// Demonstrating remove and remove_if algorithm 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 remove and remove_if 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 (before removals)   : " ;
  for_each(list2.begin(), list2.end(), show_int);
  cout << endl;
  cout << "LIST2 size (before removals) : " << list2.size() << endl;

  // NOTE THAT REMOVE DOES NOT REALLY CHANGE SIZE
  // It essentially removes all occurences of an element
  // but, it leaves undefined slots at the end!!
  // remove algorithm returns the iterator position
  // at the first element after the retained elements...

  remove(list2.begin(), list2.end(), 99);
  cout << "LIST2 Elements after first removal : " ;
  for_each(list2.begin(), list2.end(), show_int);
  cout << endl;
  cout << "LIST2 size after first removal: " << list2.size() << endl;

  remove_if(list2.begin(), list2.end(), greater_than_x(60));
  cout << "LIST2 Elements after second removal: " ;
  for_each(list2.begin(), list2.end(), show_int);
  cout << endl;
  cout << "LIST2 size after second removal: " << list2.size() << endl;

}