[antlr-interest] "Comments" token from source to the target language

Austin Hastings Austin_Hastings at Yahoo.com
Mon Nov 12 16:38:25 PST 2007


Mateus,

I'd recommend that you not hide the comment tokens. Instead, recognize 
them, translate them, and then include them in your AST. You should do 
an early-stage AST rewrite to get the comments out of the way - attach 
them to the nodes instead. Then you can go back to AST rewriting for the 
language itself.

=Austin


Mateus Baur da Silva wrote:
> Hi Ter,
>
> I understand that parser will ignore the tokens if I set the token to 
> be sent to the parser thru the hidden channel ($channel=HIDDEN;).
>
> By reading your message (and your book), I know I can check the hidden 
> channel for the comments token inside my actions. However, I don't 
> know how to do that. Is there some sample implementing this behavior?
>
> If not, could you (or someone else) let me know how I should implement 
> that inside my actions?
>
> Thanks and Regards,
> Mateus
>
>
> On Nov 12, 2007 8:03 PM, Terence Parr < parrt at cs.usfca.edu 
> <mailto:parrt at cs.usfca.edu>> wrote:
>
>
>     On Nov 12, 2007, at 11:38 AM, Mateus Baur da Silva wrote:
>
>     > Hi Guys,
>     >
>     > As I mentioned in some my other email, I doing a translator from a
>     > Pascal subset to java. Currently, I'm ignoring the "comments" by
>     > using skip() on the lexer rule that defines the "comments".
>     >
>     > However, I would like to translate the comments from Pascal to Java
>     > code as well. I was wondering if I could do that by using the
>     > HIDDEN_CHANNEL or some other feature to properly translate the
>     > comments. Does someone have any clue on how to do that?
>     >
>
>     Yep, use the hidden token thing.  Your actions then ask for the
>     hidden tokens between real tokens.  Parser ignores them.
>
>     Ter
>
>
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