Traversing a C++ tuple in an order defined at runtime

Question

It's possible to iterate over a boost or std tuple, but can I iterate in an order determined at runtime, while still retaining type information?

Suppose my tuple was filled with objects of type Foo:

#include <tuple>

using namespace std;

template <typename ...> void bar(); // Definition omitted.

template <typename ... Ts>
struct Foo {
  void doit() { bar<Ts...>(); }
  int rank;
};

int main(int argc, char *argv[])
{
  auto tup = make_tuple(Foo<int,double>(),
                        Foo<bool,char,float>());
  get<0>(tup).rank = 2;
  get<1>(tup).rank = 1;
  return 0;
}

I would like to be able to traverse the list of Foo types, calling their doit methods, but in an arbitrary order defined by, say, the value of the rank member.