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| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="spirit.qi.reference.operator.sequential_or"></a><a class="link" href="sequential_or.html" title="Sequential Or (a || b)">Sequential |
| Or (<code class="computeroutput"><span class="identifier">a</span> <span class="special">||</span> |
| <span class="identifier">b</span></code>)</a> |
| </h5></div></div></div> |
| <a name="spirit.qi.reference.operator.sequential_or.description"></a><h6> |
| <a name="id943155"></a> |
| <a class="link" href="sequential_or.html#spirit.qi.reference.operator.sequential_or.description">Description</a> |
| </h6> |
| <p> |
| The sequential-or operator, <code class="computeroutput"><span class="identifier">a</span> |
| <span class="special">||</span> <span class="identifier">b</span></code>, |
| matches <code class="computeroutput"><span class="identifier">a</span></code> or <code class="computeroutput"><span class="identifier">b</span></code> or <code class="computeroutput"><span class="identifier">a</span></code> |
| followed by <code class="computeroutput"><span class="identifier">b</span></code>. That is, |
| if both <code class="computeroutput"><span class="identifier">a</span></code> and <code class="computeroutput"><span class="identifier">b</span></code> match, it must be in sequence; this |
| is equivalent to <code class="computeroutput"><span class="identifier">a</span> <span class="special">>></span> |
| <span class="special">-</span><span class="identifier">b</span> |
| <span class="special">|</span> <span class="identifier">b</span></code>: |
| </p> |
| <pre class="programlisting"><span class="identifier">a</span> <span class="special">||</span> <span class="identifier">b</span> <span class="special">||</span> <span class="special">...</span> |
| </pre> |
| <a name="spirit.qi.reference.operator.sequential_or.header"></a><h6> |
| <a name="id943290"></a> |
| <a class="link" href="sequential_or.html#spirit.qi.reference.operator.sequential_or.header">Header</a> |
| </h6> |
| <pre class="programlisting"><span class="comment">// forwards to <boost/spirit/home/qi/operator/sequential_or.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">include</span><span class="special">/</span><span class="identifier">qi_sequential_or</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| </pre> |
| <p> |
| Also, see <a class="link" href="../../../structure/include.html" title="Include">Include Structure</a>. |
| </p> |
| <a name="spirit.qi.reference.operator.sequential_or.model_of"></a><h6> |
| <a name="id943364"></a> |
| <a class="link" href="sequential_or.html#spirit.qi.reference.operator.sequential_or.model_of">Model |
| of</a> |
| </h6> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| <a class="link" href="../parser_concepts/naryparser.html" title="NaryParser"><code class="computeroutput"><span class="identifier">NaryParser</span></code></a> |
| </p></blockquote></div> |
| <div class="variablelist"> |
| <p class="title"><b>Notation</b></p> |
| <dl> |
| <dt><span class="term"><code class="computeroutput"><span class="identifier">a</span></code>, <code class="computeroutput"><span class="identifier">b</span></code></span></dt> |
| <dd><p> |
| A <a class="link" href="../parser_concepts/parser.html" title="Parser"><code class="computeroutput"><span class="identifier">Parser</span></code></a> |
| </p></dd> |
| </dl> |
| </div> |
| <a name="spirit.qi.reference.operator.sequential_or.expression_semantics"></a><h6> |
| <a name="id943440"></a> |
| <a class="link" href="sequential_or.html#spirit.qi.reference.operator.sequential_or.expression_semantics">Expression |
| Semantics</a> |
| </h6> |
| <p> |
| Semantics of an expression is defined only where it differs from, or |
| is not defined in <a class="link" href="../parser_concepts/naryparser.html" title="NaryParser"><code class="computeroutput"><span class="identifier">NaryParser</span></code></a>. |
| </p> |
| <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">a</span> <span class="special">||</span> |
| <span class="identifier">b</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Match <code class="computeroutput"><span class="identifier">a</span></code> or |
| <code class="computeroutput"><span class="identifier">b</span></code> in sequence. |
| equivalent to <code class="computeroutput"><span class="identifier">a</span> <span class="special">>></span> <span class="special">-</span><span class="identifier">b</span> <span class="special">|</span> |
| <span class="identifier">b</span></code> |
| </p> |
| </td> |
| </tr></tbody> |
| </table></div> |
| <a name="spirit.qi.reference.operator.sequential_or.attributes"></a><h6> |
| <a name="id943582"></a> |
| <a class="link" href="sequential_or.html#spirit.qi.reference.operator.sequential_or.attributes">Attributes</a> |
| </h6> |
| <p> |
| See <a class="link" href="../../quick_reference/compound_attribute_rules.html#spirit.qi.quick_reference.compound_attribute_rules.notation">Compound |
| Attribute Notation</a>. |
| </p> |
| <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">a</span> <span class="special">||</span> |
