Hi, I found both left recursion as well as other aspects of ANTLR quite tricky esp as I had very little experience with ANTRL and grammars in general. There is also no "quick and dirty" way to do it - books on the subject are quite hefty :-( Anyway, I am really looking forward to another ANTLR grammar - perhaps we can merge both at the end and come out with one that works for really all cases.
Kind regards, Bostjan On Fri, 2012-01-13 at 11:10 +0000, Seref Arikan wrote: > Thanks Mikael, > I've also found left recursion to be less of a problem as I focused on > the grammar. The details, and especially the division of tasks between > lexer and parser in Antlr is what is tricky, as you've also pointed > out. > > I decided to keep working on my version without peeking at any other > work, to see what comes out of that (probably lots of things to laugh > at). There is now already an Antlr grammar out there, thanks to > Marand, but I find the idea of having multiple works out there very > exciting. 2012 has certainly started well for the openEHR community! > > Best regards > Seref > > > > 2012/1/13 Mikael Nystr?m <mikael.nystrom at liu.se> > > Hi, > > > > I used the standard approach for rewriting left recursion to > non left recursion described in computer grammar books (and in > Wikipedia http://en.wikipedia.org/wiki/Left_recursion). It > was a quite straight forward translation, but it was necessary > to be careful with all the details. :-) We will share the > grammar when we have cleaned up the file a little more. > > > > Regards, > > Mikael > > > > > > > From: openehr-technical-bounces at openehr.org > [mailto:openehr-technical-bounces at openehr.org] On Behalf Of > Erik Sundvall > Sent: den 5 januari 2012 11:12 > To: For openEHR technical discussions > Subject: Re: Did anybody implement AQL with a LL parser > framework? > > > > > Hi! > > > > > > We implemented an AQL parser using JavaCC. My colleague Mikael > Nystr?m made some transformations to make the published AQL > grammar work in JavaCC. Mikael is on vacation right now, but > I'm sure he does not mind sharing his experiences once he gets > back. > > > > > > I do think it would be interesting to switch to ANTLR sooner > or later in order to share efforts between projects with > different implementation/target-languages and because the > ANTLRWorks environment http://www.antlr.org/works/index.html > looks promising compared to the pretty bad JavaCC-plugin in > e.g. Eclipse. > > > > > > Our parser (and thus also the modified grammar) will soon be > open sourced so you are free to use it. So if you are not in > an extreme hurry I'd suggest using or getting inspiration from > what we have already done. > > > > > > Best regards, > Erik Sundvall > erik.sundvall at liu.se http://www.imt.liu.se/~erisu/ Tel: > +46-13-286733 > > > > > On Wed, Jan 4, 2012 at 16:37, Seref Arikan > <serefarikan at kurumsalteknoloji.com> wrote: > > Greetings, > The AQL grammar from the wiki has direct and indirect left > recursion. Which means without changes in the grammar, LL > parser generators (both JavaCC and Anltr) can't generate > parsers for this grammar. > > I'm curious if anybody has refactored this grammar for LL > parser generators. Shinji? Your latest release includes an AQL > parser does not it? Could you please share your method? I can > always look at the code, but you'd probably save me time :) > > I'm interested in experiences of others too. > > > Kind regards > Seref > > > > > _______________________________________________ > openEHR-technical mailing list > openEHR-technical at openehr.org > http://lists.chime.ucl.ac.uk/mailman/listinfo/openehr-technical > > > > > _______________________________________________ > openEHR-technical mailing list > openEHR-technical at openehr.org > http://lists.chime.ucl.ac.uk/mailman/listinfo/openehr-technical -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.openehr.org/mailman/private/openehr-technical_lists.openehr.org/attachments/20120113/f5601aba/attachment.html> -------------- next part -------------- A non-text attachment was scrubbed... Name: face-sad.png Type: image/png Size: 1057 bytes Desc: not available URL: <http://lists.openehr.org/mailman/private/openehr-technical_lists.openehr.org/attachments/20120113/f5601aba/attachment.png>
