Simple Function Pointers example

This example shows how function pointers work. There is also an example of how priority queues work.

//Program tested on Microsoft Visual Studio 2008 - Zahid Ghadialy
//This program intents to show the use of function pointers
//This program also uses priority queues
#include<iostream>
#include<queue>

using namespace std;

typedef int (*fpRegCb)(int* i_p, int index);

int funcA(int *val, int index)
{
  cout<<"Func A: index = "<<index<<"   val = "<<*val<<endl;
  return (*val + 10);
}

int funcB(int *val, int index)
{
  cout<<"Func B: index = "<<index<<"   val = "<<*val<<endl;
  return (*val + 15);
}

class someSimpleListType
{
private:
  someSimpleListType(); //This cant be used
public:
  int index;
  int *value;
  fpRegCb callback;
  someSimpleListType(fpRegCb cb, int *val, int idx):value(val),index(idx)
  {
    callback = cb;
  };
  //< operator is overloaded for use with priority queues. This will
  //decide the priority of the new element, where it should be placed
  const bool operator <(const someSimpleListType& sLT) const
  {
    return (index < sLT.index);
  }
};

priority_queue <someSimpleListType> someSimpleList;

int main()
{
  int index=0;
  int *a=new int(22);
  int *b=new int(37);
  int *c=new int(62);

  //The higher the priority, higher it is in the queue
  someSimpleList.push(someSimpleListType(funcA, a, index++));
  someSimpleList.push(someSimpleListType(funcB, b, index++));
  someSimpleList.push(someSimpleListType(funcB, c, index++));
  //The last push will end up top of queue as index(priority) is greatest

  //Lets get all the elements from the list and process them
  cout<<"Test 1"<<endl;
  while(!someSimpleList.empty())
  {
    someSimpleListType &sLT = someSimpleList.top();
    cout<<"Callback["<<sLT.index<<"] = "<<sLT.callback(sLT.value,sLT.index)<<endl;
    someSimpleList.pop();
  }

  //Since the priority queue is now empty, push some more elements
  someSimpleList.push(someSimpleListType(funcA, a, index++));
  someSimpleList.push(someSimpleListType(funcB, b, index++));
  someSimpleList.push(someSimpleListType(funcB, c, index++));

  //This time we will only process funcB and ignore funcA
  cout<<endl<<"Test 2"<<endl;
  while(!someSimpleList.empty())
  {
    someSimpleListType &sLT = someSimpleList.top();
    if(sLT.callback == funcB)
    {
      cout<<"Callback["<<sLT.index<<"] = "<<sLT.callback(sLT.value,sLT.index)<<endl;
    }
    someSimpleList.pop();
  }

  return 0;
}