Is there anyone here with sufficient computer science skillz to answer the question whether it is possible to write a program which will take an arbitrary regexp and contruct another which will act as it's negation against all possible input strings?
I would imagine you'd have to restrict the definition of "regular expression" to something a little less rich than the full perl set (isn't there a compsci definition?).
Presumably if regexps form a turing complete language then the answer is no, because this sounds awfully like such a program would violate the the Halting Problem (but maybe not - I haven't thought about it in detail).
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