1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Quickstart 2 - A better word counter using Spirit.Lex</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="Spirit.Lex Tutorials"> 9<link rel="prev" href="lexer_quickstart1.html" title="Quickstart 1 - A word counter using Spirit.Lex"> 10<link rel="next" href="lexer_quickstart3.html" title="Quickstart 3 - Counting Words Using a Parser"> 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="lexer_quickstart1.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="lexer_quickstart3.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.lex.tutorials.lexer_quickstart2"></a><a class="link" href="lexer_quickstart2.html" title="Quickstart 2 - A better word counter using Spirit.Lex">Quickstart 28 2 - A better word counter using <span class="emphasis"><em>Spirit.Lex</em></span></a> 29</h4></div></div></div> 30<p> 31 People familiar with <a href="http://flex.sourceforge.net/" target="_top">Flex</a> 32 will probably complain about the example from the section <a class="link" href="lexer_quickstart1.html" title="Quickstart 1 - A word counter using Spirit.Lex">Lex 33 Quickstart 1 - A word counter using <span class="emphasis"><em>Spirit.Lex</em></span></a> 34 as being overly complex and not being written to leverage the possibilities 35 provided by this tool. In particular the previous example did not directly 36 use the lexer actions to count the lines, words, and characters. So the 37 example provided in this step of the tutorial will show how to use semantic 38 actions in <span class="emphasis"><em>Spirit.Lex</em></span>. Even though this examples still 39 counts textual elements, the purpose is to introduce new concepts and configuration 40 options along the lines (for the full example code see here: <a href="../../../../../example/lex/word_count_lexer.cpp" target="_top">word_count_lexer.cpp</a>). 41 </p> 42<h6> 43<a name="spirit.lex.tutorials.lexer_quickstart2.h0"></a> 44 <span class="phrase"><a name="spirit.lex.tutorials.lexer_quickstart2.prerequisites"></a></span><a class="link" href="lexer_quickstart2.html#spirit.lex.tutorials.lexer_quickstart2.prerequisites">Prerequisites</a> 45 </h6> 46<p> 47 In addition to the only required <code class="computeroutput"><span class="preprocessor">#include</span></code> 48 specific to <span class="emphasis"><em>Spirit.Lex</em></span> this example needs to include 49 a couple of header files from the <a href="../../../../../../../libs/phoenix/doc/html/index.html" target="_top">Boost.Phoenix</a> 50 library. This example shows how to attach functors to token definitions, 51 which could be done using any type of C++ technique resulting in a callable 52 object. Using <a href="../../../../../../../libs/phoenix/doc/html/index.html" target="_top">Boost.Phoenix</a> 53 for this task simplifies things and avoids adding dependencies to other 54 libraries (<a href="../../../../../../../libs/phoenix/doc/html/index.html" target="_top">Boost.Phoenix</a> 55 is already in use for <a href="http://boost-spirit.com" target="_top">Spirit</a> 56 anyway). 57 </p> 58<p> 59</p> 60<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">lex_lexertl</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 61<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> 62<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_statement</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 63<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_algorithm</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 64<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> 65</pre> 66<p> 67 </p> 68<p> 69 To make all the code below more readable we introduce the following namespaces. 70 </p> 71<p> 72</p> 73<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">lex</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">lex</span><span class="special">;</span> 74</pre> 75<p> 76 </p> 77<p> 78 To give a preview at what to expect from this example, here is the flex 79 program which has been used as the starting point. The useful code is directly 80 included inside the actions associated with each of the token definitions. 