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kazinator
on Feb 13, 2015
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A regular expression to check for prime numbers
POSIX regular expressions (file glob patterns, BRE's and ERE's) have more features than regexes in old CS papers, but they are still regular: they compile to automata with no backtracking.
schoen
on Feb 13, 2015
[–]
The ERE described in egrep(1) has backreferences which can match non-regular languages. Are you thinking of some other notion of ERE?
btilly
on Feb 13, 2015
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parent
[–]
He is thinking of what POSIX specified, which does not have backreferences. See
http://www.regular-expressions.info/posix.html
for details.
schoen
on Feb 13, 2015
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root
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[–]
Aha, I didn't know about the difference between POSIX ERE and GNU ERE. Thank you!
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