> My question is below:
> I have a grammar:
>
> expr :
> (operand) (OPER operand)*
> ;
> operand :
> ID|INT
> ;
> OPER :
> ('+'|'-'|'*'|'/')
> ;
> INT :
> ('0'..'9')+
> ;
> ID :
> ('a'..'z'|'A'..'Z'|'_')('a'..'z'|'A'..'Z'|'_'|'0'..'9')*
> ;
>
> And for the input "t+1", I have the error:
> line 1:4 mismatched input '+'
>
works for me. no errors reported. using the attached test rig under ANTLR
v3.1, August 12, 2008.
> But when I switch "OPER" to "oper", All work as it should. I don't
> understand Why it's so.
>
> Thank you
Hope this helps.
--
John B. Brodie
//---------------------begin attachment-------------------------
grammar Test;
options {
output = AST;
ASTLabelType = CommonTree;
}
@members {
private static final String [] x = new String[]{
"1+1", "t+1"
};
public static void main(String [] args) {
for( int i = 0; i < x.length; ++i ) {
try {
System.out.println("about to parse:`"+x[i]+"`");
TestLexer lexer = new TestLexer(new ANTLRStringStream(x[i]));
CommonTokenStream tokens = new CommonTokenStream(lexer);
TestParser parser = new TestParser(tokens);
TestParser.expr_return p_result = parser.expr();
CommonTree ast = p_result.tree;
if( ast == null ) {
System.out.println("resultant tree: is NULL");
} else {
System.out.println("resultant tree: " +
ast.toStringTree());
}
System.out.println();
} catch(Exception e) {
e.printStackTrace();
}
}
}
}
expr :
(operand) (OPER operand)*
;
operand :
ID|INT
;
OPER :
('+'|'-'|'*'|'/')
;
INT :
('0'..'9')+
;
ID :
('a'..'z'|'A'..'Z'|'_')('a'..'z'|'A'..'Z'|'_'|'0'..'9')*
;
//---------------------end of attachment------------------------
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