[antlr-interest] How to apply predicates

[Horst Dehmer]

Hello!

I have the following rather simple grammar (which is probable not  
context-free).
The input 'X0110000063{...' is (naturally) matched as a LITERAL  
'X0110000063', whereas I need it to be X01 followed by the literal/ 
entity_id '10000063'. I am sure this can be achieved by using a  
(syntactic/semantic) predicate, but I just don't know how.

Any help is highly appreciated.

Thanks,
Horst


transaction: X01 (update_type)+ EOF;
update_type: entity_id '{' (basic_update)+ '}';
basic_update: '{' field ('|' field)* '}';
field: (description)?;
entity_id returns [String value]: LITERAL { $value = $LITERAL.text; };
description returns [String value]: LITERAL { $value = $LITERAL.text; };

fragment ESCAPE_CHARACTER: '`';
fragment SPECIAL_CHARACTER: ESCAPE_CHARACTER | '|' | '{' | '}';
ESCAPE: ESCAPE_CHARACTER SPECIAL_CHARACTER;

X01: 'X01';

LITERAL
   : ( ESCAPE |
       '\u0009'..'\u000A' |
       '\u000D' |
       '\u0020'..'\u005F' |
       '\u0061'..'\u007A' |
       '\u007E'
     )+
   ;

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