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- <title>Qi Keyword Parser Directive</title>
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- </div>
- <div class="section">
- <div class="titlepage"><div><div><h4 class="title">
- <a name="spirit_repository.qi_components.directives.kwd"></a><a class="link" href="kwd.html" title="Qi Keyword Parser Directive">Qi
- Keyword Parser Directive </a>
- </h4></div></div></div>
- <h6>
- <a name="spirit_repository.qi_components.directives.kwd.h0"></a>
- <span class="phrase"><a name="spirit_repository.qi_components.directives.kwd.description"></a></span><a class="link" href="kwd.html#spirit_repository.qi_components.directives.kwd.description">Description</a>
- </h6>
- <p>
- The <code class="computeroutput"><span class="identifier">kwd</span><span class="special">[]</span></code>,
- <code class="computeroutput"><span class="identifier">dkwd</span><span class="special">[]</span></code>
- and <code class="computeroutput"><span class="identifier">ikwd</span><span class="special">[]</span></code>,
- <code class="computeroutput"><span class="identifier">idkwd</span><span class="special">[]</span></code>
- provide a powerful and flexible mechanism for parsing keyword based input.
- It works in conjuction with the / operator to create an effective keyword
- parsing loop. The keyword parsing loop doesn't require the keywords to
- appear in a defined order in the input but also provides the possibility
- to check how many times a keyword appears in the input.
- </p>
- <p>
- The kwd directive will parse the keywords respecting case sensitivity whereas
- the ikwd direcive is case insensitive. You can mix the kwd and ikwd directives
- inside a set of keywords, but be aware that this has a small overhead.
- It should be prefered not to mix the kwd and ikwd directives.
- </p>
- <p>
- The dkwd and idkwd provide a mechanism to pase distinct keywords. These
- directives require that the skipper successeds parsing input right after
- the keyword part.
- </p>
- <p>
- dkwd("keyword1")<span class="emphasis"><em>='>>int_</em></span>
- </p>
- <p>
- is equivalent to:
- </p>
- <p>
- lit("keyword1") >> skipper+ >> '=' >> int_
- </p>
- <p>
- All the keyword directives can be mixed inside a keyword list.
- </p>
- <p>
- The kwd directive is very similar to the repeat directive in that it enables
- to enforce keyword occurrence constraints but also provides very interesting
- speed improvement over the pure EBNF syntax or the Nabialek-Trick.
- </p>
- <h6>
- <a name="spirit_repository.qi_components.directives.kwd.h1"></a>
- <span class="phrase"><a name="spirit_repository.qi_components.directives.kwd.header"></a></span><a class="link" href="kwd.html#spirit_repository.qi_components.directives.kwd.header">Header</a>
- </h6>
- <pre class="programlisting"><span class="comment">// forwards to <boost/spirit/repository/home/qi/directive/kwd.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_kwd</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
- </pre>
- <h6>
- <a name="spirit_repository.qi_components.directives.kwd.h2"></a>
- <span class="phrase"><a name="spirit_repository.qi_components.directives.kwd.synopsis"></a></span><a class="link" href="kwd.html#spirit_repository.qi_components.directives.kwd.synopsis">Synopsis</a>
- </h6>
- <div class="informaltable"><table class="table">
- <colgroup>
- <col>
- <col>
- </colgroup>
- <thead><tr>
- <th>
- <p>
- Expression
- </p>
- </th>
- <th>
- <p>
- Semantics
- </p>
- </th>
- </tr></thead>
- <tbody>
- <tr>
- <td>
- <p>
- <code class="computeroutput"><span class="identifier">kwd</span><span class="special">(</span><span class="identifier">keyword</span><span class="special">)[</span><span class="identifier">subject</span><span class="special">]</span></code>
- </p>
- </td>
- <td>
- <p>
- Parse ( <code class="computeroutput"><span class="string">"keyword"</span></code>
- > <code class="computeroutput"><span class="identifier">subject</span></code>)
- zero or more times.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="computeroutput"><span class="identifier">kwd</span><span class="special">(</span><span class="identifier">keyword</span><span class="special">,</span><span class="identifier">n</span><span class="special">)[</span><span class="identifier">subject</span><span class="special">]</span></code>
- </p>
- </td>
- <td>
- <p>
- Parse ( <code class="computeroutput"><span class="string">"keyword"</span></code>
- > <code class="computeroutput"><span class="identifier">subject</span></code>)
- exactly <code class="computeroutput"><span class="identifier">n</span></code> times.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="computeroutput"><span class="identifier">kwd</span><span class="special">(</span><span class="identifier">keyword</span><span class="special">,</span><span class="identifier">min</span><span class="special">,</span>
- <span class="identifier">max</span><span class="special">)[</span><span class="identifier">subject</span><span class="special">]</span></code>
