template <class T>
class bag
{
	public:
		typedef T value_type;
		
		......
		
		void merge_sort(int p, int r);
		
		void merge(int p, int q, int r);
		
		void quick_sort(int p, int r);
		
		void partition(int p, int r, int& q);
		
		void print_bag();
		
		void print_bag(char* file_name);

   private:
		int max;		// amount of available space
		int used;			// number of elements in the list
		T* array;				// the dynamic array

		void reserve(int n, bool copy);
			// called by public functions only if n > max. expands
			// the bag capacity to n elements, copies the existing
			// elements to the new space if copy == true, and deletes
			// the old dynamic array. exits if memory allocation fails.
};