81 </p> 82<p> 83</p> 84<pre class="programlisting"><span class="special">%{</span> 85 <span class="keyword">int</span> <span class="identifier">c</span> <span class="special">=</span> <span class="number">0</span><span class="special">,</span> <span class="identifier">w</span> <span class="special">=</span> <span class="number">0</span><span class="special">,</span> <span class="identifier">l</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> 86<span class="special">%}</span> 87<span class="special">%%</span> 88<span class="special">[^</span> <span class="special">\</span><span class="identifier">t</span><span class="special">\</span><span class="identifier">n</span><span class="special">]+</span> <span class="special">{</span> <span class="special">++</span><span class="identifier">w</span><span class="special">;</span> <span class="identifier">c</span> <span class="special">+=</span> <span class="identifier">yyleng</span><span class="special">;</span> <span class="special">}</span> 89<span class="special">\</span><span class="identifier">n</span> <span class="special">{</span> <span class="special">++</span><span class="identifier">c</span><span class="special">;</span> <span class="special">++</span><span class="identifier">l</span><span class="special">;</span> <span class="special">}</span> 90<span class="special">.</span> <span class="special">{</span> <span class="special">++</span><span class="identifier">c</span><span class="special">;</span> <span class="special">}</span> 91<span class="special">%%</span> 92<span class="identifier">main</span><span class="special">()</span> 93<span class="special">{</span> 94 <span class="identifier">yylex</span><span class="special">();</span> 95 <span class="identifier">printf</span><span class="special">(</span><span class="string">"%d %d %d\n"</span><span class="special">,</span> <span class="identifier">l</span><span class="special">,</span> <span class="identifier">w</span><span class="special">,</span> <span class="identifier">c</span><span class="special">);</span> 96<span class="special">}</span> 97</pre> 98<p> 99 </p> 100<h6> 101<a name="spirit.lex.tutorials.lexer_quickstart2.h1"></a> 102 <span class="phrase"><a name="spirit.lex.tutorials.lexer_quickstart2.semantic_actions_in__emphasis_spirit_lex__emphasis_"></a></span><a class="link" href="lexer_quickstart2.html#spirit.lex.tutorials.lexer_quickstart2.semantic_actions_in__emphasis_spirit_lex__emphasis_">Semantic 103 Actions in <span class="emphasis"><em>Spirit.Lex</em></span></a> 104 </h6> 105<p> 106 <span class="emphasis"><em>Spirit.Lex</em></span> uses a very similar way of associating 107 actions with the token definitions (which should look familiar to anybody 108 knowledgeable with <a href="http://boost-spirit.com" target="_top">Spirit</a> 109 as well): specifying the operations to execute inside of a pair of <code class="computeroutput"><span class="special">[]</span></code> brackets. In order to be able to attach 110 semantic actions to token definitions for each of them there is defined 111 an instance of a <code class="computeroutput"><span class="identifier">token_def</span><span class="special"><></span></code>. 112 </p> 113<p> 114</p> 115<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Lexer</span><span class="special">></span> 116<span class="keyword">struct</span> <span class="identifier">word_count_tokens</span> <span class="special">:</span> <span class="identifier">lex</span><span class="special">::</span><span class="identifier">lexer</span><span class="special"><</span><span class="identifier">Lexer</span><span class="special">></span> 117<span class="special">{</span> 118 <span class="identifier">word_count_tokens</span><span class="special">()</span> 119 <span class="special">:</span> <span class="identifier">c</span><span class="special">(</span><span class="number">0</span><span class="special">),</span> <span class="identifier">w</span><span class="special">(</span><span class="number">0</span><span class="special">),</span> <span class="identifier">l</span><span class="special">(</span><span class="number">0</span><span class="special">)</span> 120 <span class="special">,</span> <span class="identifier">word</span><span class="special">(</span><span class="string">"[^ \t\n]+"</span><span class="special">)</span> <span class="comment">// define tokens</span> 121 <span class="special">,</span> <span class="identifier">eol</span><span class="special">(</span><span class="string">"\n"</span><span class="special">)</span> 122 <span class="special">,</span> <span class="identifier">any</span><span class="special">(</span><span class="string">"."