[antlr-interest] WG: RE: RE: rules with parameters are not equivalent to ruleswithout parameters

[Kristian Marinkovic]

Hi Remco and John,

thank you very much!!!

a=a_sub did the trick! :)

g,
kris


                                                                           
             "Remco van                                                    
             Engelen"                                                      
             <Remco.van.Engele                                          An 
             n at asml.com>                "Kristian Marinkovic"              
                                        <kristian.marinkovic at porsche.co.at 
             10.10.2006 14:07           >                                  
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                                                                     Thema 
                                        RE: RE: [antlr-interest] rules     
                                        with parameters are not equivalent 
                                        to ruleswithout parameters         
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           




Hi Kristian,

Sorry, my bad ;-) It should be:

( a=a_sub | b=b_sub) COL c SEMIC {//do sth};


With the notation a:a_sub you assign to a the AST that is returned by the
rule a_sub, not the return value. If a_sub were a lexer rule, a:a_sub would
return the token of a_sub into a, and you could use the getText() method to
access the token text (this is also a typical idiom to use; but it only
work for lexer rules, not parser rules).


Regards


Remco,
From: Kristian Marinkovic [mailto:kristian.marinkovic at porsche.co.at]
Sent: Tue 10/10/2006 2:05 PM
To: Remco van Engelen
Subject: RE: RE: [antlr-interest] rules with parameters are not equivalent
to ruleswithout parameters



Hi Remco,

the problem is indeed, that ANTLR can't 'see' the rule.
I already tried to change the rules as you suggested
but a and b are not assigned with the desired value.
ANTLR just reports: warning:Rule 'a_sub' returns a value

generated code:
String a = null;
String b = null;
...
switch ( LA(1)) {
   case LITERAL_AAA:
  {
   a_sub();
   break;
                  }



             "Remco van
             Engelen"
             <Remco.van.Engele                                          An
             n at asml.com>                "Kristian Marinkovic"
                                        <kristian.marinkovic at porsche.co.at
             10.10.2006 13:53           >
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                                                                     Thema
                                        RE: [antlr-interest] rules with
                                        parameters are not equivalent to
                                        ruleswithout parameters










It seems to me you are calling the subrules directly from within action
code blocks, where ANTLR cannot 'see' them (ANTLR does not look into your
action code). You should be fine if you rewrite it as follows:

body
{
      String a = null;
      String b = null;
}
:
( a:a_sub | b: b_sub) COL c SEMIC {//do sth};

Regards,

Remco,

From: antlr-interest-bounces at antlr.org on behalf of Kristian Marinkovic
Sent: Tue 10/10/2006 1:43 PM
To: antlr-interest at antlr.org
Subject: [antlr-interest] rules with parameters are not equivalent to
ruleswithout parameters




Hello,

i'm trying to understand why antlr is generating different code for rules
with parameters and rules without parameters.

I assumed that the 2 examples below are equivalent?!

example without parameter:

a : "AAA";
b : "BBB";
c : "CCC";

startRule : (body)*;

body : (a | b) COL c SEMIC {//do sth};


example with parameter:

startRule : (body)*;

body
{
      String a = null;
      String b = null;
}
:
( {a = a_sub();} | {b = b_sub();} ) COL c SEMIC {//do sth};;

a_sub returns [String a] : a { a = "AAA"; //alt. get it from token};
b_sub returns [String b] : b { b =" BBB"; //alt. get it from token};

Is there another way i can solve this? Because the parser with the
parameter is not deterministic! I'm using Antlr 2.7.5

g,
kris





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