libs/spirit/repository/doc/html/spirit_repository/qi_components/operators/keyword_list.html


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<title>Keyword List Operator</title>
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<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="spirit_repository.qi_components.operators.keyword_list"></a><a class="link" href="keyword_list.html" title="Keyword List Operator">Keyword
        List Operator</a>
</h4></div></div></div>
<h6>
<a name="spirit_repository.qi_components.operators.keyword_list.h0"></a>
          <span><a name="spirit_repository.qi_components.operators.keyword_list.description"></a></span><a class="link" href="keyword_list.html#spirit_repository.qi_components.operators.keyword_list.description">Description</a>
        </h6>
<p>
          The keyword list operator, <code class="computeroutput"><span class="identifier">kwd</span><span class="special">(</span><span class="string">"k1"</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span>
          <span class="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="string">"k2"</span><span class="special">)[</span><span class="identifier">b</span><span class="special">]</span></code>,
          works tightly with the kwd, ikwd directives to effeciently match keyword
          lists. As long as one of the keywords specified through the kwd or ikwd
          directive matches, the keyword will be immediatly followed by the the keyword's
          associated subject parser. The parser will continue parsing input as long
          as the one of the keywords and it's associated parser succeed. Writing
          : (kwd("k1")[a] / kwd("k2")[b] / ... ) is equivalent
          to: *( "k1" &gt; a | "k2" &gt; b ... ).
        </p>
<h6>
<a name="spirit_repository.qi_components.operators.keyword_list.h1"></a>
          <span><a name="spirit_repository.qi_components.operators.keyword_list.header"></a></span><a class="link" href="keyword_list.html#spirit_repository.qi_components.operators.keyword_list.header">Header</a>
        </h6>
<pre class="programlisting"><span class="comment">// forwards to &lt;boost/spirit/repository/home/qi/operator/keywords.hpp&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">repository</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">qi_keywords</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
</pre>
<h6>
<a name="spirit_repository.qi_components.operators.keyword_list.h2"></a>
          <span><a name="spirit_repository.qi_components.operators.keyword_list.expression_semantics"></a></span><a class="link" href="keyword_list.html#spirit_repository.qi_components.operators.keyword_list.expression_semantics">Expression
          Semantics</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">k1</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span>
                    <span class="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k2</span><span class="special">)[</span><span class="identifier">b</span><span class="special">]</span></code>
                  </p>
                </td>
<td>
                  <p>
                    Match <code class="computeroutput"><span class="identifier">lit</span><span class="special">(</span><span class="identifier">k1</span><span class="special">)</span>
                    <span class="special">&gt;</span> <span class="identifier">a</span></code>
                    or <code class="computeroutput"><span class="identifier">lit</span><span class="special">(</span><span class="identifier">k2</span><span class="special">)</span>
                    <span class="special">&gt;</span> <span class="identifier">b</span></code>,
                    equivalent to <code class="computeroutput"><span class="identifier">lit</span><span class="special">(</span><span class="identifier">k1</span><span class="special">)</span> <span class="special">&gt;</span>
                    <span class="identifier">a</span> <span class="special">|</span>
                    <span class="identifier">lit</span><span class="special">(</span><span class="identifier">k2</span><span class="special">)</span>
                    <span class="special">&gt;</span> <span class="identifier">b</span></code>
                  </p>
                </td>
</tr></tbody>
</table></div>
<h6>
<a name="spirit_repository.qi_components.operators.keyword_list.h3"></a>
          <span><a name="spirit_repository.qi_components.operators.keyword_list.attributes"></a></span><a class="link" href="keyword_list.html#spirit_repository.qi_components.operators.keyword_list.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="string">"k1"</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span>
                    <span class="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="string">"k2"</span><span class="special">)[</span><span class="identifier">b</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">b</span><span class="special">:</span> <span class="identifier">B</span> <span class="special">--&gt;</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="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k2</span><span class="special">)[</span><span class="identifier">b</span><span class="special">]):</span> <span class="identifier">tuple</span><span class="special">&lt;</span><span class="identifier">A</span><span class="special">,</span> <span class="identifier">B</span><span class="special">&gt;</span>
<span class="identifier">a</span><span class="special">:</span> <span class="identifier">A</span><span class="special">,</span> <span class="identifier">b</span><span class="special">:</span> <span class="identifier">Unused</span> <span class="special">--&gt;</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="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k2</span><span class="special">)[</span><span class="identifier">b</span><span class="special">]):</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">A</span><span class="special">&gt;</span>
<span class="identifier">a</span><span class="special">:</span> <span class="identifier">Unused</span><span class="special">,</span> <span class="identifier">b</span><span class="special">:</span> <span class="identifier">B</span> <span class="special">--&gt;</span> <span class="special">(</span><span class="identifier">kwd</span><span class="special">(</span><span class="string">"k1"</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span> <span class="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k2</span><span class="special">)[</span><span class="identifier">b</span><span class="special">]):</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">B</span><span class="special">&gt;</span>
<span class="identifier">a</span><span class="special">:</span> <span class="identifier">Unused</span><span class="special">,</span> <span class="identifier">b</span><span class="special">:</span> <span class="identifier">Unused</span> <span class="special">--&gt;</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="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k2</span><span class="special">)[</span><span class="identifier">b</span><span class="special">]):</span> <span class="identifier">Unused</span>

