[antlr-interest] Syntactic Predicate does not work but Backtracking does

[Terence Parr]

  those rules are totally different.  One has an alternative and the  
other does not.
Ter
On Mar 1, 2008, at 1:00 AM, Alexander Gängel wrote:

> sorry I send a wrong copy of the first version it should be:
>
> expression_comma options
>     :(
>     (expression COMMA)=>expression COMMA expression_comma - 
> >expression expression_comma
>     |expression->expression
>     )
>     ;
>
> Alexander Gängel schrieb:
>>
>> I have a rule in my grammar like this:
>> expression_comma options
>>     :(
>>     (expression COMMA)=>expression (COMMA expression_comma)? - 
>> >expression expression_comma?
>>     |expression->expression
>>     )
>>     ;
>>
>> my some Input like expression, expression does not work even when  
>> both parts left and rigth of the comma are expressions.
>>
>> if I use this rule with backtracking it works.
>> oclExpression_comma options {backtrack=true;}
>>     :
>>     oclExpression (COMMA oclExpression_comma)? ->oclExpression  
>> oclExpression_comma?
>>     ;
>>
>> Am I wrong or should both work all right?
>> Alexander