1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Sum - adding numbers</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="complex___our_first_complex_parser.html" title="Complex - Our first complex parser"> 10<link rel="next" href="number_list___stuffing_numbers_into_a_std__vector.html" title="Number List - stuffing numbers into a std::vector"> 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="complex___our_first_complex_parser.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="number_list___stuffing_numbers_into_a_std__vector.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.qi.tutorials.sum___adding_numbers"></a><a class="link" href="sum___adding_numbers.html" title="Sum - adding numbers">Sum - adding 28 numbers</a> 29</h4></div></div></div> 30<p> 31 Here's a parser that sums a comma-separated list of numbers. 32 </p> 33<p> 34 Ok we've glossed over some details in our previous examples. First, our 35 includes: 36 </p> 37<p> 38</p> 39<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">qi</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 40<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> 41<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> 42<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> 43<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">string</span><span class="special">></span> 44</pre> 45<p> 46 </p> 47<p> 48 Then some using directives: 49 </p> 50<p> 51</p> 52<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">qi</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">qi</span><span class="special">;</span> 53<span class="keyword">namespace</span> <span class="identifier">ascii</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">ascii</span><span class="special">;</span> 54<span class="keyword">namespace</span> <span class="identifier">phoenix</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">phoenix</span><span class="special">;</span> 55 56<span class="keyword">using</span> <span class="identifier">qi</span><span class="special">::</span><span class="identifier">double_</span><span class="special">;</span> 57<span class="keyword">using</span> <span class="identifier">qi</span><span class="special">::</span><span class="identifier">_1</span><span class="special">;</span> 58<span class="keyword">using</span> <span class="identifier">ascii</span><span class="special">::</span><span class="identifier">space</span><span class="special">;</span> 59<span class="keyword">using</span> <span class="identifier">phoenix</span><span class="special">::</span><span class="identifier">ref</span><span class="special">;</span> 60</pre> 61<p> 62 </p> 63<div class="informaltable"><table class="table"> 64<colgroup> 65<col> 66<col> 67</colgroup> 68<thead><tr> 69<th> 70 <p> 71 Namespace 72 </p> 73 </th> 74<th> 75 <p> 76 Description 77 </p> 78 </th> 79</tr></thead> 80<tbody> 81<tr> 82<td> 83 <p> 84 boost::phoenix 85 </p> 86 </td> 87<td> 88 <p> 89 All of phoenix 90 </p> 91 </td> 92</tr> 93<tr> 94<td> 95 <p> 96 boost::spirit 97 </p> 98 </td> 99<td> 100 <p> 101 All of spirit 102 </p> 103 </td> 104</tr> 105<tr> 106<td> 107 <p> 108 boost::spirit::qi 109 </p> 110 </td> 111<td> 112 <p> 113 All of spirit.qi 114 </p> 115 </td> 116</tr> 117<tr> 118<td> 119 <p> 120 boost::spirit::ascii 121 </p> 122 </td> 123<td> 124 <p> 125 ASCII version of <code class="computeroutput"><span class="identifier">char_</span></code> 126 and all char related parsers. Other encodings are also provided 127 (e.g. also an ISO8859.1) 128 </p> 129 </td> 130</tr> 131<tr> 132<td> 133 <p> 134 boost::spirit::arg_names 135 </p> 136 </td> 137<td> 138 <p> 139 Special phoenix placeholders for spirit 140 </p> 141 </td> 142</tr> 143</tbody> 144</table></div> 145<div class="note"><table border="0" summary="Note"> 146<tr> 147<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../images/note.png"></td> 148<th align="left">Note</th> 149</tr> 150<tr><td align="left" valign="top"><p> 151 If you feel uneasy with using whole namespaces, feel free to qualify 152 your code, use namespace aliases, etc. For the purpose of this tutorial, 153 we will be presenting unqualified names for both Spirit and <a href="../../../../../../../libs/phoenix/doc/html/index.html" target="_top">Boost.Phoenix</a>. 154 No worries, we will always present the full working code, so you won't 155 get lost. In fact, all examples in this tutorial have a corresponding 156 cpp file that QuickBook (the documentation tool we are using) imports 157 in here as code snippets. 