<span class="identifier">a</span><span class="special">:</span> <span class="identifier">A</span><span class="special">,</span> <span class="identifier">b</span><span class="special">:</span> <span class="identifier">A</span> <span class="special">--&gt;(</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="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k2</span><span class="special">)[</span><span class="identifier">b</span><span class="special">]):</span> <span class="identifier">tuple</span><span class="special">&lt;</span><span class="identifier">A</span><span class="special">,</span> <span class="identifier">A</span><span class="special">&gt;</span></pre>
<p>
                  </p>
                </td>
</tr></tbody>
</table></div>
<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>
            The keyword list parser works tightly with the kwd and ikwd directives
            and can't be used without it. A compile time error will warn you of any
            mistakes. This parser collects all the kwd directives and extracts the
            keyword literals from the directives to internaly build a Ternary Search
            Tree (TST) to effectively parse the keywords. Because you we can't mix
            character types inside a TST you must take care not to mix wide strings
            with normal strings in the keyword you supply to a keyword list. Should
            it happen the compiler will trap the mistake for you.
          </p></td></tr>
</table></div>
<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>
            The kwd directive also works a bit like the repeat directive and can
            be used to formulate additional contraints on the number of times a keyword
            can occur while parsing a keyword list.
          </p></td></tr>
</table></div>
<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>
            The kwd and ikwd directives can be mixed inside a keyword list. This
            has however a small overhead and should be avoided when possible.
          </p></td></tr>
</table></div>
<h6>
<a name="spirit_repository.qi_components.operators.keyword_list.h4"></a>
          <span><a name="spirit_repository.qi_components.operators.keyword_list.complexity"></a></span><a class="link" href="keyword_list.html#spirit_repository.qi_components.operators.keyword_list.complexity">Complexity</a>
        </h6>
<div class="blockquote"><blockquote class="blockquote">
<p>
            The overall complexity of the keyword list parser is defined by the sum
            of the complexities of its elements. The complexity of the keyword list
            itself is 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>
</blockquote></div>
<h6>
<a name="spirit_repository.qi_components.operators.keyword_list.h5"></a>
          <span><a name="spirit_repository.qi_components.operators.keyword_list.example"></a></span><a class="link" href="keyword_list.html#spirit_repository.qi_components.operators.keyword_list.example">Example</a>
        </h6>
<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>
            The test harness for the example(s) below is presented in the <a href="../../../../../../doc/html/spirit/qi/reference/basics.html#spirit.qi.reference.basics.examples" target="_top">Basics
            Examples</a> section.
          </p></td></tr>
</table></div>
<p>
          Declare a small data structure representing a person:
        </p>
<p>
</p>
<pre class="programlisting"><span class="comment">// Data structure definitions to test the kwd directive</span>
<span class="comment">// and the keywords list operator</span>

<span class="keyword">struct</span> <span class="identifier">person</span> <span class="special">{</span>
    <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">name</span><span class="special">;</span>
    <span class="keyword">int</span> <span class="identifier">age</span><span class="special">;</span>
    <span class="keyword">double</span> <span class="identifier">size</span><span class="special">;</span>
    <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&gt;</span> <span class="identifier">favorite_colors</span><span class="special">;</span>

