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

[cd.barth at t-online.de]

Thomas, I would use validating semantic predicate 

readNchars
: NUM 
  (b+=CHAR)+ {$b.size()<=Integer.parseInt($NUM.text)}?
;

The idea is from Ter's book The Definitive ANTLR Reference (ANTLR v3)

Gruß Claus-Dieter


-----Ursprüngliche Nachricht-----
Von: Juancarlo Añez [mailto:apalala at gmail.com] 
Gesendet: Donnerstag, 1. November 2012 02:20
An: Thomas Ruschival
Cc: antlr-interest at antlr.org
Betreff: Re: [antlr-interest] how to skip/read next n Characters (n is read form input)

Thomas,

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.

Cheers,

-- 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*