diff options
Diffstat (limited to 'doc/html/pcrecompat.html')
| -rw-r--r-- | doc/html/pcrecompat.html | 50 |
1 files changed, 22 insertions, 28 deletions
diff --git a/doc/html/pcrecompat.html b/doc/html/pcrecompat.html index 0d4e1df..697cb13 100644 --- a/doc/html/pcrecompat.html +++ b/doc/html/pcrecompat.html @@ -17,8 +17,9 @@ DIFFERENCES BETWEEN PCRE AND PERL </b><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. +regular expressions. The differences described here are mainly with respect to +Perl 5.8, though PCRE version 7.0 contains some features that are expected to +be in the forthcoming Perl 5.10. </P> <P> 1. PCRE has only a subset of Perl's UTF-8 and Unicode support. Details of what @@ -76,20 +77,28 @@ following examples: The \Q...\E sequence is recognized both inside and outside character classes. </P> <P> -8. Fairly obviously, PCRE does not support the (?{code}) and (?p{code}) -constructions. However, there is 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. See the +8. Fairly obviously, PCRE does not support the (?{code}) and (??{code}) +constructions. However, there is support for recursive patterns. This is not +available in Perl 5.8, but will be in Perl 5.10. Also, the PCRE "callout" +feature allows an external function to be called during pattern matching. See +the <a href="pcrecallout.html"><b>pcrecallout</b></a> documentation for details. </P> <P> -9. There are some differences that are concerned with the settings of captured +9. Subpatterns that are called recursively or as "subroutines" are always +treated as atomic groups in PCRE. This is like Python, but unlike Perl. +</P> +<P> +10. 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> -10. PCRE provides some extensions to the Perl regular expression facilities: +11. PCRE provides some extensions to the Perl regular expression facilities. +Perl 5.10 will include new features that are not in earlier versions, some of +which (such as named parentheses) have been in PCRE for some time. This list is +with respect to Perl 5.10: <br> <br> (a) Although lookbehind assertions must match fixed length strings, each @@ -119,36 +128,21 @@ only at the first matching position in the subject string. options for <b>pcre_exec()</b> have no Perl equivalents. <br> <br> -(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.) -<br> -<br> -(h) PCRE supports named capturing substrings, using the Python syntax. -<br> -<br> -(i) PCRE supports the possessive quantifier "++" syntax, taken from Sun's Java -package. -<br> -<br> -(j) The (R) condition, for testing recursion, is a PCRE extension. -<br> -<br> -(k) The callout facility is PCRE-specific. +(g) The callout facility is PCRE-specific. <br> <br> -(l) The partial matching facility is PCRE-specific. +(h) The partial matching facility is PCRE-specific. <br> <br> -(m) Patterns compiled by PCRE can be saved and re-used at a later time, even on +(i) Patterns compiled by PCRE can be saved and re-used at a later time, even on different hosts that have the other endianness. <br> <br> -(n) The alternative matching function (<b>pcre_dfa_exec()</b>) matches in a +(j) The alternative matching function (<b>pcre_dfa_exec()</b>) matches in a different way and is not Perl-compatible. </P> <P> -Last updated: 06 June 2006 +Last updated: 28 November 2006 <br> Copyright © 1997-2006 University of Cambridge. <p> |