<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> <title>Lexer</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"> <link rel="up" href="../lexer_concepts.html" title="Lexer Concepts"> <link rel="prev" href="../lexer_concepts.html" title="Lexer Concepts"> <link rel="next" href="primitivelexer.html" title="PrimitiveLexer"> </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_concepts.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../lexer_concepts.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="primitivelexer.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> </div> <div class="section"> <div class="titlepage"><div><div><h5 class="title"> <a name="spirit.lex.reference.lexer_concepts.lexer"></a><a class="link" href="lexer.html" title="Lexer">Lexer</a> </h5></div></div></div> <a name="spirit.lex.reference.lexer_concepts.lexer.description"></a><h6> <a name="id1187053"></a> <a class="link" href="lexer.html#spirit.lex.reference.lexer_concepts.lexer.description">Description</a> </h6> <p> The <span class="emphasis"><em>Lexer</em></span> is the most fundamental concept. A Lexer has a member function, <code class="computeroutput"><span class="identifier">collect</span></code>, that accepts a token definition container <code class="computeroutput"><span class="identifier">Def</span></code>, and a the name of the lexer state the token definitions of the lexer component need to be added to (a string). It doesn't return anything (return type is <code class="computeroutput"><span class="keyword">void</span></code>). Each Lexer can represent a specific pattern or algorithm, or it can be a more complex lexer component formed as a composition of other Lexer's. Additionally, a Lexer exposes a member <code class="computeroutput"><span class="identifier">add_actions</span></code>, that accepts the token definition container <code class="computeroutput"><span class="identifier">Def</span></code>, while returning nothing (again, the returned type is <code class="computeroutput"><span class="keyword">void</span></code>). </p> <div class="variablelist"> <p class="title"><b>Notation</b></p> <dl> <dt><span class="term"><code class="computeroutput"><span class="identifier">l</span></code></span></dt> <dd><p> A <code class="computeroutput"><span class="identifier">Lexer</span></code>. </p></dd> <dt><span class="term"><code class="computeroutput"><span class="identifier">L</span></code></span></dt> <dd><p> A <code class="computeroutput"><span class="identifier">Lexer</span></code> type. </p></dd> <dt><span class="term"><code class="computeroutput"><span class="identifier">Def</span></code></span></dt> <dd><p> A token definition conatiner type. </p></dd> <dt><span class="term"><code class="computeroutput"><span class="identifier">State</span></code></span></dt> <dd><p> A type used to represent lexer state names. </p></dd> </dl> </div> <a name="spirit.lex.reference.lexer_concepts.lexer.valid_expressions"></a><h6> <a name="id1187219"></a> <a class="link" href="lexer.html#spirit.lex.reference.lexer_concepts.lexer.valid_expressions">Valid Expressions</a> </h6> <p> In the expressions below, the behavior of the lexer component, <code class="computeroutput"><span class="identifier">l</span></code>, is left unspecified in the base <code class="computeroutput"><span class="identifier">Lexer</span></code> concept. These are specified in subsequent, more refined concepts and by the actual models thereof. </p> <p> For any Lexer the following expressions must be valid: </p> <div class="informaltable"><table class="table"> <colgroup> <col> <col> <col> </colgroup> <thead><tr> <th> <p> Expression </p> </th> <th> <p> Semantics </p> </th> <th> <p> Return type </p> </th> </tr></thead> <tbody> <tr> <td> <p> <code class="computeroutput"><span class="identifier">l</span><span class="special">.</span><span class="identifier">collect</span><span class="special">(</span><span class="identifier">def</span><span class="special">,</span> <span class="identifier">state</span><span class="special">)</span></code> </p> </td> <td> <p> Add all token definitions provided by this Lexer instance to the lexer state <code class="computeroutput"><span class="identifier">state</span></code> of the token definition container <code class="computeroutput"><span class="identifier">def</span></code>. </p> </td> <td> <p> <code class="computeroutput"><span class="keyword">void</span></code> </p> </td> </tr> <tr> <td> <p> <code class="computeroutput"><span class="identifier">l</span><span class="special">.</span><span class="identifier">add_actions</span><span class="special">(</span><span class="identifier">def</span><span class="special">)</span></code> </p> </td> <td> <p> Add all semantic actions provided by this Lexer instance to the token definition container <code class="computeroutput"><span class="identifier">def</span></code>. </p> </td> <td> <p> <code class="computeroutput"><span class="keyword">void</span></code> </p> </td> </tr> </tbody> </table></div> <a name="spirit.lex.reference.lexer_concepts.lexer.type_expressions"></a><h6> <a name="id1187447"></a> <a class="link" href="lexer.html#spirit.lex.reference.lexer_concepts.lexer.type_expressions">Type Expressions</a> </h6> <div class="informaltable"><table class="table"> <colgroup> <col> <col> </colgroup> <thead><tr> <th> <p> Expression </p> </th> <th> <p> Description </p> </th> </tr></thead> <tbody><tr> <td> <p> <code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">is_lexer</span><span class="special"><</span><span class="identifier">L</span><span class="special">>::</span><span class="identifier">type</span></code> </p> </td> <td> <p> Metafunction that evaluates to <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">true_</span></code> if a certain type, <code class="computeroutput"><span class="identifier">L</span></code> is a Lexer, <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">false_</span></code> otherwise (See <a href="../../../../../../../../libs/mpl/doc/refmanual/integral-constant.html" target="_top">MPL Boolean Constant</a>). </p> </td> </tr></tbody> </table></div> <a name="spirit.lex.reference.lexer_concepts.lexer.postcondition"></a><h6> <a name="id1187587"></a> <a class="link" href="lexer.html#spirit.lex.reference.lexer_concepts.lexer.postcondition">Postcondition</a> </h6> <p> Upon return from <code class="computeroutput"><span class="identifier">l</span><span class="special">.</span><span class="identifier">collect</span></code> the following post conditions should hold: </p> <div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"> On return, <code class="computeroutput"><span class="identifier">def</span></code> holds all token definitions defined in the Lexer, <code class="computeroutput"><span class="identifier">l</span></code>. This includes all Lexer's contained inside <code class="computeroutput"><span class="identifier">l</span></code>. </li></ul></div> <p> Upon return from <code class="computeroutput"><span class="identifier">l</span><span class="special">.</span><span class="identifier">add_actions</span></code> the following post conditions should hold: </p> <div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"> On return, <code class="computeroutput"><span class="identifier">def</span></code> holds all semantic actions correctly asociated with the corresponding token definitions as defined in the Lexer, <code class="computeroutput"><span class="identifier">l</span></code>. This includes all semantic actiosn defined by the Lexer's contained inside <code class="computeroutput"><span class="identifier">l</span></code>. </li></ul></div> <a name="spirit.lex.reference.lexer_concepts.lexer.models"></a><h6> <a name="id1187702"></a> <a class="link" href="lexer.html#spirit.lex.reference.lexer_concepts.lexer.models">Models</a> </h6> <p> All lexer components in <span class="emphasis"><em>Spirit.Lex</em></span> are models of the <span class="emphasis"><em>Lexer</em></span> concept. </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 © 2001-2010 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_concepts.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../lexer_concepts.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="primitivelexer.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> </div> </body> </html>