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diff --git a/external-libs/pcre/doc/html/pcrecompat.html b/external-libs/pcre/doc/html/pcrecompat.html new file mode 100644 index 00000000..1ec22038 --- /dev/null +++ b/external-libs/pcre/doc/html/pcrecompat.html @@ -0,0 +1,136 @@ +<html> +<head> +<title>pcrecompat specification</title> +</head> +<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> +This HTML document has been generated automatically from the original man page. +If there is any nonsense in it, please consult the man page, in case the +conversion went wrong.<br> +<ul> +<li><a name="TOC1" href="#SEC1">DIFFERENCES FROM PERL</a> +</ul> +<br><a name="SEC1" href="#TOC1">DIFFERENCES FROM PERL</a><br> +<P> +This document describes the differences in the ways that PCRE and Perl handle +regular expressions. The differences described here are with respect to Perl +5.8. +</P> +<P> +1. PCRE does not have full UTF-8 support. Details of what it does have are +given in the +<a href="pcre.html#utf8support">section on UTF-8 support</a> +in the main +<a href="pcre.html"><b>pcre</b></a> +page. +</P> +<P> +2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl permits +them, but they do not mean what you might think. For example, (?!a){3} does +not assert that the next three characters are not "a". It just asserts that the +next character is not "a" three times. +</P> +<P> +3. Capturing subpatterns that occur inside negative lookahead assertions are +counted, but their entries in the offsets vector are never set. Perl sets its +numerical variables from any such patterns that are matched before the +assertion fails to match something (thereby succeeding), but only if the +negative lookahead assertion contains just one branch. +</P> +<P> +4. Though binary zero characters are supported in the subject string, they are +not allowed in a pattern string because it is passed as a normal C string, +terminated by zero. The escape sequence "\0" can be used in the pattern to +represent a binary zero. +</P> +<P> +5. The following Perl escape sequences are not supported: \l, \u, \L, +\U, \P, \p, \N, and \X. In fact these are implemented by Perl's general +string-handling and are not part of its pattern matching engine. If any of +these are encountered by PCRE, an error is generated. +</P> +<P> +6. PCRE does support the \Q...\E escape for quoting substrings. Characters in +between are treated as literals. This is slightly different from Perl in that $ +and @ are also handled as literals inside the quotes. In Perl, they cause +variable interpolation (but of course PCRE does not have variables). Note the +following examples: +</P> +<P> +<pre> + Pattern PCRE matches Perl matches +</PRE> +</P> +<P> +<pre> + \Qabc$xyz\E abc$xyz abc followed by the + contents of $xyz + \Qabc\$xyz\E abc\$xyz abc\$xyz + \Qabc\E\$\Qxyz\E abc$xyz abc$xyz +</PRE> +</P> +<P> +The \Q...\E sequence is recognized both inside and outside character classes. +</P> +<P> +7. Fairly obviously, PCRE does not support the (?{code}) and (?p{code}) +constructions. However, there is some experimental support for recursive +patterns using the non-Perl items (?R), (?number) and (?P>name). Also, the PCRE +"callout" feature allows an external function to be called during pattern +matching. +</P> +<P> +8. There are some differences that are concerned with the settings of captured +strings when part of a pattern is repeated. For example, matching "aba" against +the pattern /^(a(b)?)+$/ in Perl leaves $2 unset, but in PCRE it is set to "b". +</P> +<P> +9. PCRE provides some extensions to the Perl regular expression facilities: +</P> +<P> +(a) Although lookbehind assertions must match fixed length strings, each +alternative branch of a lookbehind assertion can match a different length of +string. Perl requires them all to have the same length. +</P> +<P> +(b) If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the $ +meta-character matches only at the very end of the string. +</P> +<P> +© If PCRE_EXTRA is set, a backslash followed by a letter with no special +meaning is faulted. +</P> +<P> +(d) If PCRE_UNGREEDY is set, the greediness of the repetition quantifiers is +inverted, that is, by default they are not greedy, but if followed by a +question mark they are. +</P> +<P> +(e) PCRE_ANCHORED can be used to force a pattern to be tried only at the first +matching position in the subject string. +</P> +<P> +(f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAPTURE +options for <b>pcre_exec()</b> have no Perl equivalents. +</P> +<P> +(g) The (?R), (?number), and (?P>name) constructs allows for recursive pattern +matching (Perl can do this using the (?p{code}) construct, which PCRE cannot +support.) +</P> +<P> +(h) PCRE supports named capturing substrings, using the Python syntax. +</P> +<P> +(i) PCRE supports the possessive quantifier "++" syntax, taken from Sun's Java +package. +</P> +<P> +(j) The (R) condition, for testing recursion, is a PCRE extension. +</P> +<P> +(k) The callout facility is PCRE-specific. +</P> +<P> +Last updated: 09 December 2003 +<br> +Copyright © 1997-2003 University of Cambridge. |