Google Git
Sign in
nest-open-source / nest-learning-thermostat / 5.0 / boost / 317601cb979f96545d0e892ce7cfdf59f676ee0a / . / boost_1_45_0 / libs / spirit / doc / html / spirit / lex / tutorials / lexer_quickstart2.html
blob: c0ff360efaa07a062b66756e6d88a6d2fe34a05e [file] [log] [blame]
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<title>Quickstart 2 - A better word counter using Spirit.Lex</title>
<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
<meta name="generator" content="DocBook XSL Stylesheets V1.75.0">
<link rel="home" href="../../../index.html" title="Spirit 2.4.1">
<link rel="up" href="../tutorials.html" title="Spirit.Lex Tutorials">
<link rel="prev" href="lexer_quickstart1.html" title="Quickstart 1 - A word counter using Spirit.Lex">
<link rel="next" href="lexer_quickstart3.html" title="Quickstart 3 - Counting Words Using a Parser">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
<table cellpadding="2" width="100%"><tr>
<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td>
<td align="center"><a href="../../../../../../../index.html">Home</a></td>
<td align="center"><a href="../../../../../../../libs/libraries.htm">Libraries</a></td>
<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
<td align="center"><a href="../../../../../../../more/index.htm">More</a></td>
</tr></table>
<hr>
<div class="spirit-nav">
<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>
</div>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<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
2 - A better word counter using <span class="emphasis"><em>Spirit.Lex</em></span></a>
</h4></div></div></div>
<p>
People familiar with <a href="http://flex.sourceforge.net/" target="_top">Flex</a>
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
Quickstart 1 - A word counter using <span class="emphasis"><em>Spirit.Lex</em></span></a>
as being overly complex and not being written to leverage the possibilities
provided by this tool. In particular the previous example did not directly
use the lexer actions to count the lines, words, and characters. So the
example provided in this step of the tutorial will show how to use semantic
actions in <span class="emphasis"><em>Spirit.Lex</em></span>. Even though this examples still
counts textual elements, the purpose is to introduce new concepts and configuration
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>).
</p>
<a name="spirit.lex.tutorials.lexer_quickstart2.prerequisites"></a><h6>
<a name="id1120913"></a>
<a class="link" href="lexer_quickstart2.html#spirit.lex.tutorials.lexer_quickstart2.prerequisites">Prerequisites</a>
</h6>
<p>
In addition to the only required <code class="computeroutput"><span class="preprocessor">#include</span></code>
specific to <span class="emphasis"><em>Spirit.Lex</em></span> this example needs to include
a couple of header files from the <a href="../../../../../phoenix/doc/html/index.html" target="_top">Boost.Phoenix</a>
library. This example shows how to attach functors to token definitions,
which could be done using any type of C++ technique resulting in a callable
object. Using <a href="../../../../../phoenix/doc/html/index.html" target="_top">Boost.Phoenix</a>
for this task simplifies things and avoids adding dependencies to other
libraries (<a href="../../../../../phoenix/doc/html/index.html" target="_top">Boost.Phoenix</a>
is already in use for <a href="http://boost-spirit.com" target="_top">Spirit</a>
anyway).
</p>
<p>
</p>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</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">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</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">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</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">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</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">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</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">&gt;</span>
</pre>
<p>
</p>
<p>
To make all the code below more readable we introduce the following namespaces.
</p>
<p>
</p>
<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>
</pre>
<p>
</p>
<p>
To give a preview at what to expect from this example, here is the flex
program which has been used as the starting point. The useful code is directly
included inside the actions associated with each of the token definitions.
</p>
<p>
</p>
<pre class="programlisting"><span class="special">%{</span>
<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>
<span class="special">%}</span>
<span class="special">%%</span>
<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>
<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>
<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>
<span class="special">%%</span>
<span class="identifier">main</span><span class="special">()</span>
<span class="special">{</span>
<span class="identifier">yylex</span><span class="special">();</span>
<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>
<span class="special">}</span>
</pre>
<p>
</p>
<a name="spirit.lex.tutorials.lexer_quickstart2.semantic_actions_in__emphasis_spirit_lex__emphasis_"></a><h6>
<a name="id1121531"></a>
<a class="link" href="lexer_quickstart2.html#spirit.lex.tutorials.lexer_quickstart2.semantic_actions_in__emphasis_spirit_lex__emphasis_">Semantic
Actions in <span class="emphasis"><em>Spirit.Lex</em></span></a>
</h6>
<p>
<span class="emphasis"><em>Spirit.Lex</em></span> uses a very similar way of associating
actions with the token definitions (which should look familiar to anybody
knowledgeable with <a href="http://boost-spirit.com" target="_top">Spirit</a>
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
semantic actions to token definitions for each of them there is defined
an instance of a <code class="computeroutput"><span class="identifier">token_def</span><span class="special">&lt;&gt;</span></code>.
