/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */

#include "ns3/callback.h"

#include "ns3/assert.h"

#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) {

  }

};

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

  NS_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

  NS_ASSERT (!two.IsNull ());

  // invoke MyCb::cbTwo through callback instance

  int retTwo;

  two = MakeNullCallback<int, double> ();

  // invoking a null callback is just like

  // invoking a null function pointer:

  // it will crash.

  //int retTwoNull = two (20.0);

  NS_ASSERT (two.IsNull ());

#if 0

  // The below type mismatch between CbOne() and callback two will fail to 

  // compile if enabled in this program.

  two = MakeCallback (&CbOne);

#endif

#if 0

  // This is a slightly different example, in which the code will compile

  // but because callbacks are type-safe, will cause a fatal error at runtime 

  // (the difference here is that Assign() is called instead of operator=)

  Callback<void, float> three;

  three.Assign (MakeCallback (&CbOne));

#endif

  return 0;

}