Re: [Boost-users] [mpl] Inheriting from each type in a sequence

From: Gottlob Frege (gottlobfrege_at_[hidden])
Date: 2007-03-27 23:01:16

On 3/27/07, Scott Meyers <usenet_at_[hidden]> wrote:
> Given some base class,
>
>    class Base { virtual ~Base(){} };
>
> I want to be able to implement this:
>
>    template<typename Seq>
>    const Base& createObject()
>    {
>      // return an object that inherits from Base and every type in Seq
>    }
>
> The problem is how to create the type of object I want.
>
> Thanks,
>
> Scott

I'm probably won't use the correct mpl-isms, but something like

template <typename Seq>
struct inherit_all
{
   struct type
   :
   public virtual first<Seq>::type,
   public virtual inherit_all<tail<Seq>::type>::type
   {
   };
};

assuming first<> and tail<> exist or are easily implementable.

Then

template <typename Seq>
struct Base_and_Seq
   :
   public virtual Base,
   public virtual inherit_all<Seq>::type
{
};

>    template<typename Seq>
>    const Base& createObject()
>    {
>      // return an object that inherits from Base and every type in Seq
         return new Base_and_Seq<Seq>();
>    }

Does any of that work, or at least head in the right direction?  Or am
I just recreating what inherit_linearly, etc already does?

Tony