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What sort of Regex are they using? The garden variety can be compiled to DFAs (O(n)) which a modern computer should have no issues handling. Further optimizations



Here is a good example:

http://git.savannah.gnu.org/cgit/emacs.git/tree/lisp/emacs-l...

DFAs for regular expressions use exponential memory for regular expression size (also exponential time to compile them to DFAs). Try that for the regular expressions in the link above. There is no way to make regular expressions fast.


I believe Emacs has its own regular expression syntax that doesn't correspond exactly to either POSIX regexes, PCRE, or any other common regex variant. (Presumably because none of them existed yet when Emacs implemented regexes?)




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