template<class T>
class allocator
{
    ...
    template<class Other>
    struct rebind { typedef allocator<Other> other; };
};

template<class T, class Alloc = std::allocator<T> >
class vector { ... };

template<class T>
class allocator { ... };

template<class T, template<class> class Alloc = std::allocator>
class vector { ... };

template<unsigned int PoolSize>
struct pool
{
    template<class T>
    struct allocator
    {
        T pool[PoolSize];

        ...
    };
};

template<class T, template<class> class Alloc>
class vector { ... };

typedef vector<int, pool<1>::allocator> int_vector;

std::vector<T, my_allocator<T,Arg2> > v1;

std::vector<T, my_allocator_wrapper<Arg2>::template type > v2;