158 </p></td></tr> 159</table></div> 160<p> 161 Now the actual parser: 162 </p> 163<p> 164</p> 165<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Iterator</span><span class="special">></span> 166<span class="keyword">bool</span> <span class="identifier">adder</span><span class="special">(</span><span class="identifier">Iterator</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">Iterator</span> <span class="identifier">last</span><span class="special">,</span> <span class="keyword">double</span><span class="special">&</span> <span class="identifier">n</span><span class="special">)</span> 167<span class="special">{</span> 168 <span class="keyword">bool</span> <span class="identifier">r</span> <span class="special">=</span> <span class="identifier">qi</span><span class="special">::</span><span class="identifier">phrase_parse</span><span class="special">(</span><span class="identifier">first</span><span class="special">,</span> <span class="identifier">last</span><span class="special">,</span> 169 170 <span class="comment">// Begin grammar</span> 171 <span class="special">(</span> 172 <span class="identifier">double_</span><span class="special">[</span><span class="identifier">ref</span><span class="special">(</span><span class="identifier">n</span><span class="special">)</span> <span class="special">=</span> <span class="identifier">_1</span><span class="special">]</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><span class="identifier">ref</span><span class="special">(</span><span class="identifier">n</span><span class="special">)</span> <span class="special">+=</span> <span class="identifier">_1</span><span class="special">])</span> 173 <span class="special">)</span> 174 <span class="special">,</span> 175 <span class="comment">// End grammar</span> 176 177 <span class="identifier">space</span><span class="special">);</span> 178 179 <span class="keyword">if</span> <span class="special">(</span><span class="identifier">first</span> <span class="special">!=</span> <span class="identifier">last</span><span class="special">)</span> <span class="comment">// fail if we did not get a full match</span> 180 <span class="keyword">return</span> <span class="keyword">false</span><span class="special">;</span> 181 <span class="keyword">return</span> <span class="identifier">r</span><span class="special">;</span> 182<span class="special">}</span> 183</pre> 184<p> 185 </p> 186<p> 187 The full cpp file for this example can be found here: <a href="../../../../../example/qi/sum.cpp" target="_top">../../example/qi/sum.cpp</a> 188 </p> 189<p> 190 This is almost like our original numbers list example. We're incrementally 191 building on top of our examples. This time though, like in the complex 192 number example, we'll be adding the smarts. There's an accumulator (<code class="computeroutput"><span class="keyword">double</span><span class="special">&</span> <span class="identifier">n</span></code>) that adds the numbers parsed. On a 193 successful parse, this number is the sum of all the parsed numbers. 194 </p> 195<p> 196 The first <code class="computeroutput"><span class="identifier">double_</span></code> parser 197 attaches this action: 198 </p> 199<pre class="programlisting"><span class="identifier">ref</span><span class="special">(</span><span class="identifier">n</span><span class="special">)</span> <span class="special">=</span> <span class="identifier">_1</span> 200</pre> 201<p> 202 This assigns the parsed result (actually, the attribute of <code class="computeroutput"><span class="identifier">double_</span></code>) to <code class="computeroutput"><span class="identifier">n</span></code>. 203 <code class="computeroutput"><span class="identifier">ref</span><span class="special">(</span><span class="identifier">n</span><span class="special">)</span></code> tells 204 <a href="../../../../../../../libs/phoenix/doc/html/index.html" target="_top">Boost.Phoenix</a> 205 that <code class="computeroutput"><span class="identifier">n</span></code> is a mutable reference. 206 <code class="computeroutput"><span class="identifier">_1</span></code> is a <a href="../../../../../../../libs/phoenix/doc/html/index.html" target="_top">Boost.Phoenix</a> 207 placeholder for the parsed result attribute. 208 </p> 209<p> 210 The second <code class="computeroutput"><span class="identifier">double_</span></code> parser 211 attaches this action: 212 </p> 213<pre class="programlisting"><span class="identifier">ref</span><span class="special">(</span><span class="identifier">n</span><span class="special">)</span> <span class="special">+=</span> <span class="identifier">_1</span> 214</pre> 215<p> 216 So, subsequent numbers add into <code class="computeroutput"><span class="identifier">n</span></code>. 217 </p> 218<p> 219 That wasn't too bad, was it :-) ? 220 </p> 221</div> 222<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 223<td align="left"></td> 224<td align="right"><div class="copyright-footer">Copyright © 2001-2011 Joel de Guzman, Hartmut Kaiser<p> 225 Distributed under the Boost Software License, Version 1.0. (See accompanying 226 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>) 227 </p> 228</div></td> 229</tr></table> 230<hr> 231<div class="spirit-nav"> 232<a accesskey="p" href="complex___our_first_complex_parser.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="number_list___stuffing_numbers_into_a_std__vector.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 233</div> 234</body> 235</html> 236
