<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> <title>Qi Confix Parser Directive</title> <link rel="stylesheet" href="../../../../../../../../doc/src/boostbook.css" type="text/css"> <meta name="generator" content="DocBook XSL Stylesheets V1.75.2"> <link rel="home" href="../../../index.html" title="Spirit Repository 0.1"> <link rel="up" href="../directives.html" title="Qi Parser Directives"> <link rel="prev" href="../directives.html" title="Qi Parser Directives"> <link rel="next" href="distinct.html" title="Qi Distinct Parser Directive"> </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="../directives.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../directives.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="distinct.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_repository.qi_components.directives.confix"></a><a class="link" href="confix.html" title="Qi Confix Parser Directive"> Qi Confix Parser Directive</a> </h4></div></div></div> <a name="spirit_repository.qi_components.directives.confix.description"></a><h6> <a name="id761680"></a> <a class="link" href="confix.html#spirit_repository.qi_components.directives.confix.description">Description</a> </h6> <p> The <span class="emphasis"><em>Spirit.Qi</em></span> <code class="computeroutput"><span class="identifier">confix</span></code> directive is a unary parser component allowing to embed a parser (the subject) inside an opening (the prefix) and a closing (the suffix): </p> <pre class="programlisting"><span class="identifier">confix</span><span class="special">(</span><span class="identifier">prefix</span><span class="special">,</span> <span class="identifier">suffix</span><span class="special">)[</span><span class="identifier">subject</span><span class="special">]</span> </pre> <p> This results in a parser that is equivalent to the sequence </p> <pre class="programlisting"><span class="identifier">omit</span><span class="special">[</span><span class="identifier">prefix</span><span class="special">]</span> <span class="special">>></span> <span class="identifier">subject</span> <span class="special">>></span> <span class="identifier">omit</span><span class="special">[</span><span class="identifier">suffix</span><span class="special">]</span> </pre> <p> A simple example is a parser for non-nested comments which can now be written as: </p> <pre class="programlisting"><span class="identifier">confix</span><span class="special">(</span><span class="string">"/*"</span><span class="special">,</span> <span class="string">"*/"</span><span class="special">)[*(</span><span class="identifier">char_</span> <span class="special">-</span> <span class="string">"*/"</span><span class="special">)]</span> <span class="comment">// C style comment </span><span class="identifier">confix</span><span class="special">(</span><span class="string">"//"</span><span class="special">,</span> <span class="identifier">eol</span><span class="special">)[*(</span><span class="identifier">char_</span> <span class="special">-</span> <span class="identifier">eol</span><span class="special">)]</span> <span class="comment">// C++ style comment </span></pre> <p> Using the <code class="computeroutput"><span class="identifier">confix</span></code> directive instead of the explicit sequence has the advantage of being able to encapsulate the prefix and the suffix into a separate construct. The following code snippet illustrates the idea: </p> <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">spirit</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="keyword">namespace</span> <span class="identifier">repo</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">repository</span><span class="special">;</span> <span class="comment">// Define a metafunction allowing to compute the type </span><span class="comment">// of the confix() construct </span><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Prefix</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Suffix</span> <span class="special">=</span> <span class="identifier">Prefix</span><span class="special">></span> <span class="keyword">struct</span> <span class="identifier">confix_spec</span> <span class="special">{</span> <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">spirit</span><span class="special">::</span><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">terminal</span><span class="special"><</span> <span class="identifier">repo</span><span class="special">::</span><span class="identifier">tag</span><span class="special">::</span><span class="identifier">confix</span><span class="special">(</span><span class="identifier">Prefix</span><span class="special">,</span> <span class="identifier">Suffix</span><span class="special">)</span> <span class="special">>::</span><span class="identifier">type</span> <span class="identifier">type</span><span class="special">;</span> <span class="special">};</span> <span class="identifier">confix_spec</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">>::</span><span class="identifier">type</span> <span class="keyword">const</span> <span class="identifier">c_comment</span> <span class="special">=</span> <span class="identifier">repo</span><span class="special">::</span><span class="identifier">confix</span><span class="special">(</span><span class="string">"/*"</span><span class="special">,</span> <span class="string">"*/"</span><span class="special">);</span> <span class="identifier">confix_spec</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">>::</span><span class="identifier">type</span> <span class="keyword">const</span> <span class="identifier">cpp_comment</span> <span class="special">=</span> <span class="identifier">repo</span><span class="special">::</span><span class="identifier">confix</span><span class="special">(</span><span class="string">"//"</span><span class="special">,</span> <span class="string">"\n"</span><span class="special">);</span> </pre> <p> Now, the comment parsers can be written as </p> <pre class="programlisting"><span class="identifier">c_comment</span><span class="special">[*(</span><span class="identifier">char_</span> <span class="special">-</span> <span class="string">"*/"</span><span class="special">)]</span> <span class="comment">// C style comment </span><span class="identifier">cpp_comment</span><span class="special">[*(</span><span class="identifier">char_</span> <span