[antlr-interest] Question on aborting rule based on pattern

[Stanimir Stamenkov]

/Stanimir Stamenkov/:

> You need to put 'aaa' and 'ccc' productions as alternatives to some 
> rule, like:
[...]

Or may be I haven't understood you goal correctly and you might need 
a syntactic predicate [1] in the 'ddd' rule:

aaa : "AAAA" SPACE bbb ccc ;

bbb : ( ddd )+ ;

ddd : ("XXX") => ccc
     | ha:ATOM ":" SPACE eee SPACE ; // Rule 1

eee : hva:ATOM (":" hvap:ATOM)* ;

ccc : "XXX" ":" SPACE ((cccentry)+ ; // Rule 2

Or if the 'ATOM' lexer rule tests for literals it would match the 
"XXX" literal and I think no predicate is necessary:

ddd : ccc
     | ha:ATOM ":" SPACE eee SPACE ; // Rule 1

But I see ambiguity arises and finally you may need to change the 
'aaa' and 'bbb' rules:

aaa : "AAAA" SPACE bbb ;

bbb : ( ddd )+ ccc ;

ddd : ha:ATOM ":" SPACE eee SPACE ; // Rule 1

eee : hva:ATOM (":" hvap:ATOM)* ;

ccc : "XXX" ":" SPACE ((cccentry)+ ; // Rule 2

The above given the 'ATOM' lexer rule tests for literals.

[1] http://www.antlr.org/doc/metalang.html#SyntacticPredicates

-- 
Stanimir