- </p>
- </td>
- <td>
- <p>
- Parse ( <code class="computeroutput"><span class="string">"keyword"</span></code>
- > <code class="computeroutput"><span class="identifier">subject</span></code>)
- at least <code class="computeroutput"><span class="identifier">min</span></code>
- times and at most <code class="computeroutput"><span class="identifier">max</span></code>
- times.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="computeroutput"><span class="identifier">kwd</span><span class="special">(</span><span class="identifier">keyword</span><span class="special">,</span><span class="identifier">min</span><span class="special">,</span>
- <span class="identifier">inf</span><span class="special">)[</span><span class="identifier">subject</span><span class="special">]</span></code>
- </p>
- </td>
- <td>
- <p>
- Parse ( <code class="computeroutput"><span class="string">"keyword"</span></code>
- > <code class="computeroutput"><span class="identifier">subject</span></code>)
- at least <code class="computeroutput"><span class="identifier">min</span></code>
- or more.
- </p>
- </td>
- </tr>
- </tbody>
- </table></div>
- <p>
- For non case sensitive keywords use the ikwd directive. If distinct keyword
- parsing is required, use the dkwd and idkwd directive instead.
- </p>
- <h6>
- <a name="spirit_repository.qi_components.directives.kwd.h3"></a>
- <span class="phrase"><a name="spirit_repository.qi_components.directives.kwd.parameters"></a></span><a class="link" href="kwd.html#spirit_repository.qi_components.directives.kwd.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">keyword</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">subject</span></code>
- </p>
- </td>
- <td>
- <p>
- The parser for the input sequence following the keyword part.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="computeroutput"><span class="identifier">n</span></code>
- </p>
- </td>
- <td>
- <p>
- Int representing the exact number of times the keyword must be
- repeated.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="computeroutput"><span class="identifier">min</span></code>
- </p>
- </td>
- <td>
- <p>
- Int representing the minimum number of times the keyword must
- be repeated.
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="computeroutput"><span class="identifier">max</span></code>
- </p>
- </td>
- <td>
- <p>
- Int representing the maximum number of times the keyword must
- be repeated.
- </p>
- </td>
- </tr>
- </tbody>
- </table></div>
- <p>
- The keyword as well as the subject parameters can be any valid spirit parser.
- The parameter n, min and max are integer constants.
- </p>
- <h6>
- <a name="spirit_repository.qi_components.directives.kwd.h4"></a>
- <span class="phrase"><a name="spirit_repository.qi_components.directives.kwd.attributes"></a></span><a class="link" href="kwd.html#spirit_repository.qi_components.directives.kwd.attributes">Attributes</a>
- </h6>
- <div class="informaltable"><table class="table">
- <colgroup>
- <col>
- <col>
- </colgroup>
- <thead><tr>
- <th>
- <p>
- Expression
- </p>
- </th>
- <th>
- <p>
- Attribute
- </p>
- </th>
- </tr></thead>
- <tbody>
- <tr>
- <td>
- <p>
- <code class="computeroutput"><span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k1</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span></code>
- </p>
- </td>
- <td>
- <p>
- </p>
- <pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">a</span><span class="special">:</span> <span class="identifier">A</span> <span class="special">--></span> <span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k1</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]:</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">A</span><span class="special">></span> <span class="keyword">or</span> <span class="identifier">vector</span><span class="special"><</span><span class="identifier">A</span><span class="special">></span>
- <span class="identifier">a</span><span class="special">:</span> <span class="identifier">Unused</span> <span class="special">--></span> <span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k1</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]:</span> <span class="identifier">Unused</span></pre>
- <p>
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="computeroutput"><span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k1</span><span class="special">,</span><span class="identifier">n</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span></code>
- </p>
- </td>
- <td>
- <p>
- </p>
- <pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">a</span><span class="special">:</span> <span class="identifier">A</span> <span class="special">--></span> <span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k1</span><span class="special">,</span><span class="identifier">n</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]:</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">A</span><span class="special">></span> <span class="keyword">or</span> <span class="identifier">vector</span><span class="special"><</span><span class="identifier">A</span><span class="special">></span>
