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| <div class="section"> |
| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="spirit.qi.tutorials.sum___adding_numbers"></a><a class="link" href="sum___adding_numbers.html" title="Sum - adding numbers">Sum - adding |
| numbers</a> |
| </h4></div></div></div> |
| <p> |
| Here's a parser that sums a comma-separated list of numbers. |
| </p> |
| <p> |
| Ok we've glossed over some details in our previous examples. First, our |
| includes: |
| </p> |
| <p> |
| |
| </p> |
| <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> |
| <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> |
| <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> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">string</span><span class="special">></span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| Then some using directives: |
| </p> |
| <p> |
| |
| </p> |
| <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> |
| <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> |
| <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> |
| |
| <span class="keyword">using</span> <span class="identifier">qi</span><span class="special">::</span><span class="identifier">double_</span><span class="special">;</span> |
| <span class="keyword">using</span> <span class="identifier">qi</span><span class="special">::</span><span class="identifier">_1</span><span class="special">;</span> |
| <span class="keyword">using</span> <span class="identifier">ascii</span><span class="special">::</span><span class="identifier">space</span><span class="special">;</span> |
| <span class="keyword">using</span> <span class="identifier">phoenix</span><span class="special">::</span><span class="identifier">ref</span><span class="special">;</span> |
| </pre> |
| <p> |
| </p> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| <p> |
| Namespace |
| </p> |
| </th> |
| <th> |
| <p> |
| Description |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| boost::phoenix |
| </p> |
| </td> |
| <td> |
| <p> |
| All of phoenix |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| boost::spirit |
| </p> |
| </td> |
| <td> |
| <p> |
| All of spirit |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| boost::spirit::qi |
| </p> |
| </td> |
| <td> |
| <p> |
| All of spirit.qi |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| boost::spirit::ascii |
| </p> |
| </td> |
| <td> |
| <p> |
| ASCII version of <code class="computeroutput"><span class="identifier">char_</span></code> |
| and all char related parsers. Other encodings are also provided |
| (e.g. also an ISO8859.1) |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| boost::spirit::arg_names |
| </p> |
| </td> |
| <td> |
| <p> |
| Special phoenix placeholders for spirit |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| <div class="note"><table border="0" summary="Note"> |
| <tr> |
| <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../images/note.png"></td> |
| <th align="left">Note</th> |
| </tr> |
| <tr><td align="left" valign="top"><p> |
| If you feel uneasy with using whole namespaces, feel free to qualify |
| your code, use namespace aliases, etc. For the purpose of this tutorial, |
| we will be presenting unqualified names for both Spirit and <a href="../../../../../phoenix/doc/html/index.html" target="_top">Phoenix</a>. |
| No worries, we will always present the full working code, so you won't |
| get lost. In fact, all examples in this tutorial have a corresponding |
| cpp file that QuickBook (the documentation tool we are using) imports |
| in here as code snippets. |
| </p></td></tr> |
| </table></div> |
| <p> |
| Now the actual parser: |
| </p> |
| <p> |
| |
| </p> |
| <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> |
| <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> |
| <span class="special">{</span> |
| <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> |
| |
| <span class="comment">// Begin grammar |
| </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> <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> |
| <span class="special">)</span> |
| <span class="special">,</span> |
| <span class="comment">// End grammar |
| </span> |
| <span class="identifier">space</span><span class="special">);</span> |
| |
| <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> <span class="keyword">return</span> <span class="keyword">false</span><span class="special">;</span> |
| <span class="keyword">return</span> <span class="identifier">r</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| The full cpp file for this example can be found here: <a href="../../../../../example/qi/sum.cpp" target="_top">../../example/qi/sum.cpp</a> |
| </p> |
| <p> |
| This is almost like our original numbers list example. We're incrementally |
| building on top of our examples. This time though, like in the complex |
| 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 |
| successful parse, this number is the sum of all the parsed numbers. |
| </p> |
| <p> |
| The first <code class="computeroutput"><span class="identifier">double_</span></code> parser |
| attaches this action: |
| </p> |
| <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> |
| </pre> |
| <p> |
| 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>. |
| <code class="computeroutput"><span class="identifier">ref</span><span class="special">(</span><span class="identifier">n</span><span class="special">)</span></code> tells |
| <a href="../../../../../phoenix/doc/html/index.html" target="_top">Phoenix</a> that <code class="computeroutput"><span class="identifier">n</span></code> is a mutable reference. <code class="computeroutput"><span class="identifier">_1</span></code> is a <a href="../../../../../phoenix/doc/html/index.html" target="_top">Phoenix</a> |
| placeholder for the parsed result attribute. |
| </p> |
| <p> |
| The second <code class="computeroutput"><span class="identifier">double_</span></code> parser |
| attaches this action: |
| </p> |
| <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> |
| </pre> |
| <p> |
| So, subsequent numbers add into <code class="computeroutput"><span class="identifier">n</span></code>. |
| </p> |
| <p> |
| That wasn't too bad, was it :-) ? |
| </p> |
| </div> |
| <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> |
| <td align="left"></td> |
| <td align="right"><div class="copyright-footer">Copyright © 2001-2011 Joel de Guzman, Hartmut Kaiser<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| 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>) |
| </p> |
| </div></td> |
| </tr></table> |
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