Непонятна Неизвесто wrote: > Hello, > > I would like to make my own translator but has faced with one problem - > lexer's rules overlapping. I want to have two lexer rules like this: > > ID 'a'..'z'+; > ENG 'a'..'z'; > > and > > INT '0'..'9'+; > DIG '0'..'9; ... > word: > 'inputword' ':' (ID|INT) 'in' '['axsis']' ';' > ; //^ it is important that here was placed only one > character > > and then find input errors (like this 123 in [1,2,3]) by the tree grammar
The problem with your thinking is that the lexing (dividing into tokens) all happens before the parser gets to see anything. Thus the lexer has no knowledge of the parse context (because there is no parse context yet), so when it sees abcdef It doesn't know whether it should be 6 ENG tokens or one ID token. If you have a situation where you want to ensure a token is only one character long, you can (using predicates), but if you want to recognise 123 as an INT in one context and three DIGs in another, you have a problem. One solution would be to make INT and ID into parser rules, int and id, formed as DIG+ and ENG+ respectively. That would leave a messy tree, though. -- Sam Barnett-Cormack 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 [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/il-antlr-interest?hl=en -~----------~----~----~----~------~----~------~--~---