</p>
<p>
</p>
<pre class="programlisting"><span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Lexer</span><span class="special">&gt;</span>
<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">&lt;</span><span class="identifier">Lexer</span><span class="special">&gt;</span>
<span class="special">{</span>
<span class="identifier">word_count_tokens</span><span class="special">()</span>
<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>
<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> <span class="special">,</span> <span class="identifier">eol</span><span class="special">(</span><span class="string">"\n"</span><span class="special">)</span>
<span class="special">,</span> <span class="identifier">any</span><span class="special">(</span><span class="string">"."</span><span class="special">)</span>
<span class="special">{</span>
<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>
<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>
<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>
<span class="comment">// associate tokens with the lexer
</span> <span class="keyword">this</span><span class="special">-&gt;</span><span class="identifier">self</span>
<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>
<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>
<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>
<span class="special">;</span>
<span class="special">}</span>
<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>
<span class="identifier">lex</span><span class="special">::</span><span class="identifier">token_def</span><span class="special">&lt;&gt;</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>
<span class="special">};</span>
</pre>
<p>
</p>
<p>
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
corresponding token has been matched by the lexical analyzer. This is very
similar to <a href="http://flex.sourceforge.net/" target="_top">Flex</a>, where
the action code associated with a token definition gets executed after
the recognition of a matching input sequence. The code above uses function
objects constructed using <a href="../../../../../phoenix/doc/html/index.html" target="_top">Boost.Phoenix</a>,
but it is possible to insert any C++ function or function object as long
as it exposes the proper interface. For more details on please refer to
the section <a class="link" href="../abstracts/lexer_semantic_actions.html" title="Lexer Semantic Actions">Lexer
Semantic Actions</a>.
</p>
<a name="spirit.lex.tutorials.lexer_quickstart2.associating_token_definitions_with_the_lexer"></a><h6>
<a name="id1122159"></a>
<a class="link" href="lexer_quickstart2.html#spirit.lex.tutorials.lexer_quickstart2.associating_token_definitions_with_the_lexer">Associating
Token Definitions with the Lexer</a>
</h6>
<p>
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
Quickstart 1 - A word counter using <span class="emphasis"><em>Spirit.Lex</em></span></a>
with regard to the way how token definitions are associated with the lexer,
you will notice a different syntax being used here. In the previous example
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
assign the token definitions to <code class="computeroutput"><span class="identifier">self</span></code>,
combining the different token definitions using the <code class="computeroutput"><span class="special">|</span></code>
operator. Here is the code snippet again:
</p>
<pre class="programlisting"><span class="keyword">this</span><span class="special">-&gt;</span><span class="identifier">self</span>
<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>
<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>
<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>
<span class="special">;</span>
</pre>
<p>
This way we have a very powerful and natural way of building the lexical
analyzer. If translated into English this may be read as: The lexical analyzer
will recognize ('<code class="computeroutput"><span class="special">=</span></code>') tokens
as defined by any of ('<code class="computeroutput"><span class="special">|</span></code>')
the token definitions <code class="computeroutput"><span class="identifier">word</span></code>,
<code class="computeroutput"><span class="identifier">eol</span></code>, and <code class="computeroutput"><span class="identifier">any</span></code>.
</p>
<p>
A second difference to the previous example is that we do not explicitly
specify any token ids to use for the separate tokens. Using semantic actions
to trigger some useful work has freed us from the need to define those.
To ensure every token gets assigned a id the <span class="emphasis"><em>Spirit.Lex</em></span>
library internally assigns unique numbers to the token definitions, starting
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>.
