[Opencxx-users] Re: [opencxx] Let's break OpenC++ up

[Stefan R. <sr...@ma...>]

On Mon, Apr 14, 2003 at 04:32:57AM -0700, James Michael DuPont wrote:
> --- Stefan Reuther <sr...@ma...> wrote:
> > Another possibility would be to put that knowledge into the
> > Walker interface. Here, we have such a thing for
> > PtreeDeclaration. Depending upon whether a PtreeDeclaration is a
> > class declaration ("class foo;"), a name declaration ("int x;")
> > or a function implementation ("void x() { }"), it nicely
> > dissects the tree node and calls different functions. "Class"
> > and "ClassWalker" already seem to do some other parts of this.
> 
> The walker has only one problem.
> It does not only walk, but also has to interpret things.
> It has to know how to extract the data out of the parser
> 
> How do you propose to hide the details of the parser from the walker?

I would not hide the details.

Someone has to know about the Ptree structure, right? My point
was making Walker the one who knows it.

Like this:
   // users can override this method
   virtual Ptree* TranslateNamespaceCooked(Ptree* keyword,
                                           Ptree* name,
                                           Ptree* content);
   // this method is called by PtreeNamespace::Translate
   virtual Ptree* TranslateNamespaceRaw(PtreeNamespace* p) {
       return TranslateNamespaceCooked(p->Car()    /* "namespace" */,
                                       p->Second() /* the namespace name */,
                                       p->Third()  /* the contents */);
   }

I'm not exactly sure, but maybe that's not too flexible (one
can't inspect a given Ptree except by making a custom Walker and
calling it).

The other solution,
  class PtreeNamespace : public Ptree {
    public:
      Ptree* GetKeyword() { return Car(); }
      Ptree* GetName() { return Second(); }
      Ptree* GetContent() { return Third(); }
  };
puts that knowledge into the Ptree itself, which I like, but I
feel there are performance problems for things like "GetName" in
a PtreeDeclarator (it has to skip over a number of "*", "&",
"class::*" and cv-qualifiers to find the name or sub-declarator).
But maybe that's not at all a problem (caching?).

Using handle classes (Grzegorz' way) would definitely work nice,
but it's a lot of work to implement it.


  Stefan