[antlr-interest] how to skip/read next n Characters (n is read form input)

Juancarlo Añez apalala at gmail.com
Wed Oct 31 18:19:55 PDT 2012


ANTLR may be overkill or inadequate for what you're doing.

I think you'd be better of with a program with a main loop that dispatches
to different functions based on the escape code. Each function can affect
the input position, or do anything else it pleases. It would be
a handcrafted state machine.

You can do this in Python or any of the friendly languages.


-- Juancarlo

On Wed, Oct 31, 2012 at 12:17 PM, Thomas Ruschival <thomas at ruschival.de>wrote:

> I am a humble EE with little grammar experience, please forgive my
> ignorance and give me a hint how professionals would do the trick.
> I came up with a grammar for detecting commands "escape-sequences" in a
> input text (for a UnifiedPOS printer)
> that reads numbers and boolean argumets for escape sequence commands
> from the input stream.
> I can read numeric arguments and use them as function parameters, which
> function to be called is parsed correctly.
> For instance "ESC|#rF" means "print feed revers # lines"
> The question is how to treat "ESC|#E" which means "send the next #
> bytes untreated to the pinter" in other words:
> How can I use a number N that I detected on the input stream to read
> and consume the next N characters
> 'un-lexed' and 'un-parsed' as string/byte array?
> I was thinking using something like this in a parse action using the
> 'input' member of the parser:
> for (int i=0; i<N; i++){
>         output.append(input.LA(1));
>         input.consume();
> }
> But it doesn't seem very professional to me. Furthermore this gives me
> tokens and not plain bytes....
> Can you give me a hint?
> Thanks in advance
> Thomas
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Juancarlo *Añez*

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