| 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 \b, 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 |
| 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 |
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