- <span class="identifier">a</span><span class="special">:</span> <span class="identifier">Unused</span> <span class="special">--></span> <span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k1</span><span class="special">,</span><span class="identifier">n</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]:</span> <span class="identifier">Unused</span></pre>
- <p>
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="computeroutput"><span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k1</span><span class="special">,</span><span class="identifier">min</span><span class="special">,</span>
- <span class="identifier">max</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span></code>
- </p>
- </td>
- <td>
- <p>
- </p>
- <pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">a</span><span class="special">:</span> <span class="identifier">A</span> <span class="special">--></span> <span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k1</span><span class="special">,</span><span class="identifier">min</span><span class="special">,</span> <span class="identifier">max</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]:</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">A</span><span class="special">></span> <span class="keyword">or</span> <span class="identifier">vector</span><span class="special"><</span><span class="identifier">A</span><span class="special">></span>
- <span class="identifier">a</span><span class="special">:</span> <span class="identifier">Unused</span> <span class="special">--></span> <span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k1</span><span class="special">,</span><span class="identifier">min</span><span class="special">,</span> <span class="identifier">max</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]:</span> <span class="identifier">Unused</span></pre>
- <p>
- </p>
- </td>
- </tr>
- <tr>
- <td>
- <p>
- <code class="computeroutput"><span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k1</span><span class="special">,</span><span class="identifier">min</span><span class="special">,</span>
- <span class="identifier">inf</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span></code>
- </p>
- </td>
- <td>
- <p>
- </p>
- <pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">a</span><span class="special">:</span> <span class="identifier">A</span> <span class="special">--></span> <span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k1</span><span class="special">,</span><span class="identifier">min</span><span class="special">,</span> <span class="identifier">inf</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]:</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">A</span><span class="special">></span> <span class="keyword">or</span> <span class="identifier">vector</span><span class="special"><</span><span class="identifier">A</span><span class="special">></span>
- <span class="identifier">a</span><span class="special">:</span> <span class="identifier">Unused</span> <span class="special">--></span> <span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k1</span><span class="special">,</span><span class="identifier">min</span><span class="special">,</span> <span class="identifier">inf</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]:</span> <span class="identifier">Unused</span></pre>
- <p>
- </p>
- </td>
- </tr>
- </tbody>
- </table></div>
- <h6>
- <a name="spirit_repository.qi_components.directives.kwd.h5"></a>
- <span class="phrase"><a name="spirit_repository.qi_components.directives.kwd.complexity"></a></span><a class="link" href="kwd.html#spirit_repository.qi_components.directives.kwd.complexity">Complexity</a>
- </h6>
- <div class="blockquote"><blockquote class="blockquote">
- <p>
- The overall complexity is defined by the complexity of its subject parser.
- The complexity of the keyword list construct <code class="computeroutput"><span class="identifier">kwd</span></code>
- itself is O(N), where N is the number of repetitions executed.
- </p>
- <p>
- In the case where all the keywords are strings, the complexity of the
- keyword list itself determined by the complexity of the internal TST
- contents :
- </p>
- <p>
- O(log n+k)
- </p>
- <p>
- Where k is the length of the string to be searched in a TST with n strings.
- </p>
- <p>
- When the keywords used are complex parsers, then the complexity is the
- sum of the sub parser complexities.
- </p>
- </blockquote></div>
- <h6>
- <a name="spirit_repository.qi_components.directives.kwd.h6"></a>
- <span class="phrase"><a name="spirit_repository.qi_components.directives.kwd.example"></a></span><a class="link" href="kwd.html#spirit_repository.qi_components.directives.kwd.example">Example</a>
- </h6>
- <p>
- Please refer to keyword_list.
- </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 © 2001-2011 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>
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