/[pcre]/code/trunk/doc/pcrecompat.3
ViewVC logotype

Diff of /code/trunk/doc/pcrecompat.3

Parent Directory Parent Directory | Revision Log Revision Log | View Patch Patch

revision 635 by ph10, Sat Jul 23 16:19:50 2011 UTC revision 654 by ph10, Tue Aug 2 11:00:40 2011 UTC
# Line 20  in the main Line 20  in the main
20  .\"  .\"
21  page.  page.
22  .P  .P
23  2. PCRE does not allow repeat quantifiers on assertions. Perl permits them, but  2. PCRE allows repeat quantifiers only on parenthesized assertions, but they do
24  they do not mean what you might think. For example, (?!a){3} does not assert  not mean what you might think. For example, (?!a){3} does not assert that the
25  that the next three characters are not "a". It just asserts that the next  next three characters are not "a". It just asserts that the next character is
26  character is not "a" three times.  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 \eb, but
28    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
31  counted, but their entries in the offsets vector are never set. Perl sets its  counted, but their entries in the offsets vector are never set. Perl sets its
# Line 37  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 53  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 110  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.
# Line 171  Cambridge CB2 3QH, England. Line 173  Cambridge CB2 3QH, England.
173  .rs  .rs
174  .sp  .sp
175  .nf  .nf
176  Last updated: 23 July 2011  Last updated: 24 July 2011
177  Copyright (c) 1997-2011 University of Cambridge.  Copyright (c) 1997-2011 University of Cambridge.
178  .fi  .fi

Legend:
Removed from v.635  
changed lines
  Added in v.654

  ViewVC Help
Powered by ViewVC 1.1.5