</span><span class="special">)</span> 123 <span class="special">{</span> 124 <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">lex</span><span class="special">::</span><span class="identifier">_start</span><span class="special">;</span> 125 <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">lex</span><span class="special">::</span><span class="identifier">_end</span><span class="special">;</span> 126 <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> 127 128 <span class="comment">// associate tokens with the lexer</span> 129 <span class="keyword">this</span><span class="special">-></span><span class="identifier">self</span> 130 <span class="special">=</span> <span class="identifier">word</span> <span class="special">[++</span><span class="identifier">ref</span><span class="special">(</span><span class="identifier">w</span><span class="special">),</span> <span class="identifier">ref</span><span class="special">(</span><span class="identifier">c</span><span class="special">)</span> <span class="special">+=</span> <span class="identifier">distance</span><span class="special">(</span><span class="identifier">_start</span><span class="special">,</span> <span class="identifier">_end</span><span class="special">)]</span> 131 <span class="special">|</span> <span class="identifier">eol</span> <span class="special">[++</span><span class="identifier">ref</span><span class="special">(</span><span class="identifier">c</span><span class="special">),</span> <span class="special">++</span><span class="identifier">ref</span><span class="special">(</span><span class="identifier">l</span><span class="special">)]</span> 132 <span class="special">|</span> <span class="identifier">any</span> <span class="special">[++</span><span class="identifier">ref</span><span class="special">(</span><span class="identifier">c</span><span class="special">)]</span> 133 <span class="special">;</span> 134 <span class="special">}</span> 135 136 <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">c</span><span class="special">,</span> <span class="identifier">w</span><span class="special">,</span> <span class="identifier">l</span><span class="special">;</span> 137 <span class="identifier">lex</span><span class="special">::</span><span class="identifier">token_def</span><span class="special"><></span> <span class="identifier">word</span><span class="special">,</span> <span class="identifier">eol</span><span class="special">,</span> <span class="identifier">any</span><span class="special">;</span> 138<span class="special">};</span> 139</pre> 140<p> 141 </p> 142<p> 143 The semantics of the shown code is as follows. The code inside the <code class="computeroutput"><span class="special">[]</span></code> brackets will be executed whenever the 144 corresponding token has been matched by the lexical analyzer. This is very 145 similar to <a href="http://flex.sourceforge.net/" target="_top">Flex</a>, where 146 the action code associated with a token definition gets executed after 147 the recognition of a matching input sequence. The code above uses function 148 objects constructed using <a href="../../../../../../../libs/phoenix/doc/html/index.html" target="_top">Boost.Phoenix</a>, 149 but it is possible to insert any C++ function or function object as long 150 as it exposes the proper interface. For more details on please refer to 151 the section <a class="link" href="../abstracts/lexer_semantic_actions.html" title="Lexer Semantic Actions">Lexer 152 Semantic Actions</a>. 153 </p> 154<h6> 155<a name="spirit.lex.tutorials.lexer_quickstart2.h2"></a> 156 <span class="phrase"><a name="spirit.lex.tutorials.lexer_quickstart2.associating_token_definitions_with_the_lexer"></a></span><a class="link" href="lexer_quickstart2.html#spirit.lex.tutorials.lexer_quickstart2.associating_token_definitions_with_the_lexer">Associating 157 Token Definitions with the Lexer</a> 158 </h6> 159<p> 160 If you compare this code to the code from <a class="link" href="lexer_quickstart1.html" title="Quickstart 1 - A word counter using Spirit.Lex">Lex 161 Quickstart 1 - A word counter using <span class="emphasis"><em>Spirit.Lex</em></span></a> 162 with regard to the way how token definitions are associated with the lexer, 163 you will notice a different syntax being used here. In the previous example 164 we have been using the <code class="computeroutput"><span class="identifier">self</span><span class="special">.