Multiple slots of different signatures

It is simple to have an object provide multiple signal consumer ports through operator() functions of different signatures. Here is an example:

class SignalIntFloatCollector : public signals::consumer<SignalIntFloatCollector>
{
public:    
    void operator()(int x)
    {
        last_int = x;
    }
    void operator()(float x)
    {
        last_float = x;
    }

    optional<int> last_int;
    optional<float> last_float;
}; // end class SignalIntFloatCollector

In such cases, where the operator() functions differ in their signature, standard connection operators will work out the correct connection:

signals::storage<void ()> banger;
signals::storage<void (int)> int_storage(2);
signals::storage<void (float)> float_storage(3.3f);
SignalIntFloatCollector collector;

// ---Connect the dataflow network -----------------------------
//
//
//            ,---------------.  void(float)   
//            |  int_storage  | -------------+ 
//            `--(send_slot)--'              |  
//                    ^                      |
// ,--------.  void() |                      +>,-----------.
// | banger | --------+                        | collector |
// `--------'         |                      +>`-----------'
//                    V                      |
//            ,--(send_slot)--.  void(float) | 
//            | float_storage | -------------+ 
//            `---------------'                
//
// -------------------------------------------------------------

banger
    | int_storage.send_slot()
    | float_storage.send_slot();
int_storage >>= collector;
float_storage >>= collector;

banger(); // this causes int_storage to output 2, and float_storage 3.3
BOOST_CHECK_EQUAL(collector.last_int, optional<int>(2));
BOOST_CHECK_EQUAL(collector.last_float, optional<float>(3.3f));