1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Complex - Our first complex parser</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="semantic_actions.html" title="Parser Semantic Actions"> 10<link rel="next" href="sum___adding_numbers.html" title="Sum - adding numbers"> 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="semantic_actions.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="sum___adding_numbers.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.complex___our_first_complex_parser"></a><a class="link" href="complex___our_first_complex_parser.html" title="Complex - Our first complex parser">Complex 28 - Our first complex parser</a> 29</h4></div></div></div> 30<p> 31 Well, not really a complex parser, but a parser that parses complex numbers. 32 This time, we're using <a href="../../../../../../../libs/phoenix/doc/html/index.html" target="_top">Boost.Phoenix</a> 33 to do the semantic actions. 34 </p> 35<p> 36 Here's a simple parser expression for complex numbers: 37 </p> 38<pre class="programlisting"> <span class="char">'('</span> <span class="special">>></span> <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> <span class="special">>></span> <span class="char">')'</span> 39<span class="special">|</span> <span class="identifier">double_</span> 40</pre> 41<p> 42 What's new? Well, we have: 43 </p> 44<div class="orderedlist"><ol class="orderedlist" type="1"> 45<li class="listitem"> 46 Alternates: e.g. <code class="computeroutput"><span class="identifier">a</span> <span class="special">|</span> <span class="identifier">b</span></code>. 47 Try <code class="computeroutput"><span class="identifier">a</span></code> first. If it 48 succeeds, good. If not, try the next alternative, <code class="computeroutput"><span class="identifier">b</span></code>. 49 </li> 50<li class="listitem"> 51 Optionals: e.g. -p. Match the parser p zero or one time. 52 </li> 53</ol></div> 54<p> 55 The complex parser presented above reads as: 56 </p> 57<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 58<li class="listitem"> 59 One or two real numbers in parentheses, separated by comma (the second 60 number is optional) 61 </li> 62<li class="listitem"> 63 <span class="bold"><strong>OR</strong></span> a single real number. 64 </li> 65</ul></div> 66<p> 67 This parser can parse complex numbers of the form: 68 </p> 69<pre class="programlisting"><span class="special">(</span><span class="number">123.45</span><span class="special">,</span> <span class="number">987.65</span><span class="special">)</span> 70<span class="special">(</span><span class="number">123.45</span><span class="special">)</span> 71<span class="number">123.45</span> 72</pre> 73<p> 74 Here goes, this time with actions: 75 </p> 76<p> 77</p> 78<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">client</span> 79<span class="special">{</span> 80 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Iterator</span><span class="special">></span> 81 <span class="keyword">bool</span> <span class="identifier">parse_complex</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="identifier">std</span><span class="special">::</span><span class="identifier">complex</span><span class="special"><</span><span class="keyword">double</span><span class="special">>&</span> <span class="identifier">c</span><span class="special">)</span> 82 <span class="special">{</span> 83 <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">qi</span><span class="special">::</span><span class="identifier">double_</span><span class="special">;</span> 84 <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">qi</span><span class="special">::</span><span class="identifier">_1</span><span class="special">;</span> 85 <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">qi</span><span class="special">::</span><span class="identifier">phrase_parse</span><span class="special">;</span> 86 <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> 87 <span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">phoenix</span><span class="special">::</span><span class="identifier">ref</span><span class="special">;</span> 88 89 <span class="keyword">double</span> <span class="identifier">rN</span> <span class="special">=</span> <span class="number">0.0</span><span class="special">;</span> 90 <span class="keyword">double</span> <span class="identifier">iN</span> <span class="special">=</span> <span class="number">0.0</span><span class="special">;</span> 91 <span class="keyword">bool</span> <span class="identifier">r</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> 92 93 <span class="comment">// Begin grammar</span> 94 <span class="special">(</span> 95 <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">rN</span><span class="special">)</span> <span class="special">=</span> <span class="identifier">_1</span><span class="special">]</span> 96 <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">iN</span><span class="special">)</span> <span class="special">=</span> <span class="identifier">_1</span><span class="special">])</span> <span class="special">>></span> <span class="char">')'</span> 97 <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">rN</span><span class="special">)</span> <span class="special">=</span> <span class="identifier">_1</span><span class="special">]</span> 98 <span class="special">),</span> 99 <span class="comment">// End grammar</span> 100 101 <span class="identifier">space</span><span class="special">);</span> 102 103 <span class="keyword">if</span> <span class="special">(!</span><span class="identifier">r</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> 104 <span class="keyword">return</span> <span class="keyword">false</span><span class="special">;</span> 105 <span class="identifier">c</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">complex</span><span class="special"><</span><span class="keyword">double</span><span class="special">>(</span><span class="identifier">rN</span><span class="special">,</span> <span class="identifier">iN</span><span class="special">);</span> 106 <span class="keyword">return</span> <span class="identifier">r</span><span class="special">;</span> 107 <span class="special">}</span> 108<span class="special">}</span> 109</pre> 110<p> 111 </p> 112<p> 113 The full cpp file for this example can be found here: <a href="../../../../../example/qi/complex_number.cpp" target="_top">../../example/qi/complex_number.cpp</a> 114 </p> 115<div class="note"><table border="0" summary="Note"> 116<tr> 117<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../images/note.png"></td> 118<th align="left">Note</th> 119</tr> 120<tr><td align="left" valign="top"><p> 121 Those with experience using <a href="../../../../../../../libs/phoenix/doc/html/index.html" target="_top">Boost.Phoenix</a> 122 might be confused with the placeholders that we are using (i.e. <code class="computeroutput"><span class="identifier">_1</span></code>, <code class="computeroutput"><span class="identifier">_2</span></code>, 123 etc.). Please be aware that we are not using the same placeholders supplied 124 by Phoenix. Take note that we are pulling in the placeholders from namespace 125 <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">qi</span></code>. These placeholders are specifically 126 tailored for Spirit. 127 </p></td></tr> 128</table></div> 129<p> 130 The <code class="computeroutput"><span class="identifier">double_</span></code> parser attaches 131 this action: 132 </p> 133<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> 134</pre> 135<p> 136 This assigns the parsed result (actually, the attribute of <code class="computeroutput"><span class="identifier">double_</span></code>) to n. <code class="computeroutput"><span class="identifier">ref</span><span class="special">(</span><span class="identifier">n</span><span class="special">)</span></code> 137 tells Phoenix that <code class="computeroutput"><span class="identifier">n</span></code> is 138 a mutable reference. <code class="computeroutput"><span class="identifier">_1</span></code> 139 is a Phoenix placeholder for the parsed result attribute. 140 </p> 141</div> 142<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 143<td align="left"></td> 144<td align="right"><div class="copyright-footer">Copyright © 2001-2011 Joel de Guzman, Hartmut Kaiser<p> 145 Distributed under the Boost Software License, Version 1.0. (See accompanying 146 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>) 147 </p> 148</div></td> 149</tr></table> 150<hr> 151<div class="spirit-nav"> 152<a accesskey="p" href="semantic_actions.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="sum___adding_numbers.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 153</div> 154</body> 155</html> 156
