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

skapp at rochester.rr.com skapp at rochester.rr.com
Tue Dec 16 21:03:40 PST 2003


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/ 




More information about the antlr-interest mailing list