</span><span class="identifier">add</span><span class="special">()</span></code> style of the API, while we here directly 165 assign the token definitions to <code class="computeroutput"><span class="identifier">self</span></code>, 166 combining the different token definitions using the <code class="computeroutput"><span class="special">|</span></code> 167 operator. Here is the code snippet again: 168 </p> 169<pre class="programlisting"><span class="keyword">this</span><span class="special">-></span><span class="identifier">self</span> 170 <span class="special">=</span> <span class="identifier">word</span> <span class="special">[++</span><span class="identifier">ref</span><span class="special">(</span><span class="identifier">w</span><span class="special">),</span> <span class="identifier">ref</span><span class="special">(</span><span class="identifier">c</span><span class="special">)</span> <span class="special">+=</span> <span class="identifier">distance</span><span class="special">(</span><span class="identifier">_1</span><span class="special">)]</span> 171 <span class="special">|</span> <span class="identifier">eol</span> <span class="special">[++</span><span class="identifier">ref</span><span class="special">(</span><span class="identifier">c</span><span class="special">),</span> <span class="special">++</span><span class="identifier">ref</span><span class="special">(</span><span class="identifier">l</span><span class="special">)]</span> 172 <span class="special">|</span> <span class="identifier">any</span> <span class="special">[++</span><span class="identifier">ref</span><span class="special">(</span><span class="identifier">c</span><span class="special">)]</span> 173 <span class="special">;</span> 174</pre> 175<p> 176 This way we have a very powerful and natural way of building the lexical 177 analyzer. If translated into English this may be read as: The lexical analyzer 178 will recognize ('<code class="computeroutput"><span class="special">=</span></code>') tokens 179 as defined by any of ('<code class="computeroutput"><span class="special">|</span></code>') 180 the token definitions <code class="computeroutput"><span class="identifier">word</span></code>, 181 <code class="computeroutput"><span class="identifier">eol</span></code>, and <code class="computeroutput"><span class="identifier">any</span></code>. 182 </p> 183<p> 184 A second difference to the previous example is that we do not explicitly 185 specify any token ids to use for the separate tokens. Using semantic actions 186 to trigger some useful work has freed us from the need to define those. 187 To ensure every token gets assigned a id the <span class="emphasis"><em>Spirit.Lex</em></span> 188 library internally assigns unique numbers to the token definitions, starting 189 with the constant defined by <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">lex</span><span class="special">::</span><span class="identifier">min_token_id</span></code>. 190 </p> 191<h6> 192<a name="spirit.lex.tutorials.lexer_quickstart2.h3"></a> 193 <span class="phrase"><a name="spirit.lex.tutorials.lexer_quickstart2.pulling_everything_together"></a></span><a class="link" href="lexer_quickstart2.html#spirit.lex.tutorials.lexer_quickstart2.pulling_everything_together">Pulling 194 everything together</a> 195 </h6> 196<p> 197 In order to execute the code defined above we still need to instantiate 198 an instance of the lexer type, feed it from some input sequence and create 199 a pair of iterators allowing to iterate over the token sequence as created 200 by the lexer. This code shows how to achieve these steps: 201 </p> 202<p> 203</p> 204<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">main</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">argc</span><span class="special">,</span> <span class="keyword">char</span><span class="special">*</span> <span class="identifier">argv</span><span class="special">[])</span> 205<span class="special">{</span> 206 207<a class="co" name="spirit.lex.tutorials.lexer_quickstart2.c0" href="lexer_quickstart2.html#spirit.lex.tutorials.lexer_quickstart2.c1"><img src="../../../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a> <span class="keyword">typedef</span> 208 <span class="identifier">lex</span><span class="special">::</span><span class="identifier">lexertl</span><span class="special">::</span><span class="identifier">token</span><span class="special"><</span><span class="keyword">char</span> <span class="keyword">const</span><span class="special">*,</span> <span class="identifier">lex</span><span class="special">::</span><span class="identifier">omit</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">false_</span><span class="special">></span> 209 <span class="identifier">token_type</span><span class="special">;</span> 210 211<a class="co" name="spirit.lex.tutorials.lexer_quickstart2.c2" href="lexer_quickstart2.html#spirit.lex.tutorials.lexer_quickstart2.c3"><img src="../../../../../../../doc/src/images/callouts/2.png" alt="2" border="0"></a> <span class="keyword">typedef</span> <span class="identifier">lex</span><span class="special">::</span><span class="identifier">lexertl</span><span class="special">::</span><span class="identifier">actor_lexer</span><span