</p>
<a name="spirit.lex.tutorials.lexer_quickstart2.pulling_everything_together"></a><h6>
<a name="id1123008"></a>
<a class="link" href="lexer_quickstart2.html#spirit.lex.tutorials.lexer_quickstart2.pulling_everything_together">Pulling
everything together</a>
</h6>
<p>
In order to execute the code defined above we still need to instantiate
an instance of the lexer type, feed it from some input sequence and create
a pair of iterators allowing to iterate over the token sequence as created
by the lexer. This code shows how to achieve these steps:
</p>
<p>
</p>
<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>
<span class="special">{</span>
<a class="co" name="spirit4co" href="lexer_quickstart2.html#spirit4"><img src="../../../../../../../doc/src/images/callouts/1.png" alt="1" 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">token</span><span class="special">&lt;</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">&gt;</span>
<span class="identifier">token_type</span><span class="special">;</span>
<a class="co" name="spirit5co" href="lexer_quickstart2.html#spirit5"><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">&lt;</span><span class="identifier">token_type</span><span class="special">&gt;</span> <span class="identifier">lexer_type</span><span class="special">;</span>
<a class="co" name="spirit6co" href="lexer_quickstart2.html#spirit6"><img src="../../../../../../../doc/src/images/callouts/3.png" alt="3" border="0"></a> <span class="identifier">word_count_tokens</span><span class="special">&lt;</span><span class="identifier">lexer_type</span><span class="special">&gt;</span> <span class="identifier">word_count_lexer</span><span class="special">;</span>
<a class="co" name="spirit7co" href="lexer_quickstart2.html#spirit7"><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>
<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>
<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">&amp;</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>
<a class="co" name="spirit8co" href="lexer_quickstart2.html#spirit8"><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>
<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>
<a class="co" name="spirit9co" href="lexer_quickstart2.html#spirit9"><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">&amp;&amp;</span> <span class="identifier">token_is_valid</span><span class="special">(*</span><span class="identifier">iter</span><span class="special">))</span>
<span class="special">++</span><span class="identifier">iter</span><span class="special">;</span>
<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>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"lines: "</span> <span class="special">&lt;&lt;</span> <span class="identifier">word_count_lexer</span><span class="special">.</span><span class="identifier">l</span>
<span class="special">&lt;&lt;</span> <span class="string">", words: "</span> <span class="special">&lt;&lt;</span> <span class="identifier">word_count_lexer</span><span class="special">.</span><span class="identifier">w</span>
<span class="special">&lt;&lt;</span> <span class="string">", characters: "</span> <span class="special">&lt;&lt;</span> <span class="identifier">word_count_lexer</span><span class="special">.</span><span class="identifier">c</span>
<span class="special">&lt;&lt;</span> <span class="string">"\n"</span><span class="special">;</span>
<span class="special">}</span>
<span class="keyword">else</span> <span class="special">{</span>
<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>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"Lexical analysis failed\n"</span> <span class="special">&lt;&lt;</span> <span class="string">"stopped at: \""</span>
<span class="special">&lt;&lt;</span> <span class="identifier">rest</span> <span class="special">&lt;&lt;</span> <span class="string">"\"\n"</span><span class="special">;</span>
<span class="special">}</span>
<span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
</p>
<div class="calloutlist"><table border="0" summary="Callout list">
<tr>
<td width="5%" valign="top" align="left"><p><a name="spirit4"></a><a href="#spirit4co"><img src="../../../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a> </p></td>
<td valign="top" align="left"><p>
Specifying <code class="computeroutput"><span class="identifier">omit</span></code> as
the token attribute type generates a token class not holding any token
attribute at all (not even the iterator range of the matched input
sequence), therefore optimizing the token, the lexer, and possibly
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
generates a token type and an iterator, both holding no lexer state,
allowing for even more aggressive optimizations. As a result the token
instances contain the token ids as the only data member.
</p></td>
</tr>
<tr>
<td width="5%" valign="top" align="left"><p><a name="spirit5"></a><a href="#spirit5co"><img src="../../../../../../../doc/src/images/callouts/2.png" alt="2" border="0"></a> </p></td>
<td valign="top" align="left"><p>
This defines the lexer type to use
</p></td>
</tr>
<tr>
<td width="5%" valign="top" align="left"><p><a name="spirit6"></a><a href="#spirit6co"><img src="../../../../../../../doc/src/images/callouts/3.png" alt="3" border="0"></a> </p></td>
<td valign="top" align="left"><p>
Create the lexer object instance needed to invoke the lexical analysis
</p></td>
</tr>
<tr>
<td width="5%" valign="top" align="left"><p><a name="spirit7"></a><a href="#spirit7co"><img src="../../../../../../../doc/src/images/callouts/4.png" alt="4" border="0"></a> </p></td>
<td valign="top" align="left"><p>
Read input from the given file, tokenize all the input, while discarding
all generated tokens
</p></td>
</tr>
<tr>
<td width="5%" valign="top" align="left"><p><a name="spirit8"></a><a href="#spirit8co"><img src="../../../../../../../doc/src/images/callouts/5.png" alt="5" border="0"></a> </p></td>
<td valign="top" align="left"><p>
Create a pair of iterators returning the sequence of generated tokens
</p></td>
</tr>
<tr>
<td width="5%" valign="top" align="left"><p><a name="spirit9"></a><a href="#spirit9co"><img src="../../../../../../../doc/src/images/callouts/6.png" alt="6" border="0"></a> </p></td>
<td valign="top" align="left"><p>
Here we simply iterate over all tokens, making sure to break the loop
if an invalid token gets returned from the lexer
</p></td>
</tr>
</table></div>
</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 &#169; 2001-2010 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>
<hr>
<div class="spirit-nav">
<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>
</div>
</body>
</html>