[antlr-interest] Matching the * character

[Loring Craymer]

This looks ok, except for the (STAR | QUESTION*)? idiom (equivalent to (STAR | QUESTION+ | | ).  Try either changing QUESTION* to QUESTION+ or remove the terminal ?.  I would have thought that ANTLR would issue a warning about the two empty alts; maybe it did and you missed it.

--Loring

----- Original Message ----
From: Steve O'Hara <sohara at pivotal-solutions.co.uk>
To: antlr-interest at antlr.org
Sent: Thursday, March 27, 2008 4:27:33 PM
Subject: [antlr-interest] Matching the * character

  
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I'mnew to Antlr so forgive me if this is a stupid question...
I'm trying to match a database search criteria that looks like the following;
   
 'some
text'*, *'more criteria' & 'more criteria'*
 
My grammar is;
   
 expression
    
: subExpression (WS? (COMMA | AMPERSAND) WS? subExpression)*
    
;
   
 subExpression
    
: WS? (Identifier | subExpressionText) WS?
    
;
   
 subExpressionText
    
:  (STAR | QUESTION*)? QuotedString  (STAR | QUESTION*)? WS?
    
;
   
 Letter
: 'a'..'z' | 'A'..'Z' | '_' | '\u0080'..'\ufffe' ;
 Digit
: '0'..'9' ;
 Identifier
: Letter (Letter | Digit)* ;
 QuotedString
:'\'' (~'\'')* '\'' ;
 WS
: (' ' | '\t' | '\n' | '\r')+ ;
   
 COMMA
: ',' ;
 AMPERSAND
: '&' ;
 QUESTION
: '?' ;
 STAR
: '*' ;
 
The parser finds the first quoted string (some text) but fails after that witha NoViableAltException. If I change the * to ? it works fine. I'm waiting fordelivery of the reference manual so maybe I'm breaking some sort of golden rulehere, but any help would be greatly appreciated.

Steve
   
 SteveO'Hara
Pivotal Solutions 

 ( +44 (0)7802 484227
    +44 (0)208 660 7288 (Fax)
*  sohara at pivotal-solutions.co.uk
 



 
 






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