[antlr-interest] return value during backtracking

[Terence Parr]

Use {{...}} to force action evaluation during backtrack
ter
On Nov 13, 2009, at 1:42 AM, Philippe Faes wrote:

> Hi everybody,
>
> I can't figure out how to set a return value during backtracking.
> While backtracking, I'd like to do a semantic check on a return  
> value of an underlying rule, but the return values are not set  
> during backtracking.
>
> Example:
>
> some_rule
>   : designator operand {someCheck($designator.text)}? // this will  
> never work
>   ;
> designator returns [Node node, String text]
>   : identifier { $node = $identifier.node; $text=$identifier.text; }
>   | operator_symbol {$node = $operator_symbol.node; $text= 
> $operator_symbol.text; }
>   ;
>
> Any ideas?
>
> Thanks
>
> Philippe
>
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