You can still define the match in the superclass -- just use an interface like Edgar mentioned and I demonstrated in the "clarification" note I sent.
I think the big value here would be that it forces every place that uses the token types to use the enum names (as there are no integer values). I think that would help debugging enormously (rather than seeing '4' as the value in the variables window, you'd see 'IDENT'). -- Scott ---------------------------------------- Scott Stanchfield http://javadude.com On Wed, May 19, 2010 at 2:34 PM, Terence Parr <pa...@cs.usfca.edu> wrote: > > On May 18, 2010, at 2:58 PM, Scott Stanchfield wrote: > >> There are several advantages to enums: >> * there is a discrete set of values that can be used (no accidental >> 42's passed in when 42 isn't a token type) >> * the enum value can carry extra information >> * the enum values can override methods differently > > These are all excellent advantages. I believe that these mostly apply when > you're writing code, not generating. Just like the compiler generates > integers underneath, if antlr is generating integers, it's probably okay. > >> OH - one of the things that's clouding this is that you really don't >> need the numeric type identifers anymore. You can just have >> >> public enum TokenType { >> IDENT, INT ...; >> } >> >> then in your match method: >> >> void match(TokenType type) { >> if (LA(1).getType() == type) { >> ... >> } >> } > > The only problem is that match() lives up in the superclass in the library > but the generated parser needs to define the enum. > > I also have the problem that I need to merge token types from multiple > grammars for grammar imports. This gets more competition with enum types > without inheritance. > >> >> And you can use the types in a switch statement: >> >> switch(type) { >> case INT: >> case IDENT: >> ... >> } >> >> No more magic numbers! Woohoo! > > ANTLR already uses the labels when possible such as INT. If you use a literal > in your grammar such as ';' in don't label it in the lexer, than I had no > choice but to generate the integer token type or a weird label like TOKEN34. > > Ter > > 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.
