Avoid backtracking like the plague if you need performance. But if you are careful in the order of your alts and use it on just a few decisions/rules, then it might not be so bad (but remember that your error messages will be weak).
If k=1 on a decision then ANTLR will work that out so you don't need to specify but if you want to avoid ANTLR following every possible alt then you can use k=1 on a particular rule or sub rule to avoid ambiguity errors. Basically if you know that a decision will be correct at k=1 even though ANTLR can see ambiguities, then tell it so. Before 3.4 this would still give a warning unless you added a 1 token predicate, but I believe that Ter changed this for 3.4 so that I could remove a lot of those predicates from my own T-SQL grammar. Jim > -----Original Message----- > From: antlr-interest-boun...@antlr.org [mailto:antlr-interest- > boun...@antlr.org] On Behalf Of Ruslan Zasukhin > Sent: Wednesday, October 12, 2011 11:05 AM > To: antlr-interest@antlr.org > Subject: [antlr-interest] Advice on best practice? > > Hi All, Terrence, Jim, > > I have review FAQs, other docs and list ... > But sop far cannot find isolated advices/tips of kind > > > * Tend develop grammar as k=1 > AVOID to use k=*, because this is slower ... > > OR reverse > > * No problems to use k=* > Always prefer to use k=* and do not worry ... Speed will be fine.. > > OR > > * always tend to (not)? Use backtrack option. > and if you use it then use memoize also ... > > > In the ANTLR3/Examples/C I see options as > > > ==================== > grammar C; > > options > { > backtrack = true; > memoize = true; > k = 2; > language = C; > } > ==================== > > > But what is official point of view at current state ? > > > > -- > Best regards, > > Ruslan Zasukhin > VP Engineering and New Technology > Paradigma Software, Inc > > Valentina - Joining Worlds of Information > http://www.paradigmasoft.com > > [I feel the need: the need for speed] > > > > List: http://www.antlr.org/mailman/listinfo/antlr-interest > Unsubscribe: http://www.antlr.org/mailman/options/antlr-interest/your- > email-address List: http://www.antlr.org/mailman/listinfo/antlr-interest Unsubscribe: http://www.antlr.org/mailman/options/antlr-interest/your-email-address -- You received this message because you are subscribed to the Google Groups "il-antlr-interest" group. To post to this group, send email to il-antlr-inter...@googlegroups.com. To unsubscribe from this group, send email to il-antlr-interest+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/il-antlr-interest?hl=en.
