Re: [boost] Is type list defined in boost

17 Jul 2007

      On 7/17/07, David Abrahams <dave@boost-consulting.com> wrote:
...
on Tue Jul 17 2007, "Peng Yu" <pengyu.ut-AT-gmail.com> wrote:
...
On 7/16/07, Mathias Gaunard <mathias.gaunard@etu.u-bordeaux1.fr> wrote:
...
Peng Yu wrote:
...
I've seen typelist somewhere. I'm wondering if it is defined in boost?
Boost has better than that, it has the Boost Meta-Programming Library
(MPL) that contains various data structures and algorithms around types.
Hi,
I saw list in mpl. But I'm not familiar with it yet. Would you please
show me how to do the same thing in mpl as that in my original
email?
typedef boost::mpl::list<Rect_, Square_, Triangle_, RightTriangle_> Shapes_;
Hi,

I actually meant to define a visitor class for those shapes like the
following. Is there anything similar to type_list::head and
type_list::tail in mpl::list?

In the following code, I need to "using" the visit function from the
visitor<typename TL::tail, Base>. But there is not visit function in
visitor<list_end, Base>. Do you know how make the using statement
conditional on the base visitor class?

Thanks,
Peng

class A;
class B;

typedef type_list<A, type_list<B> > AB;

class base {
 public :
   virtual ~base() {}
   virtual void accept(base& b) = 0 ;
};

template <typename TL, typename Base>
class visitor : public visitor<typename TL::tail, Base> {
 public :
   virtual ~visitor() { }
   virtual void visit(typename TL::head &) {
      std::cout << __PRETTY_FUNCTION__ << std::endl;
   }
   using visitor<typename TL::tail, Base>::visit;
//    no visit() function defined for visitor<list_end, Base>
// is there any way to make the above using statement conditional?
// (if the base class is visitor<list_end, Base>, not to use this statement.)
};

template <typename Base>
class visitor<list_end, Base> : public Base {
 public :
   virtual ~visitor() { }

};