Subject: Re: [xsl] parsing parens in the park From: "Dimitre Novatchev" <dnovatchev@xxxxxxxxx> Date: Sun, 28 Sep 2008 14:24:05 -0700 |
> Actually if all you need to do is test to see if they match or not, > you can do easier things. In an iterative language, > while (string has parens) { > remove all occurrences of "()" > if there were none, signal an error > } > if you get here without error, it's OK. It would be good to know that this is an O(N^2) algorithm. -- Cheers, Dimitre Novatchev --------------------------------------- Truly great madness cannot be achieved without significant intelligence. --------------------------------------- To invent, you need a good imagination and a pile of junk ------------------------------------- Never fight an inanimate object ------------------------------------- You've achieved success in your field when you don't know whether what you're doing is work or play On Sun, Sep 28, 2008 at 2:15 PM, Liam Quin <liam@xxxxxx> wrote: > On Sun, Sep 28, 2008 at 09:15:45PM +0100, David Carlisle wrote: >> You can not match nested brackets with regular expressions. (That's more >> or less the defining restriction which is implied by "regular"). > > Agreed... > >> To match brackets you need to use, in addition to regular expressions, a >> language that can either count or (equivalently) has a unbounded stack. >> (Eg recursive function calls). > > Actually if all you need to do is test to see if they match or not, > you can do easier things. In an iterative language, > while (string has parens) { > remove all occurrences of "()" > if there were none, signal an error > } > if you get here without error, it's OK. > > The XSLT implementaion of this would be recursive though. > > Perl regexps can mach parens, and there's an example in the > "perldoc perlre" or, "man perlre" documentation. > > Liam > > -- > Liam Quin, W3C XML Activity Lead, http://www.w3.org/People/Quin/ > http://www.holoweb.net/~liam/ * http://www.fromoldbooks.org/
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