[antlr-interest] Using ANTLR's ~ to do match literals causes "no viable alternative" messages in generated Java but not in ANTLRWorks

[Ron Hunter-Duvar]

Hi Davy,

You don't have a rule for consuming whitespace. Add something like this:

WS :
  WS_CHAR+ {$channel=HIDDEN;}
  ;

fragment WS_CHAR :
  (' '|'\r'|'\t'|'\u000C'|'\n')
  ;

Ron


Davy Landman wrote:
> Hello,
>
> I'm having some problems with my generated java parser/lexer, but I've
> tried to reduce the problem to a small subset.
>
> Let's assume the simple language which has identifiers and numbers.
> And the only rules are, a number contains out of only numbers, and a
> identifier can not contain `'?', ':', ' '` and can not begin with a
> number.
>
> I would create the following ANTLR specification of this language.
>
>     grammar simple;
>
>     prog:	expr* EOF;
>
>     expr
>     	:	ID | INT;
>
>
>     ID  : ~('0'..'9'|SEPERATORS) ~(SEPERATORS)*;
>
>     fragment
>     SEPERATORS
>     	:	' ' | ':' | '?';
>
>     INT :	'0'..'9'+
>         ;
>
> And running this in ANTLRWorks debugging and parsing mode, no errors
> are reported to the console.
>
> But if I than generate the Parser and Lexer and try to consume it in a
> java program as such:
>
>     import org.antlr.runtime.ANTLRStringStream;
>     import org.antlr.runtime.CommonTokenStream;
>     import org.antlr.runtime.RecognitionException;
>
>
>     public class runner {
>
>     	public static void main(String args[])
>     	{
>     		simpleLexer lex = new simpleLexer(new ANTLRStringStream("a33 44"));
>     		CommonTokenStream tokens= new CommonTokenStream(lex);
>     		simpleParser parser = new simpleParser(tokens);
>     		try {
>     			parser.prog();
>     		} catch (RecognitionException e) {
>     			e.printStackTrace();
>     		}
>     	}
>     }
>
> The parser works, and the prog() continues succesfully. But in the
> background the following error message is printed to the console.
>
>     line 1:3 no viable alternative at character ' '
>
> The same exact sequence causes no messages to the ANTLRWorks console,
> so I was wondering, am I abusing the ~ ? Or is there a difference
> between the ANTLRWorks debugger and default java runtime?
>
> So if anybody can help me how to get rid of these messages? Because in
> the original lexer and parser where this question is based, I get a
> nice looking AST but only have messages printed to the eclipse
> console.
>
> Versions used:
> ANTLRWorks 1.3.1
> ANTLR-3.2
> Linux x64
>
> Kind regards,
> Davy Landman
>
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>
>   

-- 
Ron Hunter-Duvar | Software Developer V | 403-272-6580
Oracle Service Engineering
Gulf Canada Square 401 - 9th Avenue S.W., Calgary, AB, Canada T2P 3C5

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