what 262,715 regex questions on stack overflow haven't answered (part 2)
the html question, the regex that passes and fails on the same input, and other things you may find surprising
ian erik varatalu
phd student at taltech, working on automata theory, algorithms, fast search engines and solvers.
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what 262,715 regex questions on stack overflow haven't answered
complement, intersection, and why the most common regex workarounds are hundreds of times slower than they need to be
finding all regex matches has always been O(n²). even in the engines built to prevent it
every regex engine that promises linear time breaks that promise the moment you ask for all matches. the problem has been there since the 70s, hiding in the iteration loop.