Greetings!
(very sorry, I have broken the mail list threading. I deleted the
original message and then now decided to reply. Sorry. I could not find
a way to reply from the archive. Sorry)
Original message:
> Here's a problem I am having and can't figure out: I am trying to parse a
> hexadecimal string and zeroes
>
> I build a very small example to highlight what the problem is.
>
> Suppose an elemental log file for your check account. It just has credits and
> debits. Debits are identified by
> a prelude of '0001' and credits by '0002' Then comes the amount, up to $
> 65535.
>
>
> We make a modest start with a $100 credit and a $50 debit. So our log is
> '0001006400020030'
__________________________________________________^^^___________________________________^^^^
$48 debit right? anyway, does not really matter i think.
>
> But the input window shows 0001064000103, some zeroes are missing - which of
> course is not what we want.
____________________________________^^^^ huh? 0002 right?
I assume by `input window` you mean some interaction dialog from within
ANTLRWorks? if so, maybe the
problem is with ANTLRWorks? and not the generated parser/lexer?
>
> If we try with a $ 4369 deposit, the log is 0001111100020030.
>
> Now the input window shows 0001111100010030. The credit is not altered, the
> debit is still losing zeroes.
_____________________________________^^^^ huh? ... and where is the loss of
zeroes?
if this is really what you are seeing, I suggest that there is some issue
outside of the ANTLR generated parser
and lexer, because the Tool generated code does not display any "input window"
dialog.
>
> My question is ¿Why do the zeroes get this "special treatment"? ¿How can I
> avoid it or work around it?
>
>
> I would really appreciate either an explanation or some pointers to learn
> what is wrong here.
....remainder snipped....
Have you tried running your generated code from the command line? As indicated
above I think your problem is
outside of any ANTLR generated parser/lexer.
To prove that, please find attached a grammar that just works when Tool'd,
compiled, and executed from the
command line. The linux command line I used is: java org.antlr.Tool Test.g ;
javac *.java ; java TestParser
Hope this helps....
-jbb
grammar Test;
options {
output = AST;
ASTLabelType = CommonTree;
}
@members {
private static final String [] x = new String[] {
"0001006400020030"
};
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.start_return p_result = parser.start();
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();
}
}
}
}
start : (credit | debit)+ EOF!;
credit : '0001'^ HEX ;
debit : '0002'^ HEX ;
fragment HEXIT : ('0'..'9') | ('a'..'f') | ('A'..'F') ;
HEX : HEXIT HEXIT HEXIT HEXIT ;
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