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<div class="titlepage"><div><div><h3 class="title">
<a name="boost_regex.syntax.leftmost_longest_rule"></a><a class="link" href="leftmost_longest_rule.html" title="The Leftmost Longest Rule">The Leftmost
      Longest Rule</a>
</h3></div></div></div>
<p>
        Often there is more than one way of matching a regular expression at a particular
        location, for POSIX basic and extended regular expressions, the "best"
        match is determined as follows:
      </p>
<div class="orderedlist"><ol class="orderedlist" type="1">
<li class="listitem">
            Find the leftmost match, if there is only one match possible at this
            location then return it.
          </li>
<li class="listitem">
            Find the longest of the possible matches, along with any ties. If there
            is only one such possible match then return it.
          </li>
<li class="listitem">
            If there are no marked sub-expressions, then all the remaining alternatives
            are indistinguishable; return the first of these found.
          </li>
<li class="listitem">
            Find the match which has matched the first sub-expression in the leftmost
            position, along with any ties. If there is only on such match possible
            then return it.
          </li>
<li class="listitem">
            Find the match which has the longest match for the first sub-expression,
            along with any ties. If there is only one such match then return it.
          </li>
<li class="listitem">
            Repeat steps 4 and 5 for each additional marked sub-expression.
          </li>
<li class="listitem">
            If there is still more than one possible match remaining, then they are
            indistinguishable; return the first one found.
          </li>
</ol></div>
</div>
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<td align="right"><div class="copyright-footer">Copyright &#169; 1998-2013 John Maddock<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>
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	24	</div>
	25	<div class="section">
	26	<div class="titlepage"><div><div><h3 class="title">
	27	<a name="boost_regex.syntax.leftmost_longest_rule"></a><a class="link" href="leftmost_longest_rule.html" title="The Leftmost Longest Rule">The Leftmost
	28	Longest Rule</a>
	29	</h3></div></div></div>
	30	<p>
	31	Often there is more than one way of matching a regular expression at a particular
	32	location, for POSIX basic and extended regular expressions, the "best"
	33	match is determined as follows:
	34	</p>
	35	<div class="orderedlist"><ol class="orderedlist" type="1">
	36	<li class="listitem">
	37	Find the leftmost match, if there is only one match possible at this
	38	location then return it.
	39	</li>
	40	<li class="listitem">
	41	Find the longest of the possible matches, along with any ties. If there
	42	is only one such possible match then return it.
	43	</li>
	44	<li class="listitem">
	45	If there are no marked sub-expressions, then all the remaining alternatives
	46	are indistinguishable; return the first of these found.
	47	</li>
	48	<li class="listitem">
	49	Find the match which has matched the first sub-expression in the leftmost
	50	position, along with any ties. If there is only on such match possible
	51	then return it.
	52	</li>
	53	<li class="listitem">
	54	Find the match which has the longest match for the first sub-expression,
	55	along with any ties. If there is only one such match then return it.
	56	</li>
	57	<li class="listitem">
	58	Repeat steps 4 and 5 for each additional marked sub-expression.
	59	</li>
	60	<li class="listitem">
	61	If there is still more than one possible match remaining, then they are
	62	indistinguishable; return the first one found.
	63	</li>
	64	</ol></div>
65	</div>
66	<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
67	<td align="left"></td>
68	<td align="right"><div class="copyright-footer">Copyright © 1998-2013 John Maddock<p>
69	Distributed under the Boost Software License, Version 1.0. (See accompanying
70	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>)
71	</p>
72	</div></td>
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