[antlr-interest] "start of line" issue in lexer

[Micheal J]

Look at the csharp_v1 example in 'examples/csharp/csharp_v1'. The lexer
deals with preprocessor directives that must similarly be the first
non-whitespace token on a line.
 
In general, the examples provide a rich source of ideas.
 
 
Micheal
 

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The best way to contact me is via the list/forum. My time is very limited. 

-----Original Message-----
From: antlr-interest-bounces at antlr.org
[mailto:antlr-interest-bounces at antlr.org] On Behalf Of Michiel Vermandel
Sent: 21 June 2006 15:39
To: antlr-interest at antlr.org
Subject: [antlr-interest] "start of line" issue in lexer



Hi, 

I need a lexer rule to skip comment in a part of code-text. 

The rule should only be used if "rem" is at the start of the line or only
preceeded by whitespaces and/or tabs. 

so given this part of code: 


rem setting a to 5 
set a=5; 
rem setting lvrem to a 
set lvrem = a; 


the first and the third line should be concidered as comment. 
the fourth line should be left alone. 

building a rule for the case in line 3 is quite easy because I can search
for new line characters, but for the very first line that is not possible
since there are no preceeding new line characters. 

how do I have to handle this? 

Thanks a lott! 


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