<span class="special">};</span>

<span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span> <span class="special">&amp;</span><span class="keyword">operator</span><span class="special">&lt;&lt;(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span> <span class="special">&amp;</span><span class="identifier">os</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">person</span> <span class="special">&amp;</span><span class="identifier">p</span><span class="special">)</span>
<span class="special">{</span>
    <span class="identifier">os</span><span class="special">&lt;&lt;</span><span class="string">"Person : "</span><span class="special">&lt;&lt;</span><span class="identifier">p</span><span class="special">.</span><span class="identifier">name</span><span class="special">&lt;&lt;</span><span class="string">", "</span><span class="special">&lt;&lt;</span><span class="identifier">p</span><span class="special">.</span><span class="identifier">age</span><span class="special">&lt;&lt;</span><span class="string">", "</span><span class="special">&lt;&lt;</span><span class="identifier">p</span><span class="special">.</span><span class="identifier">size</span><span class="special">&lt;&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
    <span class="identifier">std</span><span class="special">::</span><span class="identifier">copy</span><span class="special">(</span><span class="identifier">p</span><span class="special">.</span><span class="identifier">favorite_colors</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span><span class="identifier">p</span><span class="special">.</span><span class="identifier">favorite_colors</span><span class="special">.</span><span class="identifier">end</span><span class="special">(),</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream_iterator</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&gt;(</span><span class="identifier">os</span><span class="special">,</span><span class="string">"\n"</span><span class="special">));</span>
    <span class="keyword">return</span> <span class="identifier">os</span><span class="special">;</span>
<span class="special">}</span>

<span class="identifier">BOOST_FUSION_ADAPT_STRUCT</span><span class="special">(</span> <span class="identifier">person</span><span class="special">,</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">name</span><span class="special">)</span>
    <span class="special">(</span><span class="keyword">int</span><span class="special">,</span> <span class="identifier">age</span><span class="special">)</span>
    <span class="special">(</span><span class="keyword">double</span><span class="special">,</span> <span class="identifier">size</span><span class="special">)</span>
    <span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&gt;,</span> <span class="identifier">favorite_colors</span><span class="special">)</span>
<span class="special">)</span>
</pre>
<p>
        </p>
<p>
          Some using declarations:
        </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">repository</span><span class="special">::</span><span class="identifier">qi</span><span class="special">::</span><span class="identifier">kwd</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">inf</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_type</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">qi</span><span class="special">::</span><span class="identifier">double_</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">int_</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">rule</span><span class="special">;</span>
</pre>
<p>
        </p>
<p>
          Now let's declare a keyword parser:
        </p>
<p>
</p>
<pre class="programlisting"><span class="identifier">no_constraint_person_rule</span> <span class="special">%=</span>
    <span class="identifier">kwd</span><span class="special">(</span><span class="string">"name"</span><span class="special">)[</span><span class="char">'='</span> <span class="special">&gt;</span> <span class="identifier">parse_string</span> <span class="special">]</span>
  <span class="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="string">"age"</span><span class="special">)</span>   <span class="special">[</span><span class="char">'='</span> <span class="special">&gt;</span> <span class="identifier">int_</span><span class="special">]</span>
  <span class="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="string">"size"</span><span class="special">)</span>   <span class="special">[</span><span class="char">'='</span> <span class="special">&gt;</span> <span class="identifier">double_</span> <span class="special">&gt;</span> <span class="char">'m'</span><span class="special">]</span>
  <span class="special">;</span>
</pre>
<p>
        </p>
<p>
          A couple of input string variations run on the same parser:
        </p>
<p>
          Parsing a keyword list:
        </p>
<p>
</p>
<pre class="programlisting"><span class="comment">// Let's declare a small list of people for which we want to collect information.</span>
<span class="identifier">person</span> <span class="identifier">John</span><span class="special">,</span><span class="identifier">Mary</span><span class="special">,</span><span class="identifier">Mike</span><span class="special">,</span><span class="identifier">Hellen</span><span class="special">,</span><span class="identifier">Johny</span><span class="special">;</span>
<span class="identifier">test_phrase_parser_attr</span><span class="special">(</span>
                <span class="string">"name = \"John\" \n age = 10 \n size = 1.69m "</span>
                <span class="special">,</span><span class="identifier">no_constraint_person_rule</span>
                <span class="special">,</span><span class="identifier">John</span><span class="special">);</span>  <span class="comment">// full in orginal order</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span><span class="special">&lt;&lt;</span><span class="identifier">John</span><span class="special">;</span>

