/[pcre]/code/trunk/doc/pcrecompat.3
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revision 637 by ph10, Sun Jul 24 17:44:12 2011 UTC revision 654 by ph10, Tue Aug 2 11:00:40 2011 UTC
# Line 23  page. Line 23  page.
23  2. PCRE allows repeat quantifiers only on parenthesized assertions, but they do  2. PCRE allows repeat quantifiers only on parenthesized assertions, but they do
24  not mean what you might think. For example, (?!a){3} does not assert that the  not mean what you might think. For example, (?!a){3} does not assert that the
25  next three characters are not "a". It just asserts that the next character is  next three characters are not "a". It just asserts that the next character is
26  not "a" three times (in principle: PCRE optimizes this to run the assertion  not "a" three times (in principle: PCRE optimizes this to run the assertion
27  just once). Perl allows repeat quantifiers on other assertions such as \b, but  just once). Perl allows repeat quantifiers on other assertions such as \eb, but
28  these do not seem to have any use.  these do not seem to have any use.
29  .P  .P
30  3. Capturing subpatterns that occur inside negative lookahead assertions are  3. Capturing subpatterns that occur inside negative lookahead assertions are
# Line 39  terminated by zero. The escape sequence Line 39  terminated by zero. The escape sequence
39  represent a binary zero.  represent a binary zero.
40  .P  .P
41  5. The following Perl escape sequences are not supported: \el, \eu, \eL,  5. The following Perl escape sequences are not supported: \el, \eu, \eL,
42  \eU, and \eN when followed by a character name or Unicode value. (\eN on its  \eU, and \eN when followed by a character name or Unicode value. (\eN on its
43  own, matching a non-newline character, is supported.) In fact these are  own, matching a non-newline character, is supported.) In fact these are
44  implemented by Perl's general string-handling and are not part of its pattern  implemented by Perl's general string-handling and are not part of its pattern
45  matching engine. If any of these are encountered by PCRE, an error is  matching engine. If any of these are encountered by PCRE, an error is
# Line 55  the internal representation of Unicode c Line 55  the internal representation of Unicode c
55  implement the somewhat messy concept of surrogates."  implement the somewhat messy concept of surrogates."
56  .P  .P
57  7. PCRE implements a simpler version of \eX than Perl, which changed to make  7. PCRE implements a simpler version of \eX than Perl, which changed to make
58  \eX match what Unicode calls an "extended grapheme cluster". This is more  \eX match what Unicode calls an "extended grapheme cluster". This is more
59  complicated than an extended Unicode sequence, which is what PCRE matches.  complicated than an extended Unicode sequence, which is what PCRE matches.
60  .P  .P
61  8. PCRE does support the \eQ...\eE escape for quoting substrings. Characters in  8. PCRE does support the \eQ...\eE escape for quoting substrings. Characters in
# Line 112  names map to capturing subpattern number Line 112  names map to capturing subpattern number
112  an error is given at compile time.  an error is given at compile time.
113  .P  .P
114  13. Perl recognizes comments in some places that PCRE does not, for example,  13. Perl recognizes comments in some places that PCRE does not, for example,
115  between the ( and ? at the start of a subpattern. If the /x modifier is set,  between the ( and ? at the start of a subpattern. If the /x modifier is set,
116  Perl allows whitespace between ( and ? but PCRE never does, even if the  Perl allows whitespace between ( and ? but PCRE never does, even if the
117  PCRE_EXTENDED option is set.  PCRE_EXTENDED option is set.
118  .P  .P
119  14. PCRE provides some extensions to the Perl regular expression facilities.  14. PCRE provides some extensions to the Perl regular expression facilities.
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