[antlr-interest] observation on example in "An Introduction To
ANTLR"
Paul Tasillo
ptasillo at us.ibm.com
Mon Jul 17 13:49:09 PDT 2006
I was following the examples in Terrance Parr's document "An Introduction
To ANTLR" (http://www.cs.usfca.edu/~parrt/course/652/lectures/antlr.html)
and couldn't get the tool to recognize end of line characters such that
the expr() method returned. After reading some of Ashley Mill's ANTLR
documents, I found the following change the seemed to solve the problem:
The original lexer has:
class ExprLexer extends Lexer;
options {
k=2; // needed for newline junk
charVocabulary='\u0000'..'\u007F'; // allow ascii
}
LPAREN: '(' ;
RPAREN: ')' ;
PLUS : '+' ;
MINUS : '-' ;
STAR : '*' ;
INT : ('0'..'9')+ ;
WS : ( ' '
| '\r' '\n'
| '\n'
| '\t'
)
{$setType(Token.SKIP);}
;
I found this change was helpful:
class ExprLexer extends Lexer;
options {
k=2;
charVocabulary='\u0000'..'\u007F'; //allow ascii
}
LPAREN : '(';
RPAREN : ')';
PLUS : '+';
MINUS : '-';
STAR : '*';
INT : ('0'..'9')+ ;
NEWLINE :('\r''\n'
|'\n'
|'\r'
)
{newline();};
WS : (' '|'\t')
{$setType(Token.SKIP);};
I was running on Windows XP Pro with Java 1.4.2 and the latest Beta of
Antlr 3.02b I think.
-Paul
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