Thank you for your explanation. And your solution works great, too.
Christian
Am 03.11.2011 21:31, schrieb Jim Idle:
> You don't want that anyway as your nodes will not have token start and
> stop information and you might need that.
>
> method_declaration
> : method_header method_body
> ;
>
> method_body
> : (
> ';'!
> | '{'! statement_list? '}'!
> )
> -> ^(METHOD_BODY statement_list?)
> ;
>
> method_header
> : attributes ID etc
>
> ->^(METHOD_HEADER attributes ID )
> ;
>
>
> Jim
>
>> -----Original Message-----
>> From: [email protected] [mailto:antlr-interest-
>> [email protected]] On Behalf Of Christian
>> Sent: Thursday, November 03, 2011 1:01 PM
>> To: [email protected]
>> Subject: [antlr-interest] Check if rule returns empty result
>>
>> Hi at all,
>>
>> I have the following rules:
>>
>> method_declaration
>> : method_header method_body -> ^(METHOD_HEADER method_header)
>> ^(METHOD_BODY method_body)
>> ;
>>
>> method_body:
>> ';'!
>> | '{'! statement_list? '}'!;
>> ;
>>
>> Of course, method_body is executed because it has no question mark.
>> However, introducing rewrite rules and operators cause a problem. By
>> using ^(METHOD_BODY method_body), method_body must return a non-empty
>> value. However, statement_list? is optional and thus may not match at
>> all. In this case, method_body returns nothing anymore and I get an
>> RewriteEmpty exception.
>>
>> How can I solve this problem by only changing rewrite rules?
>>
>> Regards,
>> Christian
>>
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