[antlr-interest] Re: Positioning input stream (was EOL sequence)

[lgc at mail1.jpl.nasa.gov]

Steve--

I had a thought.  Have you set k to 2 or higher in your lexer?  If it's 1, that would cause problems.

--Loring



--- In antlr-interest at yahoogroups.com, skapp at r... wrote:
> I have worked out enough details with the EOL sequences to 
> understand where my PostScript parser is failing. PostScript parsers 
> have to be able to handle the following four example sequences 
> identically:
> 
> currentfile read 3
> currentfile read<CR>3
> currentfile read<LF>3
> currentfile read<CR><LF>3
> 
> where the "currentfile read" operator sequence instructs the 
> PostScript interpreter to read one byte from the input stream.
> 
> There is no issue with the first three examples. The input stream 
> point just past the EOL byte once the "read" operator has been 
> recognized. Then the read operator simply has to pull one byte from 
> the input stream (a FileInputStream in this case).
> 
> However, in the fourth case, the input stream points to the <LF> 
> character when the "read" operator has been recognized. The 
> PostScript spec states that "Any of the three forms of EOL ... is 
> treated as a single white-space character."
> 
> How do I handle this? What can or should I do in the lexer versus in 
> the parser?
> 
> Regards,
> 
>    Steve


 

Yahoo! Groups Links

To visit your group on the web, go to:
 http://groups.yahoo.com/group/antlr-interest/

To unsubscribe from this group, send an email to:
 antlr-interest-unsubscribe at yahoogroups.com

Your use of Yahoo! Groups is subject to:
 http://docs.yahoo.com/info/terms/