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| 26 | <a name="boost.xpressive.before"></a><div class="titlepage"></div> |
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| 27 | <div class="refnamediv"> |
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| 28 | <h2><span class="refentrytitle">Function template before</span></h2> |
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| 29 | <p>boost::xpressive::before — Look-ahead assertion. </p> |
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| 30 | </div> |
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| 31 | <h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> |
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| 32 | <div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"> |
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| 33 | <span class="bold"><strong>template</strong></span><<span class="bold"><strong>typename</strong></span> Xpr> <span class="type"><span class="emphasis"><em>unspecified</em></span></span> before(Xpr <span class="bold"><strong>const</strong></span> & xpr);</pre></div> |
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| 34 | <div class="refsect1" lang="en"> |
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| 35 | <a name="id2045983"></a><h2>Description</h2> |
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| 36 | <p>before(xpr) succeeds if the xpr sub-expression would match at the current position in the sequence, but xpr is not included in the match. For instance, before("foo") succeeds if we are before a "foo". Look-ahead assertions can be negated with the bit-compliment operator.</p> |
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| 45 | <span class="term">Parameters:</span></td> |
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| 46 | <td><div class="variablelist"><table border="0"> |
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| 47 | <col align="left" valign="top"> |
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| 48 | <tbody><tr> |
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| 49 | <td> |
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| 50 | <span class="term"><code class="computeroutput">xpr</code></span></td> |
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| 51 | <td><p>The sub-expression to put in the look-ahead assertion. </p></td> |
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| 52 | </tr></tbody> |
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| 53 | </table></div></td> |
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| 54 | </tr> |
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| 55 | <tr> |
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| 56 | <td> |
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| 57 | <span class="term">Notes:</span></td> |
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| 58 | <td><p>before(xpr) is equivalent to the perl (?=...) extension. ~before(xpr) is a negative look-ahead assertion, equivalent to the perl (?!...) extension.</p></td> |
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| 59 | </tr> |
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| 66 | <td align="right"><small>Copyright © 2003, 2004 Eric Niebler</small></td> |
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