[antlr-interest] NoSuchElementException

[Justin Murray]

Mike,

Thank you for the suggestion. I think I had tried something similar to
this initially, but this also gives me problems. Here is the new
grammar:

----

grammar Test;

// Parser rules
preprocess
	:	line* EOF
	;

line
	:	PP_directive_
	|	SOURCE_LINE_
	;

// Lexer rules

PP_directive_
	:	'#define'
	;
            
NEWLINE_
	:	'\u000D'? '\u000A'
	|	'\u0085'
	|	'\u2028'
	|	'\u2029'
	;
	
SOURCE_LINE_
	:	.* (EOF | NEWLINE_)
	;

----

This one does not crash, but does give me the following error:

error(201): AerobasicPreprocessor.g:27:4: The following alternatives can
never be matched: 1

Line 27 corresponds to the SOURCE_LINE_ rule. This error doesn't really
make any sense to me. If I remove the EOF from the SOURCE_LINE_ rule,
the grammar builds successfully. However, this doesn't give me what I
need, which is the possibility of a line at the end of a file, without a
newline. Any other ideas?

Thanks,

- Justin

-----Original Message-----
From: Mike Lischke [mailto:mike at lischke-online.de] 
Sent: Thursday, September 06, 2012 10:11 AM
To: Justin Murray
Cc: antlr-interest at antlr.org
Subject: Re: [antlr-interest] NoSuchElementException


Justin,

your grammar came over in an ugly format...


Try something like this for lines instead:

SOURCE_LINE_: .* (NEWLINE_ | EOF);

Then your preprocess rule could go like this:

preprocess:
	line* EOF
;


ANTLR is clever enough to exclude the token after the Kleene operator
from what the dot matches, which is very convenient.



> grammar Test;
> 
> 
> 
> options
> 
> {
> 
>                language=C;
> 
> }
> 
> 
> 
> 
> 
> // Parser rules
> 
> preprocess
> 
>                :               (line? NEWLINE_)* line? EOF
> 
>                ;
> 
> 
> 
> line
> 
>                :               PP_directive_
> 
>                |              SOURCE_LINE_
> 
>                ;
> 
> 
> 
> // Lexer rules
> 
> 
> 
> PP_directive_
> 
>                :               '#define'
> 
>                ;
> 
> 
> 
> NEWLINE_
> 
>                :               '\u000D'? '\u000A'
> 
>                |              '\u0085'
> 
>                |              '\u2028'
> 
>                |              '\u2029'
> 
>                ;
> 
> 
> 
> SOURCE_LINE_
> 
>                :               ~NEWLINE_+
> 
>                ;
> 
> 
> 
> 
> 
> So I have two questions. It seems to me that the tool should never 
> crash, so is this an ANTLR bug? Secondly, there is clearly a problem 
> with what I am trying to do here. Is it not possible to capture 
> everything on a line (that is not a newline) as a token? Does anyone 
> have a workaround?
> 
> 
> 
> Thanks,
> 
> 
> 
> - Justin
> 
> 
> List: http://www.antlr.org/mailman/listinfo/antlr-interest
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Mike
--
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