class="special">-</span> <span class="identifier">eol</span><span class="special">)]</span> <span class="comment">// C++ style comment </span></pre> <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> While the <code class="computeroutput"><span class="identifier">confix_p</span><span class="special">(</span><span class="identifier">prefix</span><span class="special">,</span> <span class="identifier">subject</span><span class="special">,</span> <span class="identifier">suffix</span><span class="special">)</span></code> parser in <span class="emphasis"><em>Spirit.Classic</em></span> was equivalent to the sequence <code class="computeroutput"><span class="identifier">prefix</span> <span class="special">>></span> <span class="special">*(</span><span class="identifier">subject</span> <span class="special">-</span> <span class="identifier">suffix</span><span class="special">)</span> <span class="special">>></span> <span class="identifier">suffix</span><span class="special">,</span> <span class="identifier">the</span> <span class="emphasis"><em>Spirit.Qi</em></span> </code>confix` directive will not perform this refactoring any more. This simplifies the code and makes things more explicit. </p></td></tr> </table></div> <a name="spirit_repository.qi_components.directives.confix.header"></a><h6> <a name="id762520"></a> <a class="link" href="confix.html#spirit_repository.qi_components.directives.confix.header">Header</a> </h6> <pre class="programlisting"><span class="comment">// forwards to <boost/spirit/repository/home/qi/directive/confix.hpp> </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">repository</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">qi_confix</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> </pre> <a name="spirit_repository.qi_components.directives.confix.synopsis"></a><h6> <a name="id762608"></a> <a class="link" href="confix.html#spirit_repository.qi_components.directives.confix.synopsis">Synopsis</a> </h6> <pre class="programlisting"><span class="identifier">confix</span><span class="special">(</span><span class="identifier">prefix</span><span class="special">,</span> <span class="identifier">suffix</span><span class="special">)[</span><span class="identifier">subject</span><span class="special">]</span> </pre> <a name="spirit_repository.qi_components.directives.confix.parameters"></a><h6> <a name="id762664"></a> <a class="link" href="confix.html#spirit_repository.qi_components.directives.confix.parameters">Parameters</a> </h6> <div class="informaltable"><table class="table"> <colgroup> <col> <col> </colgroup> <thead><tr> <th> <p> Parameter </p> </th> <th> <p> Description </p> </th> </tr></thead> <tbody> <tr> <td> <p> <code class="computeroutput"><span class="identifier">prefix</span></code> </p> </td> <td> <p> The parser for the opening (the prefix). </p> </td> </tr> <tr> <td> <p> <code class="computeroutput"><span class="identifier">suffix</span></code> </p> </td> <td> <p> The parser for the ending (the suffix). </p> </td> </tr> <tr> <td> <p> <code class="computeroutput"><span class="identifier">subject</span></code> </p> </td> <td> <p> The parser for the input sequence between the <code class="computeroutput"><span class="identifier">prefix</span></code> and <code class="computeroutput"><span class="identifier">suffix</span></code> parts. </p> </td> </tr> </tbody> </table></div> <p> All three parameters can be arbitrarily complex parsers themselves. </p> <a name="spirit_repository.qi_components.directives.confix.attribute"></a><h6> <a name="id762814"></a> <a class="link" href="confix.html#spirit_repository.qi_components.directives.confix.attribute">Attribute</a> </h6> <p> The <code class="computeroutput"><span class="identifier">confix</span></code> directive exposes the attribute type of its subject as its own attribute type. If the <code class="computeroutput"><span class="identifier">subject</span></code> does not expose any attribute (the type is <code class="computeroutput"><span class="identifier">unused_type</span></code>), then the <code class="computeroutput"><span class="identifier">confix</span></code> does not expose any attribute either. </p> <pre class="programlisting"><span class="identifier">a</span><span class="special">:</span> <span class="identifier">A</span><span class="special">,</span> <span class="identifier">p</span><span class="special">:</span> <span class="identifier">P</span><span class="special">,</span> <span class="identifier">s</span><span class="special">:</span> <span class="identifier">S</span><span class="special">:</span> <span class="special">--></span> <span class="identifier">confix</span><span class="special">(</span><span class="identifier">p</span><span class="special">,</span> <span class="identifier">s</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]:</span> <span class="identifier">A</span> </pre> <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> This notation is used all over the Spirit documentation and reads as: Given, <code class="computeroutput"><span class="identifier">a</span></code>, <code class="computeroutput"><span class="identifier">p</span></code>, and <code class="computeroutput"><span class="identifier">s</span></code> are parsers, and <code class="computeroutput"><span class="identifier">A</span></code>, <code class="computeroutput"><span class="identifier">P</span></code>, and <code class="computeroutput"><span class="identifier">S</span></code> are the types of their attributes, then the type of the attribute exposed by <code class="computeroutput"><span class="identifier">confix</span><span class="special">(</span><span class="identifier">p</span><span class="special">,</span> <span class="identifier">s</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span></code> will be <code class="computeroutput"><span class="identifier">A</span></code>. </p></td></tr> </table></div> <a name="spirit_repository.qi_components.directives.confix.example"></a><h6> <a name="id763077"></a> <a class="link" href="confix.html#spirit_repository.qi_components.directives.confix.example">Example</a> </h6> <p> The following example shows simple use cases of the <code class="computeroutput"><span class="identifier">confix</span></code> directive. We will illustrate its usage by generating parsers for different comment styles and for some simple tagged data (for the full example code see <a