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[REBOL] Re: Parse versus Regular Expressions

From: greggirwin:mindspring at: 5-Apr-2003 18:15

Hi Joel et al, Sorry I don't have time to think deeply (or dink theeply) about this right now, but it's great topic. << Well, since there is no "pure RE" language, I have to use RE as embedded in *some* programming language. I could have just as well used Python, Ruby, Java, awk, etc... >> Are you sure about AWK? I didn't think it supported backreferences, and a quick check in the Friedl RE book seems to bear that out (though a couple modern AWK's might). OK so taking AWK out isn't that important, or why I'm writing. What seems important to me is that - as you pointed out - RE needs a host language and there are many flavors of RE out there. The biggest differences will be between the NFA and DFA engines (DFA engines not supporting backtracking AFAIK). Now, I'm going to be in way over my head if I continue down this path, but it strikes me that we can probably look at the differences in that context rather than on a case-by-case basis with examples. I.e. come up with a general solution, or model, about how to design PARSE rules for these kinds of grammars/situations. This thread has already provided some good examples. For those with the time and desire, the dragon book has a section on how to construct a DFA from an NFA which might provide some pointers. -- Gregg