Inline. Thanks for your reply! On Dec 28, 2011, at 12:20 PM, John Leuner <je...@subvert-the-dominant-paradigm.net> wrote:
> Hi Casey > > In my OMeta implementations I have found that simply recording the > position of the deepest error and then printing out the remaining input > text was sufficient to debug my grammars. This is something I hadn't thought of. It would tell one where the grammar choked. That's interesting. > I think the next step I would take (if that wasn't sufficient) is to > create a test suite that tests each grammar rule independently, > successively building up to the complex input that is failing. I'd been doing this for terminals, but it seems like non-terminals get harder to write as unit tests, parser state and all. I suppose integration tests could work, but it seems the more complex the grammatical structure, the more I experience diminishing returns with tests. I just end up with tests that fail mysteriously which is my original problem. Do you have any examples about? I wonder if maybe there's something essential I'm failing to understand. Maybe looking at your tests might send me along to an a-ha moment. Thanks again! > John > > > On Tue, 2011-12-13 at 23:17 -0800, Casey Ransberger wrote: >> I know this has come up before. Hopefully I'm not about to repeat a lot. >> >> Debugging this stuff just seems really hard. And significantly harder than >> what I've experienced working with e.g. Yacc. >> >> Hypothesis: Yacc had a lot of time to bake before I ever found it. PEGs are >> new, so there's been less overall experience with debugging them. >> >> I've experimented in what little time I can devote with OMeta, PetitParser, >> and Treetop. The debugging experience has been roughly consistent across all >> three. >> >> One particular issue which has bugged me: memoization seems to carry a lot >> of instance-state that's really hard to comprehend when the grammar isn't >> working as I expect. It's just really hard to use that ocean of information >> to figure out what I've done wrong. >> >> Given that with these new parsing technologies, we're pretty lucky to see >> "parse error" as an error message, I can't help but think that it's worth >> studying debugging strategies. Heh. :D I'm really not complaining, I'm just >> pointing it out. >> >> Has anyone here found any technique(s) which makes debugging a grammar >> written for a PEG/packrat less of a pain in the butt? >> >> I'd be really interested in hearing about it. >> >> >> >> _______________________________________________ >> fonc mailing list >> fonc@vpri.org >> http://vpri.org/mailman/listinfo/fonc > > > > _______________________________________________ > fonc mailing list > fonc@vpri.org > http://vpri.org/mailman/listinfo/fonc _______________________________________________ fonc mailing list fonc@vpri.org http://vpri.org/mailman/listinfo/fonc
