[antlr-interest] How to use an optional rule attribute in anaction?

[troy runkel]

In this particular case it looks like I can assign the ';' token to a
variable and that variable will be initialized to NULL.  Then I can
just check the 'semi' variable in the action.  The following seems to
be working for me.  Thanks

create_procedure :
    'CREATE' ('PROC' | 'PROCEDURE') procedure_name ( semi=';' num=number )?
    {
        if (semi != NULL)
        {
            someFunction($num.text);
        }
    }

Troy Runkel

On 6/26/07, Jim Idle <jimi at temporal-wave.com> wrote:
> Hmm - I'll look at that, I think it probably SHOULD be initialized to
> NULL, but perhaps I don't hae the label list or something (doubtful
> though).
>
> For now you could do this:
>
> create_procedure
> @declarations
> {
>         ANTLR3_BOOLEAN haveNumber;
> }
> @init
> {
>         haveNumber = ANTLR3_FALSE;
> }
> :
>           'CREATE' ('PROC' | 'PROCEDURE') procedure_name
>         ( ';'number { $haveNumber = ANTLR3_TRUE; } )?
>           {
>               if ($haveNumber)
>                   {
>                       printf("Found number '%s'\n", $n.text->chars);
>                       someFunction($n.text);
>                   }
>           }
>
>
> But, now that I look at what you are doing, can't you do this:
>
>     (';' n=number { someFunction($n.text->chars); })?
>
> Jim
>
> > -----Original Message-----
> > From: antlr-interest-bounces at antlr.org [mailto:antlr-interest-
> > bounces at antlr.org] On Behalf Of troy runkel
> > Sent: Tuesday, June 26, 2007 12:18 PM
> > To: antlr-interest at antlr.org; trunkel at gmail.com
> > Subject: Re: [antlr-interest] How to use an optional rule attribute in
> > anaction?
> >
> > > > -----Original Message-----
> > > > From: antlr-interest-bounces at antlr.org [mailto:antlr-interest-
> > > > bounces at antlr.org] On Behalf Of troy runkel
> > > > Sent: Tuesday, June 26, 2007 11:51 AM
> > > > To: ANTLR mail-list
> > > > Subject: [antlr-interest] How to use an optional rule attribute in
> > an
> > > > action?
> > > >
> > > > Greetings,
> > > >
> > > > I'm using ANTLR v3 with the C-target and have a situation like the
> > > > following.  I have an optional rule called number and I want to
> > access
> > > > the text attribute of that rule if and only if the rule was
> > applied.
> > > > Using the C-target, $number is uninitialized if the rule wasn't
> > > > applied.  Is there a way, in the action, to determine if
> > $number.text
> > > > is valid?
> > > >
> > >
> > > create_procedure :
> > >          'CREATE' ('PROC' | 'PROCEDURE') procedure_name ( ';'
> > n=number
> > > )?
> > >          {
> > >              if ($n != NULL)
> > >                  {
> > >                      printf("Found number '%s'\n", $n.text->chars);
> > >                  someFunction($n.text);
> > >                  }
> > >          }
> > >
> > > Makes most sense to me.
> > >
> > > Jim
> >
> > I tried that, but using the C-target the n variable will be
> > uninitialized if the number rule was not applied.  Therefore, n will
> > not be NULL but will instead be some random value.  In the Visual
> > Studio 2005 debugger n is initialized to 0xcccccccc but that's not
> > very helpful.  :-)
> >
> > Troy Runkel
>