/* -*-    Mode:C++; c-basic-offset:4; tab-width:4; indent-tabs-mode:nil -*- */
#include "ns3/callback.h"
#include <cassert>
#include <iostream>

using namespace ns3;

static double 
cbOne (double a, double b)
{
    std::cout << "invoke cbOne a=" << a << ", b=" << b << std::endl;
    return a;
}

class MyCb {
public:
    int cbTwo (double a) {
        std::cout << "invoke cbTwo a=" << a << std::endl;
        return -5;
    }
};


int main (int argc, char *argv[])
{
    // return type: double
    // first arg type: double
    // second arg type: double
    Callback<double, double, double> one;
    // build callback instance which points to cbOne function
    one = makeCallback (&cbOne);
    // this is not a null callback
    assert (!one.isNull ());
    // invoke cbOne function through callback instance
    double retOne;
    retOne = one (10.0, 20.0);

    // return type: int
    // first arg type: double
    Callback<int, double> two;
    MyCb cb;
    // build callback instance which points to MyCb::cbTwo
    two = makeCallback (&MyCb::cbTwo, &cb);
    // this is not a null callback
    assert (!two.isNull ());
    // invoke MyCb::cbTwo through callback instance
    int retTwo;
    retTwo = two (10.0);    

    two = makeNullCallback<int, double> ();
    // invoking a null callback is just like
    // invoking a null function pointer:
    // it will crash.
    //int retTwoNull = two (20.0);
    assert (two.isNull ());

    return 0;
}