[antlr-interest] How can I avoid "mismatched input" error?

[Indhu Bharathi]

Looks like you are trying to use keyword as identifier. AFAIK, this 
cannot be resolved in the lexer. You have to use predicates in the 
parser rule. Something like this:

rule : keyKEYWORD1 (keyKEYWORD2 enc=Name)? ';' ;

keyKEYWORD1
    :    {input.LT(1).getText().equals("keyword1")}? Name ;

keyKEYWORD2
    :    {input.LT(1).getText().equals("keyword2")}? Name ;


One more problem I see is the production "Name : Letter* ;". Lexer 
production cannot define a zero length string.

Another problem is you are expecting 'keyword1' to be parsed as Name but 
production for Name doesn't allow numbers.

- Indhu

Gabriel Petrovay wrote:
> Hi all,
>
> I have the following grammar file:
>
> //========================================
> grammar k;
> options {
> output=AST;
> }
>
> rule : KEYWORD1 (KEYWORD2 enc=Name)? ';' ;
>
> KEYWORD1 : 'keyword1';
> KEYWORD2 : 'keyword2';
>
> Name : Letter* ;
> fragment Letter : 'a'..'z' | 'A'..'Z' ;
>
> S            :    ('\t' | ' ' | '\n' | '\r')+  { $channel = HIDDEN; } ;
> //========================================
>
>
> The following text is not a valid one.
>
> INPUT:
> =====
> keyword1 keyword2 keyword1 ;
>
> OUTPUT:
> =======
> line 1:18 mismatched input 'keyword1' expecting Name
> <mismatched token: [@4,18:25='keyword1',<4>,1:18], resync=keyword1 
> keyword2 keyword1 ;>
>
>
> How can I make a parser to recognize this input? I want to be able to 
> allow the keywords in the places where any char combination is 
> allowed. How can I make this?
>
> Regards,
> Gabriel
> ------------------------------------------------------------------------
>
>
> List: http://www.antlr.org/mailman/listinfo/antlr-interest
> Unsubscribe: http://www.antlr.org/mailman/options/antlr-interest/your-email-address
>   

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.antlr.org/pipermail/antlr-interest/attachments/20090324/13b82b39/attachment.html