Re: FYI: default %printer/%destructor

[Hans Aberg]

On 19 Nov 2006, at 23:54, Joel E. Denny wrote:

> > On Sun, 19 Nov 2006, Hans Aberg wrote:
> >
> > > > > The %destructor is only needed with output language C.
> > > >
> > > > Currently, it's also useful for C++.
> > >
> > > You mean, of one writes code in the common C/C++ subset. :-)
> >
> > I think you, Akim, and I have all agreed that semantic types  
> > cannot have
> > C++ destructors given Bison's current C++ skeletons.  You need % 
> > destructor
> > instead.  That's what I'm referring to.
>
> I should be more careful.  I'm thinking of when you use %union with  
> the
> C++ skeletons.  I have not tried the #define YYSTYPE approach, but I
> recall someone reporting using C++ destructors then.

The problem with %union is that it implements a 'union', which in C++  
cannot be used with non-PODs, essentially, classes with non-trivial  
(or user-defined) destructors. So, therefore, instead use something  
else, plus a method to select dynamics objects.

> Anyway, my point is that %destructor can be useful with Bison's  
> current
> C++ skeletons.

If one really does not want to use one of the main advantages of C++,  
classes with constructors and destructors. I am not sure why one is  
not using C in such a case. :-)

  Hans Aberg