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pcre-8.35.tar.bz2

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Sergei Golubchik
2014-06-05 13:44:44 +02:00
parent 8958f8b823
commit 8cc5973f1a
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pcre/doc/html/pcrepattern.html
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@ -1003,7 +1003,9 @@ matches "foobar", the first substring is still set to "foo".
<P>
Perl documents that the use of \K within assertions is "not well defined". In
PCRE, \K is acted upon when it occurs inside positive assertions, but is
ignored in negative assertions.
ignored in negative assertions. Note that when a pattern such as (?=ab\K)
matches, the reported start of the match can be greater than the end of the
match.
<a name="smallassertions"></a></P>
<br><b>
Simple assertions
@ -2990,19 +2992,22 @@ match does not always guarantee that a match must be at this starting point.
<P>
Note that (*COMMIT) at the start of a pattern is not the same as an anchor,
unless PCRE's start-of-match optimizations are turned off, as shown in this
<b>pcretest</b> example:
output from <b>pcretest</b>:
<pre>
re&#62; /(*COMMIT)abc/
data&#62; xyzabc
0: abc
xyzabc\Y
data&#62; xyzabc\Y
No match
</pre>
PCRE knows that any match must start with "a", so the optimization skips along
the subject to "a" before running the first match attempt, which succeeds. When
the optimization is disabled by the \Y escape in the second subject, the match
starts at "x" and so the (*COMMIT) causes it to fail without trying any other
starting points.
For this pattern, PCRE knows that any match must start with "a", so the
optimization skips along the subject to "a" before applying the pattern to the
first set of data. The match attempt then succeeds. In the second set of data,
the escape sequence \Y is interpreted by the <b>pcretest</b> program. It causes
the PCRE_NO_START_OPTIMIZE option to be set when <b>pcre_exec()</b> is called.
This disables the optimization that skips along to the first character. The
pattern is now applied starting at "x", and so the (*COMMIT) causes the match
to fail without trying any other starting points.
<pre>
(*PRUNE) or (*PRUNE:NAME)
</pre>
@ -3221,9 +3226,9 @@ Cambridge CB2 3QH, England.
</P>
<br><a name="SEC30" href="#TOC1">REVISION</a><br>
<P>
Last updated: 03 December 2013
Last updated: 08 January 2014
<br>
Copyright &copy; 1997-2013 University of Cambridge.
Copyright &copy; 1997-2014 University of Cambridge.
<br>
<p>
Return to the <a href="index.html">PCRE index page</a>.