forked from boostorg/regex
66 lines
3.1 KiB
HTML
66 lines
3.1 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<html>
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<head>
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<title>Boost.Regex: Index</title>
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<link rel="stylesheet" type="text/css" href="../../../boost.css">
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</head>
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<body>
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<P>
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<TABLE id="Table1" cellSpacing="1" cellPadding="1" width="100%" border="0">
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<TR>
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<td valign="top" width="300">
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<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../boost.png" border="0"></a></h3>
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</td>
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<TD width="353">
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<H1 align="center">Boost.Regex</H1>
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<H2 align="center">The "Leftmost Longest" Rule</H2>
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</TD>
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<td width="50">
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<h3><a href="index.html"><img height="45" width="43" alt="Boost.Regex Index" src="uarrow.gif" border="0"></a></h3>
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</td>
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</TR>
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</TABLE>
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</P>
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<HR>
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<p></p>
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<P>Often there is more that one way of matching a regular expression at a
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particular location, for POSIX basic and extended regular expressions, the
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"best" match is determined as follows:</P>
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<OL>
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<LI>
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Find the leftmost match, if there is only one match possible at this location
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then return it.</LI>
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<LI>
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Find the longest of the possible matches, along with any ties. If there
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is only one such possible match then return it.</LI>
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<LI>
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If there are no marked sub-expressions, then all the remaining alternatives are
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indistinguishable; return the first of these found.</LI>
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<LI>
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Find the match which has matched the first sub-expression in the leftmost
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position, along with any ties. If there is only on such match possible
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then return it.</LI>
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<LI>
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Find the match which has the longest match for the first sub-expression, along
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with any ties. If there is only one such match then return it.</LI>
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<LI>
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Repeat steps 3 and 4 for each additional marked sub-expression.</LI>
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<LI>
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If there is still more than one possible match remaining, then they are
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indistinguishable; return the first one found.</LI></OL>
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<P>
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<HR>
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<P></P>
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<p>Revised
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<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
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16 Dec 2004</p>
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<p><i><EFBFBD> Copyright John Maddock 1998-
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<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%Y" startspan --> 2003<!--webbot bot="Timestamp" endspan i-checksum="39359" --></i></p>
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<P><I>Use, modification and distribution are subject to the Boost Software License,
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Version 1.0. (See accompanying file <A href="../../../LICENSE_1_0.txt">LICENSE_1_0.txt</A>
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or copy at <A href="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</A>)</I></P>
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</body>
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</html>
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