[antlr-interest] Inspecting return values

[Jose Ventura]

Hi Janeen,

For return a value from a rule you can put a variable for the invocation
(Sorry by my english). An example


rule1
    : value=r:rule2 {System.out.println ("Rule "+#r.getText+" return
"+value);
    ;
rule2 returns [String value=""]
     : c:command {value=#c.getText();}
     ;

I think the correct sentence is    "rtnValue=tbs: tableswitch [#toggle]! "


2007/1/23, Johnson, Janeen <JOHNSJA at intelsat.com>:
>
>  All
>
> I'm an antlr newbie using 2.7.7 with Java so forgive me (and enlighten me)
> if this is a stupid question.  I've been working on this specific problem
> for 3 days and am still stuck.  I created the ultra simple sample data and
> tableswitch function below to use as a test-case-only within my larger .g
> file.
>
> I have a function 3-5 levels down in my parse tree that returns a String
> value.  In the generated code, the return value isn't captured.  What have I
> done wrong and how can I correct it?
>
> I've snipped a lot of code away above and below these in the tree so if
> what is needed to help me is not included let me know and I'll send more.
> Thank you.  Janeen
>
>
> ____________________________________________________________________________
> Sample input line returned by the lexer:
>
> table-switch-input ( 101-ANT100 )
>
> ____________________________________________________________________________
> In the parser:
>
> (snipped)
>
> statement   : ((status)
>                   | (tableswitch[#toggle])
> … (snipped)
>                   | (LITRL) )
>                  ;
> status        : ((THE) (ID) (OF) (EXTPINNAME));
> tableswitch : ((TABLETSWITCHINPUT) (LPAREN) (EXTPINNAME) (RPAREN)) ;
> (snipped)
>
>
> ______________________________________________________________________________
> In the ParseTree (.g file):
>
> statement [String toggle]  returns [String rtnValue]
>         {
>           rtnValue = "";
>         } : ((sttus: status [#toggle]! { /*  code snipped */} )
>           | (tbs: tableswitch [#toggle]! { /* I would like to check the
> return value at this level of code */ } )
>           | (LITRL)
>           );
>
> tableswitch [String toggle] returns [String rtnValue]
>         { rtnValue = "";
>           int pinValue = 0;
>           String pinName = "";
>           int rtnInt = 0;
>         } : (TABLETSWITCHINPUT! LPAREN! ttpin:EXTPINNAME! RPAREN!
>                         {
>                   (snipped)
>                           rtnInt = tableSwitchFunc.set_param("TABLE-SWITCH-INPUT",
> pinValue);  /*  Call to outside function that returns the correct value */
>
>                           rtnValue = new Integer(rtnInt).toString();
>                           System.out.println("from tableswitch:
> rtnValue); // Correct value prints here
>                          }
>            );
>
>
> ____________________________________________________________________________
> Q:  Where is the return value stored?  How can I inspect it?  How can I
> also assign it as the return value for "statement"?
>
> Generated code -- call from "statement" to tableswitch:
> (snipped)
>                                 case TABLETSWITCHINPUT:
>                                 {
>                                         {
>                                         tbs = _t==ASTNULL ? null :
> (AST)_t;
>                                         tableswitch(_t,toggle);
>         /*  I thought ANTLR would save the return value here, but it doesn't
> look like it */
>
>                                         _t = _retTree;
>                                         tbs_AST = (AST)returnAST;
>                                         rtnValue = tbs.getText
> ().toString();
>
> System.out.println("from statement:  tableswitch rtnValue = " + rtnValue
> );
>
>                                         }
>                                         break;
>                                 }
>  (snipped)
>                         returnAST = statement_AST;
>                         _retTree = _t;
>                         return rtnValue;
>
> (snipped)
>
> Thank you in advance for any help you can give me.
>
> Janeen
>
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