equivalent to the semantics of the sequence 53 we used before. The generator expression 54 </p> 55<pre class="programlisting"><span class="identifier">double_</span> <span class="special"><<</span> <span class="special">*(</span><span class="char">','</span> <span class="special"><<</span> <span class="identifier">double_</span><span class="special">)</span> 56</pre> 57<p> 58 is semantically equivalent to the generator expression 59 </p> 60<pre class="programlisting"><span class="identifier">double_</span> <span class="special">%</span> <span class="char">','</span> 61</pre> 62<p> 63 simplifying the overall code. The list operator's attribute is compatible 64 with any STL container as well. For a change we use a <code class="computeroutput"><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></code> instead of the <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">list</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span></code> we used before. Additionally, the routine 65 <code class="computeroutput"><span class="identifier">generate_numbers</span></code> takes 66 the container as a template parameter, so it will now work with any STL 67 container holding <code class="computeroutput"><span class="keyword">double</span></code> numbers. 68 </p> 69<p> 70</p> 71<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">OutputIterator</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Container</span><span class="special">></span> 72<span class="keyword">bool</span> <span class="identifier">generate_numbers</span><span class="special">(</span><span class="identifier">OutputIterator</span><span class="special">&</span> <span class="identifier">sink</span><span class="special">,</span> <span class="identifier">Container</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span><span class="special">)</span> 73<span class="special">{</span> 74 <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> 75 <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">generate_delimited</span><span class="special">;</span> 76 <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">ascii</span><span class="special">::</span><span class="identifier">space</span><span class="special">;</span> 77 78 <span class="keyword">bool</span> <span class="identifier">r</span> <span class="special">=</span> <span class="identifier">generate_delimited</span><span class="special">(</span> 79 <span class="identifier">sink</span><span class="special">,</span> <span class="comment">// destination: output iterator</span> 80 <span class="identifier">double_</span> <span class="special">%</span> <span class="char">','</span><span class="special">,</span> <span class="comment">// the generator</span> 81 <span class="identifier">space</span><span class="special">,</span> <span class="comment">// the delimiter-generator</span> 82 <span class="identifier">v</span> <span class="comment">// the data to output </span> 83 <span class="special">);</span> 84 <span class="keyword">return</span> <span class="identifier">r</span><span class="special">;</span> 85<span class="special">}</span> 86</pre> 87<p> 88 </p> 89<div class="note"><table border="0" summary="Note"> 90<tr> 91<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../images/note.png"></td> 92<th align="left">Note</th> 93</tr> 94<tr><td align="left" valign="top"><p> 95 Despite the container being a template parameter, the <span class="emphasis"><em>Spirit.Karma</em></span> 96 formatting expression (<code class="computeroutput"><span class="identifier">double_</span> 97 <span class="special">%</span> <span class="char">','</span></code>) 98 does not depend on the actual type of the passed container. The only 99 precondition to be met here is that the elements stored in the container 100 have to be convertible to <code class="computeroutput"><span class="keyword">double</span></code>. 101 </p></td></tr> 102</table></div> 103<h6> 104<a name="spirit.karma.tutorials.num_list.h1"></a> 105 <span class="phrase"><a name="spirit.karma.tutorials.num_list.generate_output_from_arbitrary_data"></a></span><a class="link" href="num_list.html#spirit.karma.tutorials.num_list.generate_output_from_arbitrary_data">Generate 106 Output from Arbitrary Data</a> 107 </h6> 108<p> 109 The output routine developed above is still not generically usable for 110 all types of STL containers and for arbitrary elements stored in them. 111 In order to be usable the items stored in the container still need to be 112 convertible to a <code class="computeroutput"><span class="keyword">double</span></code>. Fortunately 113 <span class="emphasis"><em>Spirit.Karma</em></span> is capable to output arbitrary data types 114 while using the same format description expression. It implements the 115 <a class="link" href="../reference/stream/stream.html" title="Stream Generators (stream, wstream, etc.)"><code class="computeroutput"><span class="identifier">stream</span></code></a> 116 generators which are able to consume any attribute type as long as a matching 117 standard streaming operator is defined. I.e. for any attribute type <code class="computeroutput"><span class="identifier">Attrib</span></code> a function: 118 </p> 119<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span><span class="special">&</span> <span class="keyword">operator</span><span class="special"><<</span> <span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span><span class="special">&,</span> <span class="identifier">Attrib</span> <span class="keyword">const</span><span class="special">&);</span> 120</pre> 121<p> 122 needs to be available. The <a class="link" href="../reference/stream/stream.html" title="Stream Generators (stream, wstream, etc.)"><code class="computeroutput"><span class="identifier">stream</span></code></a> generator will use the 123 standard streaming operator to generate the output. 124 </p> 125<p> 126 The following example modifies the code shown above to utilize the <a class="link" href="../reference/stream/stream.html" title="Stream Generators (stream, wstream, etc.)"