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Editorial Team
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Asked: 2026-06-02T20:45:10+00:00

I have to create a Lexer which will accept for example an integer only

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I have to create a Lexer which will accept for example an integer only if it has a maximum of 8 digits. Is here an alternative to do it rather than just writing it like this? 

INTEGER : (DIG | DIG DIG | DIG DIG DIG | ...)
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1 Answer

  1. Editorial Team

    This can be done using a Gated Semantic Predicates like this:

    INTEGER
@init{int n = 1;}
  :  ({n <= 8}?=> DIGIT {n++;})+
  ;

fragment DIGIT : '0'..'9';

    Details about this kind of predicate, see: What is a 'semantic predicate' in ANTLR?

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