#include <assert.h>
#include <iostream.h>
////////////////////////mydefs2.h/////////////////
class node {

	friend class Istack;
	
	int data;
	node* next;
	node(int d, node* n)
	{
		data = d;
		next = n;
	} 	// builder and initializer of node
};

class Istack {		// linked list implementation
	node* top;
public:
	void init(int Nitems = 100) 
	    { top = NULL; }
	void push(int x) 
	    { top = new node(x, top); }
	int  pop()
	{
		assert( !isempty() );
		int temp = top -> data;		// get data
		node* oldtop = top;		 	// point to old
		top = top -> next;			// unlink old
		delete oldtop;				// discard
		return temp;
	}			
	bool isempty() 
	    { return( top == NULL ); }
	bool isfull() 
	    { return( FALSE ); }	// Never Full
};

////////////////////////stackmain2.cc/////////

main()
{
	Istack s1, s2;
	int i;

	s1.init(500);
	s2.init();
	
	for( i = 0; i < 20; i++ ) {
		s1.push(i);
	}

	for( i = 0; i < 20; i++ ) {
		cout << s1.pop() << ' ';
	}
	cout << endl;
	
	s2.push(10);
	i = s2.pop();
}
/*
19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
*/