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revision 654 by ph10, Tue Aug 2 11:00:40 2011 UTC revision 788 by ph10, Tue Dec 6 15:38:01 2011 UTC
# Line 10  versions 5.10 and above. Line 10  versions 5.10 and above.
10  .P  .P
11  1. PCRE has only a subset of Perl's UTF-8 and Unicode support. Details of what  1. PCRE has only a subset of Perl's UTF-8 and Unicode support. Details of what
12  it does have are given in the  it does have are given in the
 .\" HTML <a href="pcre.html#utf8support">  
 .\" </a>  
 section on UTF-8 support  
 .\"  
 in the main  
13  .\" HREF  .\" HREF
14  \fBpcre\fP  \fBpcreunicode\fP
15  .\"  .\"
16  page.  page.
17  .P  .P
# Line 43  represent a binary zero. Line 38  represent a binary zero.
38  own, matching a non-newline character, is supported.) In fact these are  own, matching a non-newline character, is supported.) In fact these are
39  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
40  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
41  generated.  generated by default. However, if the PCRE_JAVASCRIPT_COMPAT option is set,
42    \eU and \eu are interpreted as JavaScript interprets them.
43  .P  .P
44  6. The Perl escape sequences \ep, \eP, and \eX are supported only if PCRE is  6. The Perl escape sequences \ep, \eP, and \eX are supported only if PCRE is
45  built with Unicode character property support. The properties that can be  built with Unicode character property support. The properties that can be
# Line 84  the Line 80  the
80  .\"  .\"
81  documentation for details.  documentation for details.
82  .P  .P
83  10. Subpatterns that are called recursively or as "subroutines" are always  10. Subpatterns that are called as subroutines (whether or not recursively) are
84  treated as atomic groups in PCRE. This is like Python, but unlike Perl. There  always treated as atomic groups in PCRE. This is like Python, but unlike Perl.
85  is a discussion of an example that explains this in more detail in the  Captured values that are set outside a subroutine call can be reference from
86    inside in PCRE, but not in Perl. There is a discussion that explains these
87    differences in more detail in the
88  .\" HTML <a href="pcrepattern.html#recursiondifference">  .\" HTML <a href="pcrepattern.html#recursiondifference">
89  .\" </a>  .\" </a>
90  section on recursion differences from Perl  section on recursion differences from Perl
# Line 97  in the Line 95  in the
95  .\"  .\"
96  page.  page.
97  .P  .P
98  11. There are some differences that are concerned with the settings of captured  11. If (*THEN) is present in a group that is called as a subroutine, its action
99    is limited to that group, even if the group does not contain any | characters.
100    .P
101    12. There are some differences that are concerned with the settings of captured
102  strings when part of a pattern is repeated. For example, matching "aba" against  strings when part of a pattern is repeated. For example, matching "aba" against
103  the pattern /^(a(b)?)+$/ in Perl leaves $2 unset, but in PCRE it is set to "b".  the pattern /^(a(b)?)+$/ in Perl leaves $2 unset, but in PCRE it is set to "b".
104  .P  .P
105  12. PCRE's handling of duplicate subpattern numbers and duplicate subpattern  13. PCRE's handling of duplicate subpattern numbers and duplicate subpattern
106  names is not as general as Perl's. This is a consequence of the fact the PCRE  names is not as general as Perl's. This is a consequence of the fact the PCRE
107  works internally just with numbers, using an external table to translate  works internally just with numbers, using an external table to translate
108  between numbers and names. In particular, a pattern such as (?|(?<a>A)|(?<b)B),  between numbers and names. In particular, a pattern such as (?|(?<a>A)|(?<b)B),
# Line 111  would not be possible to distinguish whi Line 112  would not be possible to distinguish whi
112  names map to capturing subpattern number 1. To avoid this confusing situation,  names map to capturing subpattern number 1. To avoid this confusing situation,
113  an error is given at compile time.  an error is given at compile time.
114  .P  .P
115  13. Perl recognizes comments in some places that PCRE does not, for example,  14. Perl recognizes comments in some places that PCRE does not, for example,
116  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,
117  Perl allows whitespace between ( and ? but PCRE never does, even if the  Perl allows whitespace between ( and ? but PCRE never does, even if the
118  PCRE_EXTENDED option is set.  PCRE_EXTENDED option is set.
119  .P  .P
120  14. PCRE provides some extensions to the Perl regular expression facilities.  15. PCRE provides some extensions to the Perl regular expression facilities.
121  Perl 5.10 includes new features that are not in earlier versions of Perl, some  Perl 5.10 includes new features that are not in earlier versions of Perl, some
122  of which (such as named parentheses) have been in PCRE for some time. This list  of which (such as named parentheses) have been in PCRE for some time. This list
123  is with respect to Perl 5.10:  is with respect to Perl 5.10:
# Line 150  by the PCRE_BSR_ANYCRLF option. Line 151  by the PCRE_BSR_ANYCRLF option.
151  (i) The partial matching facility is PCRE-specific.  (i) The partial matching facility is PCRE-specific.
152  .sp  .sp
153  (j) Patterns compiled by PCRE can be saved and re-used at a later time, even on  (j) Patterns compiled by PCRE can be saved and re-used at a later time, even on
154  different hosts that have the other endianness.  different hosts that have the other endianness. However, this does not apply to
155    optimized data created by the just-in-time compiler.
156  .sp  .sp
157  (k) The alternative matching function (\fBpcre_dfa_exec()\fP) matches in a  (k) The alternative matching function (\fBpcre_dfa_exec()\fP) matches in a
158  different way and is not Perl-compatible.  different way and is not Perl-compatible.
# Line 173  Cambridge CB2 3QH, England. Line 175  Cambridge CB2 3QH, England.
175  .rs  .rs
176  .sp  .sp
177  .nf  .nf
178  Last updated: 24 July 2011  Last updated: 14 November 2011
179  Copyright (c) 1997-2011 University of Cambridge.  Copyright (c) 1997-2011 University of Cambridge.
180  .fi  .fi

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