class="special"><</span><span class="identifier">token_type</span><span class="special">></span> <span class="identifier">lexer_type</span><span class="special">;</span> 212 213<a class="co" name="spirit.lex.tutorials.lexer_quickstart2.c4" href="lexer_quickstart2.html#spirit.lex.tutorials.lexer_quickstart2.c5"><img src="../../../../../../../doc/src/images/callouts/3.png" alt="3" border="0"></a> <span class="identifier">word_count_tokens</span><span class="special"><</span><span class="identifier">lexer_type</span><span class="special">></span> <span class="identifier">word_count_lexer</span><span class="special">;</span> 214 215<a class="co" name="spirit.lex.tutorials.lexer_quickstart2.c6" href="lexer_quickstart2.html#spirit.lex.tutorials.lexer_quickstart2.c7"><img src="../../../../../../../doc/src/images/callouts/4.png" alt="4" border="0"></a> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">str</span> <span class="special">(</span><span class="identifier">read_from_file</span><span class="special">(</span><span class="number">1</span> <span class="special">==</span> <span class="identifier">argc</span> <span class="special">?</span> <span class="string">"word_count.input"</span> <span class="special">:</span> <span class="identifier">argv</span><span class="special">[</span><span class="number">1</span><span class="special">]));</span> 216 <span class="keyword">char</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">first</span> <span class="special">=</span> <span class="identifier">str</span><span class="special">.</span><span class="identifier">c_str</span><span class="special">();</span> 217 <span class="keyword">char</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">last</span> <span class="special">=</span> <span class="special">&</span><span class="identifier">first</span><span class="special">[</span><span class="identifier">str</span><span class="special">.</span><span class="identifier">size</span><span class="special">()];</span> 218 219<a class="co" name="spirit.lex.tutorials.lexer_quickstart2.c8" href="lexer_quickstart2.html#spirit.lex.tutorials.lexer_quickstart2.c9"><img src="../../../../../../../doc/src/images/callouts/5.png" alt="5" border="0"></a> <span class="identifier">lexer_type</span><span class="special">::</span><span class="identifier">iterator_type</span> <span class="identifier">iter</span> <span class="special">=</span> <span class="identifier">word_count_lexer</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(</span><span class="identifier">first</span><span class="special">,</span> <span class="identifier">last</span><span class="special">);</span> 220 <span class="identifier">lexer_type</span><span class="special">::</span><span class="identifier">iterator_type</span> <span class="identifier">end</span> <span class="special">=</span> <span class="identifier">word_count_lexer</span><span class="special">.</span><span class="identifier">end</span><span class="special">();</span> 221 222<a class="co" name="spirit.lex.tutorials.lexer_quickstart2.c10" href="lexer_quickstart2.html#spirit.lex.tutorials.lexer_quickstart2.c11"><img src="../../../../../../../doc/src/images/callouts/6.png" alt="6" border="0"></a> <span class="keyword">while</span> <span class="special">(</span><span class="identifier">iter</span> <span class="special">!=</span> <span class="identifier">end</span> <span class="special">&&</span> <span class="identifier">token_is_valid</span><span class="special">(*</span><span class="identifier">iter</span><span class="special">))</span> 223 <span class="special">++</span><span class="identifier">iter</span><span class="special">;</span> 224 225 <span class="keyword">if</span> <span class="special">(</span><span class="identifier">iter</span> <span class="special">==</span> <span class="identifier">end</span><span class="special">)</span> <span class="special">{</span> 226 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"lines: "</span> <span class="special"><<</span> <span class="identifier">word_count_lexer</span><span class="special">.</span><span class="identifier">l</span> 227 <span class="special"><<</span> <span class="string">", words: "</span> <span class="special"><<</span> <span class="identifier">word_count_lexer</span><span class="special">.</span><span class="identifier">w</span> 228 <span class="special"><<</span> <span class="string">", characters: "</span> <span class="special"><<</span> <span class="identifier">word_count_lexer</span><span class="special">.