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revision 91 by nigel, Sat Feb 24 21:41:34 2007 UTC revision 93 by nigel, Sat Feb 24 21:41:42 2007 UTC
# Line 6  PCRE - Perl-compatible regular expressio Line 6  PCRE - Perl-compatible regular expressio
6  .sp  .sp
7  The PCRE library is a set of functions that implement regular expression  The PCRE library is a set of functions that implement regular expression
8  pattern matching using the same syntax and semantics as Perl, with just a few  pattern matching using the same syntax and semantics as Perl, with just a few
9  differences. The current implementation of PCRE (release 6.x) corresponds  differences. (Certain features that appeared in Python and PCRE before they
10  approximately with Perl 5.8, including support for UTF-8 encoded strings and  appeared in Perl are also available using the Python syntax.)
 Unicode general category properties. However, this support has to be explicitly  
 enabled; it is not the default.  
11  .P  .P
12  In addition to the Perl-compatible matching function, PCRE also contains an  The current implementation of PCRE (release 7.x) corresponds approximately with
13    Perl 5.10, including support for UTF-8 encoded strings and Unicode general
14    category properties. However, UTF-8 and Unicode support has to be explicitly
15    enabled; it is not the default. The Unicode tables correspond to Unicode
16    release 5.0.0.
17    .P
18    In addition to the Perl-compatible matching function, PCRE contains an
19  alternative matching function that matches the same compiled patterns in a  alternative matching function that matches the same compiled patterns in a
20  different way. In certain circumstances, the alternative function has some  different way. In certain circumstances, the alternative function has some
21  advantages. For a discussion of the two matching algorithms, see the  advantages. For a discussion of the two matching algorithms, see the
# Line 114  distribution and the Line 118  distribution and the
118  \fBpcrebuild\fP  \fBpcrebuild\fP
119  .\"  .\"
120  documentation for details). In these cases the limit is substantially larger.  documentation for details). In these cases the limit is substantially larger.
121  However, the speed of execution will be slower.  However, the speed of execution is slower.
122  .P  .P
123  All values in repeating quantifiers must be less than 65536. The maximum  All values in repeating quantifiers must be less than 65536. The maximum
124  compiled length of subpattern with an explicit repeat count is 30000 bytes. The  compiled length of subpattern with an explicit repeat count is 30000 bytes. The
125  maximum number of capturing subpatterns is 65535.  maximum number of capturing subpatterns is 65535.
126  .P  .P
127  There is no limit to the number of non-capturing subpatterns, but the maximum  There is no limit to the number of parenthesized subpatterns, but there can be
128  depth of nesting of all kinds of parenthesized subpattern, including capturing  no more than 65535 capturing subpatterns.
 subpatterns, assertions, and other types of subpattern, is 200.  
129  .P  .P
130  The maximum length of name for a named subpattern is 32, and the maximum number  The maximum length of name for a named subpattern is 32 characters, and the
131  of named subpatterns is 10000.  maximum number of named subpatterns is 10000.
132  .P  .P
133  The maximum length of a subject string is the largest positive number that an  The maximum length of a subject string is the largest positive number that an
134  integer variable can hold. However, when using the traditional matching  integer variable can hold. However, when using the traditional matching
# Line 160  instead of just strings of bytes. Line 163  instead of just strings of bytes.
163  .P  .P
164  If you compile PCRE with UTF-8 support, but do not use it at run time, the  If you compile PCRE with UTF-8 support, but do not use it at run time, the
165  library will be a bit bigger, but the additional run time overhead is limited  library will be a bit bigger, but the additional run time overhead is limited
166  to testing the PCRE_UTF8 flag in several places, so should not be very large.  to testing the PCRE_UTF8 flag occasionally, so should not be very big.
167  .P  .P
168  If PCRE is built with Unicode character property support (which implies UTF-8  If PCRE is built with Unicode character property support (which implies UTF-8
169  support), the escape sequences \ep{..}, \eP{..}, and \eX are supported.  support), the escape sequences \ep{..}, \eP{..}, and \eX are supported.
# Line 232  Philip Hazel Line 235  Philip Hazel
235  .br  .br
236  University Computing Service,  University Computing Service,
237  .br  .br
238  Cambridge CB2 3QG, England.  Cambridge CB2 3QH, England.
239  .P  .P
240  Putting an actual email address here seems to have been a spam magnet, so I've  Putting an actual email address here seems to have been a spam magnet, so I've
241  taken it away. If you want to email me, use my initial and surname, separated  taken it away. If you want to email me, use my initial and surname, separated
242  by a dot, at the domain ucs.cam.ac.uk.  by a dot, at the domain ucs.cam.ac.uk.
243  .sp  .sp
244  .in 0  .in 0
245  Last updated: 05 June 2006  Last updated: 23 November 2006
246  .br  .br
247  Copyright (c) 1997-2006 University of Cambridge.  Copyright (c) 1997-2006 University of Cambridge.
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