Variants

[Hans Aberg]

On 27 May 2009, at 20:52, Akim Demaille wrote:

> You will be able to do that in Bison 2.6.  A preview is available at
>
> http://www.lrde.epita.fr/~akim/download/bison-2.4.266-4ff3b.tar.bz2


You might add a reference count GC to your variants. The action syntax  
would be
  $$ = $k;
if one wants to hand over a reference. If one wants to have an  
independent copy, then add extra functions:
  $$ = $k.clone();
or
  $$ = $k; $$.detach();

Since you have a stack of fixed size objects, the implementation of  
such a GC might be simplified: the parser stack just has a state value  
and a pointer to the semantic value. The latter is implemented as a  
sequence of linked objects, with reference count. This could be made  
into a tracing GC, if not because of the destructors that must be  
called.

  Hans Aberg