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| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="spirit.qi.tutorials.number_list_attribute___one_more__with_style"></a><a class="link" href="number_list_attribute___one_more__with_style.html" title="Number List Attribute - one more, with style">Number |
| List Attribute - one more, with style</a> |
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| <p> |
| You've seen that the <code class="computeroutput"><span class="identifier">double_</span></code> |
| parser has a <code class="computeroutput"><span class="keyword">double</span></code> attribute. |
| All parsers have an attribute, even complex parsers. Those that are composed |
| from primitives using operators, like the list parser, also have an attribute. |
| It so happens that the attribute of a list parser: |
| </p> |
| <pre class="programlisting"><span class="identifier">p</span> <span class="special">%</span> <span class="identifier">d</span> |
| </pre> |
| <p> |
| is a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span></code> of the attribute of <code class="computeroutput"><span class="identifier">p</span></code>. So, for our parser: |
| </p> |
| <pre class="programlisting"><span class="identifier">double_</span> <span class="special">%</span> <span class="char">','</span> |
| </pre> |
| <p> |
| we'll have an attribute of: |
| </p> |
| <pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> |
| </pre> |
| <p> |
| So, what does this give us? Well, we can simply pass in a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span></code> |
| to our number list parser and it will happily churn out our result in our |
| vector. For that to happen, we'll use a variation of the <code class="computeroutput"><span class="identifier">phrase_parse</span></code> with an additional argument: |
| the parser's attribute. With the following arguments passed to <code class="computeroutput"><span class="identifier">phrase_parse</span></code> |
| </p> |
| <div class="orderedlist"><ol class="orderedlist" type="1"> |
| <li class="listitem"> |
| An iterator pointing to the start of the input |
| </li> |
| <li class="listitem"> |
| An iterator pointing to one past the end of the input |
| </li> |
| <li class="listitem"> |
| The parser object |
| </li> |
| <li class="listitem"> |
| Another parser called the skip parser |
| </li> |
| <li class="listitem"> |
| The parser's attribute |
| </li> |
| </ol></div> |
| <p> |
| our parser now is further simplified to: |
| </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_numbers</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">vector</span><span class="special"><</span><span class="keyword">double</span><span class="special">>&</span> <span class="identifier">v</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">using</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">qi</span><span class="special">::</span><span class="identifier">phrase_parse</span><span class="special">;</span> |
| <span class="keyword">using</span> <span class="identifier">qi</span><span class="special">::</span><span class="identifier">_1</span><span class="special">;</span> |
| <span class="keyword">using</span> <span class="identifier">ascii</span><span class="special">::</span><span class="identifier">space</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="comment">// Begin grammar |
| </span> <span class="special">(</span> |
| <span class="identifier">double_</span> <span class="special">%</span> <span class="char">','</span> |
| <span class="special">)</span> |
| <span class="special">,</span> |
| <span class="comment">// End grammar |
| </span> |
| <span class="identifier">space</span><span class="special">,</span> <span class="identifier">v</span><span class="special">);</span> |
| |
| <span class="keyword">if</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> |
| The full cpp file for this example can be found here: <a href="../../../../../example/qi/num_list4.cpp" target="_top">../../example/qi/num_list4.cpp</a> |
| </p> |
| <p> |
| <span class="bold"><strong>Hey, no more actions!!!</strong></span> Now we're entering |
| the realm of attribute grammars. Cool eh? |
| </p> |
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| <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>) |
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