<span class="identifier">test_phrase_parser_attr</span><span class="special">(</span>
                <span class="string">"age = 10 \n size = 1.69m \n name = \"Mary\""</span>
                <span class="special">,</span><span class="identifier">no_constraint_person_rule</span>
                <span class="special">,</span><span class="identifier">Mary</span><span class="special">);</span>  <span class="comment">// keyword oder doesn't matter</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span><span class="special">&lt;&lt;</span><span class="identifier">Mary</span><span class="special">;</span>

<span class="identifier">test_phrase_parser_attr</span><span class="special">(</span>
                 <span class="string">"size = 1.69m \n name = \"Mike\" \n age = 10 "</span>
                <span class="special">,</span><span class="identifier">no_constraint_person_rule</span>
                <span class="special">,</span><span class="identifier">Mike</span><span class="special">);</span>  <span class="comment">// still the same result</span>

<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span><span class="special">&lt;&lt;</span><span class="identifier">Mike</span><span class="special">;</span>
</pre>
<p>
        </p>
<p>
          The code above will print:
        </p>
<pre class="programlisting">Person : John, 10, 1.69
Person : Mary, 10, 1.69
Person : Mike, 10, 1.69
</pre>
<p>
          Now let's delcare a parser with some occurence constraints:
        </p>
<p>
          The parser definition below uses the kwd directive occurence constraint
          variants to make sure that the name and age keyword occur only once and
          allows the favorite color entry to appear 0 or more times.
        </p>
<p>
</p>
<pre class="programlisting"><span class="identifier">constraint_person_rule</span> <span class="special">%=</span>
    <span class="identifier">kwd</span><span class="special">(</span><span class="string">"name"</span><span class="special">,</span><span class="number">1</span><span class="special">)</span>                 <span class="special">[</span><span class="char">'='</span> <span class="special">&gt;</span> <span class="identifier">parse_string</span> <span class="special">]</span>
  <span class="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="string">"age"</span>   <span class="special">,</span><span class="number">1</span><span class="special">)</span>                 <span class="special">[</span><span class="char">'='</span> <span class="special">&gt;</span> <span class="identifier">int_</span><span class="special">]</span>
  <span class="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="string">"size"</span>   <span class="special">,</span><span class="number">1</span><span class="special">)</span>                 <span class="special">[</span><span class="char">'='</span> <span class="special">&gt;</span> <span class="identifier">double_</span> <span class="special">&gt;</span> <span class="char">'m'</span><span class="special">]</span>
  <span class="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="string">"favorite color"</span><span class="special">,</span><span class="number">0</span><span class="special">,</span><span class="identifier">inf</span><span class="special">)</span> <span class="special">[</span> <span class="char">'='</span> <span class="special">&gt;</span> <span class="identifier">parse_string</span> <span class="special">]</span>
  <span class="special">;</span>
</pre>
<p>
        </p>
<p>
          And see how it works in these two cases:
        </p>
<p>
</p>
<pre class="programlisting"> <span class="comment">// Here all the give constraint are resepected : parsing will succeed.</span>
 <span class="identifier">test_phrase_parser_attr</span><span class="special">(</span>
     <span class="string">"name = \"Hellen\" \n age = 10 \n size = 1.80m \n favorite color = \"blue\" \n favorite color = \"green\" "</span>
     <span class="special">,</span><span class="identifier">constraint_person_rule</span>
     <span class="special">,</span><span class="identifier">Hellen</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="identifier">Hellen</span><span class="special">;</span>

<span class="comment">// Parsing this string will fail because the age and size minimum occurence requirements aren't met.</span>
<span class="identifier">test_phrase_parser_attr</span><span class="special">(</span>
     <span class="string">"name = \"Johny\"  \n favorite color = \"blue\" \n favorite color = \"green\" "</span>
     <span class="special">,</span><span class="identifier">constraint_person_rule</span>
     <span class="special">,</span><span class="identifier">Johny</span> <span class="special">);</span>
</pre>
<p>
        </p>
<p>
          Parsing the first string will succeed but fail for the second string as
          the occurence constraints aren't met. This code should print:
        </p>
<pre class="programlisting">Person : Hellen, 10, 1.8
blue
green
</pre>
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