><code class="computeroutput"><span class="identifier">stream</span></code></a> 127 operator, which makes it compatible with almost any data type. We implement 128 a custom data type <code class="computeroutput"><span class="identifier">complex</span></code> 129 to demonstrate this. The example shows how it is possible to integrate 130 this (or any other) custom data type into the <span class="emphasis"><em>Spirit.Karma</em></span> 131 generator framework. 132 </p> 133<p> 134 This is the custom data structure together with the required standard streaming 135 operator: 136 </p> 137<p> 138</p> 139<pre class="programlisting"><span class="comment">// a simple complex number representation z = a + bi</span> 140<span class="keyword">struct</span> <span class="identifier">complex</span> 141<span class="special">{</span> 142 <span class="identifier">complex</span> <span class="special">(</span><span class="keyword">double</span> <span class="identifier">a</span><span class="special">,</span> <span class="keyword">double</span> <span class="identifier">b</span> <span class="special">=</span> <span class="number">0.0</span><span class="special">)</span> <span class="special">:</span> <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> 143 144 <span class="keyword">double</span> <span class="identifier">a</span><span class="special">;</span> 145 <span class="keyword">double</span> <span class="identifier">b</span><span class="special">;</span> 146<span class="special">};</span> 147 148<span class="comment">// the streaming operator for the type complex</span> 149<span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span><span class="special">&</span> 150<span class="keyword">operator</span><span class="special"><<</span> <span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span><span class="special">&</span> <span class="identifier">os</span><span class="special">,</span> <span class="identifier">complex</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">z</span><span class="special">)</span> 151<span class="special">{</span> 152 <span class="identifier">os</span> <span class="special"><<</span> <span class="string">"{"</span> <span class="special"><<</span> <span class="identifier">z</span><span class="special">.</span><span class="identifier">a</span> <span class="special"><<</span> <span class="string">","</span> <span class="special"><<</span> <span class="identifier">z</span><span class="special">.</span><span class="identifier">b</span> <span class="special"><<</span> <span class="string">"}"</span><span class="special">;</span> 153 <span class="keyword">return</span> <span class="identifier">os</span><span class="special">;</span> 154<span class="special">}</span> 155</pre> 156<p> 157 </p> 158<p> 159 And this is the actual call to generate the output from a vector of those. 160 This time we interleave the generated output with newline breaks (see 161 <a class="link" href="../reference/auxiliary/eol.html" title="End of Line Generator (eol)"><code class="computeroutput"><span class="identifier">eol</span></code></a>), 162 putting each complex number onto a separate line: 163 </p> 164<p> 165</p> 166<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">OutputIterator</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Container</span><span class="special">></span> 167<span class="keyword">bool</span> <span class="identifier">generate_numbers</span><span class="special">(</span><span class="identifier">OutputIterator</span><span class="special">&</span> <span class="identifier">sink</span><span class="special">,</span> <span class="identifier">Container</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span><span class="special">)</span> 168<span class="special">{</span> 169 <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">stream</span><span class="special">;</span> 170 <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">generate</span><span class="special">;</span> 171 <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">eol</span><span class="special">;</span> 172 173 <span class="keyword">bool</span> <span class="identifier">r</span> <span class="special">=</span> <span class="identifier">generate</span><span class="special">(</span> 174 <span class="identifier">sink</span><span class="special">,</span> <span class="comment">// destination: output iterator</span> 175 <span class="identifier">stream</span> <span class="special">%</span> <span class="identifier">eol</span><span class="special">,</span> <span class="comment">// the generator</span> 176 <span class="identifier">v</span> <span class="comment">// the data to output </span> 177 <span class="special">);</span> 178 <span class="keyword">return</span> <span class="identifier">r</span><span class="special">;</span> 179<span class="special">}</span> 180</pre> 181<p> 182 </p> 183<p> 184 The code shown is fully generic and can be used with any STL container 185 as long as the data items stored in that container implement the standard 186 streaming operator. 187 </p> 188<p> 189 The full source code of the example presented in this section can be found 190 here: <a href="../../../../../example/karma/num_list3.cpp" target="_top">num_list3.cpp</a>. 191 </p> 192</div> 193<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 194<td align="left"></td> 195<td align="right"><div class="copyright-footer">Copyright © 2001-2011 Joel de Guzman, Hartmut Kaiser<p> 196 Distributed under the Boost Software License, Version 1.0. (See accompanying 197 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>) 198 </p> 199</div></td> 200</tr></table> 201<hr> 202<div class="spirit-nav"> 203<a accesskey="p" href="karma_adapted_complex.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../tutorials.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="num_matrix.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 204</div> 205</body> 206</html> 207
