[antlr-interest] a crazy problem cost me almost two days ---how can i get the return value from antlr?

[Jim Idle]

On Mon, 2008-11-24 at 05:59 -0800, Su Zhang wrote:
> thanks,i see that, yet there is not any value in this String, i
> checked my grammar part and did not find any errors or problem? would
> you take a look at my grammar and see whether there is a problem in
> the project?
> the grammar is here:
>  
> num    returns [String t]
>         :n = Num  {$t = $n.getText();}|b64=Base64Block{$t=
> $b64.getText();}|ident=Id{$t=$ident.getText();}


This has already been pointed out once, but don't use getText(). You
want to use:

$n.text $b64.text $ident.text


>         ;
> base1   returns[String input] 


input is already in use as an object name within ANTLR, you need to use
a different name.

Then if your grammar is called myGrammar, you invoke it as:


myGrammar parser = new myGrammar(tokens);  // Set up your parser

// Next, your num rule will either return String (as you only have one return element) or the type num_return:
//

// Either...
//
num_return psrReturn = parser.num();
System.out.println("Return was " + psrReturn.t);

// Or if it just returns string:
//
String psrReturn = parser.num();
System.out.println("Return was " + psrReturn);

If you are not getting back a string value, then there is an error in
your grammar actions. 

I suggest that you buy a copy of the book or at least scan all the
available example grammars and contributed grammars.

Jim
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