newbie metaprogramming question

From: Istvan Buki (istvan.buki_at_[hidden])
Date: 2003-08-17 11:55:25

Hello Boost experts,

I'm starting learning about template metaprogramming and I discovered that 
Boost provide several libraries in that area.
I tried to see if those libraries could be used for a piece of code I have in 
my mind but I have a hard time figuring out how to start with it.
I don't know if it is because I try to apply metaprogramming techniques in a 
use case where they doesn't fit or because of my lack of experience with 
these tools. I'm posting my use case here to get some help and advice about 
it.

In a library I provide two classes:

1) An abstract base class (let's call it Base) from which user will derive 
their own classes.
2) A manager class responsible for manipulating instances of  classes derived 
from Base.

The user, in his application, create an an arbitrary number of classes derived 
from Base. Let's call them A, B and C for example.
He create a typelist containing all those classes and passes it as a parameter 
to the manager class:

typedef boost::mpl::list< A, B, C > my_types ;
typedef Manager< my_types> my_manager ;

When an instance of my_manager is created I would like to automatically create 
one instance of each type present in the typelist and these instances should 
be stored in a container where I could access them later. Something like the 
following:

template < class Typelist >
class Manager
{
public:
        Manager( void ) ;

        // .....

private:
        std::vector< Base * > container_ ;

        // ....
} ;

template < class Typelist >
Manager< Typelist >::Manager( void )
{
        // This is not C++, it is pseudo-code that shows what I would
        // like to achieve.

        FOR EACH Typelist item i
        DO
                Base *b = new Typelist[i]
                container_.push_back( b ) ;
        END
}

So, at compile-time, some code should be generated to do what I wrote in 
pseudo-code in the constructor of Manager.
Does this make any sense ? And if it is, could someone help me transform 
transform the pseudo-code in the constructor of manager to real code ?

Thanks for any help you could provide,
Istvan