Jasmine
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Jan 19, 2001, 2:46 PM
Post #1 of 1
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How do I find matching/nesting anything?
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(From the Perl FAQ)
How do I find matching/nesting anything?
This isn't something that can be done in one regular expression, no matter how complicated. To find something between two single characters, a pattern like /x([^x]*)x/ will get the intervening bits in $1. For multiple ones, then something more like /alpha(.*?)omega/ would be needed. But none of these deals with nested patterns, nor can they. For that you'll have to write a parser.
If you are serious about writing a parser, there are a number of modules or oddities that will make your life a lot easier. There is the CPAN module Parse::RecDescent, the standard module Text::Balanced, the byacc program, and Mark-Jason Dominus's excellent py tool at http://www.plover.com/~mjd/perl/py/.
One simple destructive, inside-out approach that you might try is to pull out the smallest nesting parts one at a time: while (s//BEGIN((?:(?!BEGIN)(?!END).)*)END/gs) {
# do something with $1
} |
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