Re: How to ignore a token if it doesn't fit in with a rule?

[uclacasey]

Thanks for the response.  I already am using an exclusive start condition to
pass the comment to Bison.  Could you explain what you mean?  I don't see
how this can solve the problem of ignoring a token if it doesn't fit into a
rule.

John P. Hartmann wrote:
> 
> That is probably much easier to handle by exclusive start conditions
> in the scanner.
> 
> On 23 July 2011 02:40, uclacasey <address@hidden> wrote:
>>
>> I'm writing a program that handles comments as well as a few other
>> things. If
>> a comment is in a specific place, then my program does something.
>>
>> Flex passes a token upon finding a comment, and Bison then looks to see
>> if
>> that token fits into a particular rule. If it does, then it takes an
>> action
>> associated with that rule.
>>
>> Here's the thing: the input I'm receiving might actually have comments in
>> the wrong places. In this case, I just want to ignore the comment rather
>> than flagging an error.
>>
>> My question:
>> How can I use a token if it fits into a rule, but ignore it if it
>> doesn't?
>> Can I make a token "optional"?
>>
>> (Note: The only way I can think of of doing this right now is scattering
>> the
>> comment token in every possible place in every possible rule. There MUST
>> be
>> a better solution than this. Maybe some rule involving the root?)
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