</span><span class="identifier">c</span> 229 <span class="special"><<</span> <span class="string">"\n"</span><span class="special">;</span> 230 <span class="special">}</span> 231 <span class="keyword">else</span> <span class="special">{</span> 232 <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">rest</span><span class="special">(</span><span class="identifier">first</span><span class="special">,</span> <span class="identifier">last</span><span class="special">);</span> 233 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Lexical analysis failed\n"</span> <span class="special"><<</span> <span class="string">"stopped at: \""</span> 234 <span class="special"><<</span> <span class="identifier">rest</span> <span class="special"><<</span> <span class="string">"\"\n"</span><span class="special">;</span> 235 <span class="special">}</span> 236 <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> 237<span class="special">}</span> 238</pre> 239<p> 240 </p> 241<div class="calloutlist"><table border="0" summary="Callout list"> 242<tr> 243<td width="5%" valign="top" align="left"><p><a name="spirit.lex.tutorials.lexer_quickstart2.c1"></a><a href="#spirit.lex.tutorials.lexer_quickstart2.c0"><img src="../../../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a> </p></td> 244<td valign="top" align="left"><p> 245 Specifying <code class="computeroutput"><span class="identifier">omit</span></code> as 246 the token attribute type generates a token class not holding any token 247 attribute at all (not even the iterator range of the matched input 248 sequence), therefore optimizing the token, the lexer, and possibly 249 the parser implementation as much as possible. Specifying <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">false_</span></code> as the 3rd template parameter 250 generates a token type and an iterator, both holding no lexer state, 251 allowing for even more aggressive optimizations. As a result the token 252 instances contain the token ids as the only data member. 253 </p></td> 254</tr> 255<tr> 256<td width="5%" valign="top" align="left"><p><a name="spirit.lex.tutorials.lexer_quickstart2.c3"></a><a href="#spirit.lex.tutorials.lexer_quickstart2.c2"><img src="../../../../../../../doc/src/images/callouts/2.png" alt="2" border="0"></a> </p></td> 257<td valign="top" align="left"><p> 258 This defines the lexer type to use 259 </p></td> 260</tr> 261<tr> 262<td width="5%" valign="top" align="left"><p><a name="spirit.lex.tutorials.lexer_quickstart2.c5"></a><a href="#spirit.lex.tutorials.lexer_quickstart2.c4"><img src="../../../../../../../doc/src/images/callouts/3.png" alt="3" border="0"></a> </p></td> 263<td valign="top" align="left"><p> 264 Create the lexer object instance needed to invoke the lexical analysis 265 </p></td> 266</tr> 267<tr> 268<td width="5%" valign="top" align="left"><p><a name="spirit.lex.tutorials.lexer_quickstart2.c7"></a><a href="#spirit.lex.tutorials.lexer_quickstart2.c6"><img src="../../../../../../../doc/src/images/callouts/4.png" alt="4" border="0"></a> </p></td> 269<td valign="top" align="left"><p> 270 Read input from the given file, tokenize all the input, while discarding 271 all generated tokens 272 </p></td> 273</tr> 274<tr> 275<td width="5%" valign="top" align="left"><p><a name="spirit.lex.tutorials.lexer_quickstart2.c9"></a><a href="#spirit.lex.tutorials.lexer_quickstart2.c8"><img src="../../../../../../../doc/src/images/callouts/5.png" alt="5" border="0"></a> </p></td> 276<td valign="top" align="left"><p> 277 Create a pair of iterators returning the sequence of generated tokens 278 </p></td> 279</tr> 280<tr> 281<td width="5%" valign="top" align="left"><p><a name="spirit.lex.tutorials.lexer_quickstart2.c11"></a><a href="#spirit.lex.tutorials.lexer_quickstart2.c10"><img src="../../../../../../../doc/src/images/callouts/6.png" alt="6" border="0"></a> </p></td> 282<td valign="top" align="left"><p> 283 Here we simply iterate over all tokens, making sure to break the loop 284 if an invalid token gets returned from the lexer 285 </p></td> 286</tr> 287</table></div> 288</div> 289<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 290<td align="left"></td> 291<td align="right"><div class="copyright-footer">Copyright © 2001-2011 Joel de Guzman, Hartmut Kaiser<p> 292 Distributed under the Boost Software License, Version 1.0. (See accompanying 293 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>) 294 </p> 295</div></td> 296</tr></table> 297<hr> 298<div class="spirit-nav"> 299<a accesskey="p" href="lexer_quickstart1.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="lexer_quickstart3.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 300</div> 301</body> 302</html> 303
