Axon in C++

Axon is the core of Kamaelia - the stuff that co-ordinates everything else, ensuring messages go from outboxes to their recipients' inboxes and running the components in turn. Kamaelia is primarily written in Python but there is proof-of-concept code for C++ in the CVS.
I've been creating my own (not-so-)MiniAxon in C++, focusing on efficiency unless it would overcomplicate the API. A Kamaelia implementation in C++ must provide much that the Python developer takes for granted. For example, Duff's device serves as a potent and yet intrinsically sinful implementation of generators:

#include <iostream>

static int generatorstate = 0, x = 1;
int generator()
{
  switch (generatorstate)
  {
  case 0:
     std::cout << "Hello World\n";
     generatorstate = 1; return 1;
  case 1:
     for (;;)
     {
        std::cout << x << "\n";
        x = x + 1;
        generatorstate = 2; return 1;
  case 2:
        std::cout << x << "\n";
        x = x * x;
        generatorstate = 3; return 1;
  case 3:
        ;
     }
  }
}

int main()
{
  generator();
  std::cout << "Run 1 time\n";
  generator();
  std::cout << "Run 2 times\n";
  generator();
  generator();
  generator();
  std::cout << "Run 5 times\n";
  generator();
  generator();
  generator();
  generator();
  generator();
  std::cout << "Run 10 times\n";
}