href="../../../../../example/qi/confix.cpp" target="_top">confix.cpp</a>) </p> <a name="spirit_repository.qi_components.directives.confix.prerequisites"></a><h6> <a name="id763116"></a> <a class="link" href="confix.html#spirit_repository.qi_components.directives.confix.prerequisites">Prerequisites</a> </h6> <p> In addition to the main header file needed to include the core components implemented in <span class="emphasis"><em>Spirit.Qi</em></span> we add the header file needed for the new <code class="computeroutput"><span class="identifier">confix</span></code> directive. </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">repository</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">qi_confix</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> </pre> <p> </p> <p> In order to make the examples below more readable we import a number of elements into the current namespace: </p> <p> </p> <pre class="programlisting"><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">eol</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">lexeme</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">ascii</span><span class="special">::</span><span class="identifier">alnum</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">ascii</span><span class="special">::</span><span class="identifier">char_</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">ascii</span><span class="special">::</span><span class="identifier">space</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">qi</span><span class="special">::</span><span class="identifier">parse</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">qi</span><span class="special">::</span><span class="identifier">phrase_parse</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">repository</span><span class="special">::</span><span class="identifier">confix</span><span class="special">;</span> </pre> <p> </p> <a name="spirit_repository.qi_components.directives.confix.parsing_different_comment_styles"></a><h6> <a name="id763572"></a> <a class="link" href="confix.html#spirit_repository.qi_components.directives.confix.parsing_different_comment_styles">Parsing Different Comment Styles</a> </h6> <p> We will show how to parse different comment styles. First we will parse a C++ comment: </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">parse_cpp_comment</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">string</span><span class="special">&</span> <span class="identifier">attr</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">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="identifier">confix</span><span class="special">(</span><span class="string">"//"</span><span class="special">,</span> <span class="identifier">eol</span><span class="special">)[*(</span><span class="identifier">char_</span> <span class="special">-</span> <span class="identifier">eol</span><span class="special">)],</span> <span class="comment">// grammar </span> <span class="identifier">attr</span><span class="special">);</span> <span class="comment">// attribute </span> <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> <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> This function will obviously parse input such as "<code class="computeroutput"><span class="comment">// This is a comment \n </span></code>". Similarily parsing a 'C'-style comment proves to be straightforward: </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">parse_c_comment</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">string</span><span class="special">&</span> <span class="identifier">attr</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">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="identifier">confix</span><span class="special">(</span><span class="string">"/*"</span><span class="special">,</span> <span class="string">"*/"</span><span class="special">)[*(</span><span class="identifier">char_</span> <span class="special">-</span> <span class="string">"*/"</span><span class="special">)],</span> <span class="comment">// grammar </span> <span class="identifier">attr</span><span class="special">);</span> <span class="comment">// attribute </span> <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> <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> which again will be able to parse e.g. "<code class="computeroutput"><span class="comment">/* This is a comment */</span> </code>". </p> <a name="spirit_repository.qi_components.directives.confix.parsing_tagged_data"></a><h6> <a name="id764198"></a> <a class="link" href="confix.html#spirit_repository.qi_components.directives.confix.parsing_tagged_data">Parsing Tagged Data</a> </h6> <p> Generating a parser that extracts the body from the HTML snippet "<code class="computeroutput"><span class="special"><</span><span class="identifier">b</span><span class="special">></span><span class="identifier">The</span> <span class="identifier">Body</span><span class="special"></</span><span class="identifier">b</span><span class="special">></span></code>" is not very hard, either: </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">parse_tagged</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">string</span><span class="special">&</span> <span class="identifier">attr</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">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="identifier">confix</span><span class="special">(</span><span class="string">"<b>"</span><span class="special">,</span> <span class="string">"</b>"</span><span class="special">)[</span><span class="identifier">lexeme</span><span class="special">[*(</span><span class="identifier">char_</span> <span class="special">-</span> <span class="char">'<'</span><span class="special">)]],</span> <span class="comment">// grammar </span> <span class="identifier">space</span><span class="special">,</span> <span class="comment">// skip </span> <span class="identifier">attr</span><span class="special">);</span> <span class="comment">// attribute </span> <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> <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> </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="../directives.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../directives.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="distinct.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> </div> </body> </html>