// Demonstrating use of functors or function objects with STL


#include <list.h>
#include <algo.h>
#include <assert.h>

void show_int (int x)
{
  cout << x << " ";
}

// a function object is a class which overloads the
// function call () operator
// Like a function, you can "call" a function object
// It can be used as a predicate, etc. in STL algorithm calls
// A function object is MORE powerful than a function
// because you can package additional data with an object

class greater_than_x
{
public:
  greater_than_x(int v) { val=v; }
  bool operator() (int a) { return a > val ? true : false ; }
private:
  int val;
};


int main()
{
  cout << "Demonstrating Function Objects with lists." << endl;

  list<int> list2;

  // populating the list using "push_back"
  list2.push_back(89);
  list2.push_back(99);
  list2.push_back(89);
  list2.push_back(69);
  list2.push_back(64);
  list2.push_back(89);
  list2.push_back(89);
  list2.push_back(49);

  cout << "LIST2 Elements: " ;
  for_each(list2.begin(), list2.end(), show_int);
  cout << endl;

  list<int>::iterator ip;

  ip = find_if(list2.begin(), list2.end(), greater_than_x(90));
  if (ip !=list2.end())
    cout << "The first number greater than 90 is: " << *ip << endl;
  else
    cout << "No number greater than 90 in list2" << endl;

  ip = find_if(list2.begin(), list2.end(), greater_than_x(100));
  if (ip !=list2.end())
    cout << "The first number greater than 100 is: " << *ip << endl;
  else
    cout << "No number greater than 100 in list2" << endl;

  cout << "Count of numbers > 40: " 
       << count_if(list2.begin(), list2.end(), greater_than_x(40)) 
	 << endl;

  cout << "Count of numbers > 80: " 
       << count_if(list2.begin(), list2.end(), greater_than_x(80)) 
	 << endl;


}