| <span class="identifier">b</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">--></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">tuple</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="identifier">optional</span><span class="special"><</span><span class="identifier">B</span><span class="special">></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">b</span><span class="special">:</span> <span class="identifier">Unused</span> <span class="special">--></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">optional</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">b</span><span class="special">:</span> <span class="identifier">B</span> <span class="special">--></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">optional</span><span class="special"><</span><span class="identifier">B</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">b</span><span class="special">:</span> <span class="identifier">Unused</span> <span class="special">--></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="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">--></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">vector</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="special">></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 sequential-or parser behaves attribute-wise very similar to the |
| plain sequence parser (<code class="computeroutput"><span class="identifier">a</span> |
| <span class="special">>></span> <span class="identifier">b</span></code>) |
| in the sense that it exposes the attributes of its elements separately. |
| For instance, if you attach a semantic action to the whole sequential-or: |
| |
| </p> |
| <pre class="programlisting"><span class="special">(</span><span class="identifier">int_</span> <span class="special">||</span> <span class="identifier">int_</span><span class="special">)[</span><span class="identifier">print_pair</span><span class="special">(</span><span class="identifier">_1</span><span class="special">,</span> <span class="identifier">_2</span><span class="special">)]</span> |
| </pre> |
| <p> |
| the function object <code class="computeroutput"><span class="identifier">print_pair</span></code> |
| would be invoked with the attribute of the first <code class="computeroutput"><span class="identifier">int_</span></code> |
| (<code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span></code>) |
| as its first parameter and the attribute of the second <code class="computeroutput"><span class="identifier">int_</span></code> (<code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span></code> as well) as its second parameter. |
| </p> |
| </td></tr> |
| </table></div> |
| <a name="spirit.qi.reference.operator.sequential_or.complexity"></a><h6> |
| <a name="id944211"></a> |
| <a class="link" href="sequential_or.html#spirit.qi.reference.operator.sequential_or.complexity">Complexity</a> |
| </h6> |
| <div class="blockquote"><blockquote class="blockquote"><p> |
| The overall complexity of the sequential-or parser is defined by the |
| sum of the complexities of its elements. The complexity of the sequential-or |
| itself is O(N), where N is the number of elements in the sequence. |
| </p></blockquote></div> |
| <a name="spirit.qi.reference.operator.sequential_or.example"></a><h6> |
| <a name="id944232"></a> |
| <a class="link" href="sequential_or.html#spirit.qi.reference.operator.sequential_or.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 class="link" href="../basics.html#spirit.qi.reference.basics.examples">Basics Examples</a> |
| section. |
| </p></td></tr> |
| </table></div> |
| <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">qi</span><span class="special">::</span><span class="identifier">int_</span><span class="special">;</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| Correctly parsing a number with optional fractional digits: |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="identifier">test_parser</span><span class="special">(</span><span class="string">"123.456"</span><span class="special">,</span> <span class="identifier">int_</span> <span class="special">||</span> <span class="special">(</span><span class="char">'.'</span> <span class="special">>></span> <span class="identifier">int_</span><span class="special">));</span> <span class="comment">// full |
| </span><span class="identifier">test_parser</span><span class="special">(</span><span class="string">"123"</span><span class="special">,</span> <span class="identifier">int_</span> <span class="special">||</span> <span class="special">(</span><span class="char">'.'</span> <span class="special">>></span> <span class="identifier">int_</span><span class="special">));</span> <span class="comment">// just the whole number |
| </span><span class="identifier">test_parser</span><span class="special">(</span><span class="string">".456"</span><span class="special">,</span> <span class="identifier">int_</span> <span class="special">||</span> <span class="special">(</span><span class="char">'.'</span> <span class="special">>></span> <span class="identifier">int_</span><span class="special">));</span> <span class="comment">// just the fraction</span></pre> |
| <p> |
| </p> |
| <p> |
| A naive but incorrect solution would try to do this using optionals (e.g.): |
| </p> |
| <pre class="programlisting"><span class="identifier">int_</span> <span class="special">>></span> <span class="special">-(</span><span class="char">'.'</span> <span class="special">>></span> <span class="identifier">int_</span><span class="special">)</span> <span class="comment">// will not match ".456" |
| </span><span class="special">-</span><span class="identifier">int_</span> <span class="special">>></span> <span class="special">(</span><span class="char">'.'</span> <span class="special">>></span> <span class="identifier">int_</span><span class="special">)</span> <span class="comment">// will not match "123" |
| </span><span class="special">-</span><span class="identifier">int_</span> <span class="special">>></span> <span class="special">-(</span><span class="char">'.'</span> <span class="special">>></span> <span class="identifier">int_</span><span class="special">)</span> <span class="comment">// will match empty strings! Ooops. |
| </span></pre> |
| </div> |
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| <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>) |
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