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

[John P. Hartmann]

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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