#include <assert.h>
#include <iostream>

class Istack {
	int sz;
	int top;
	int* stack;
public:
	// member function prototypes
	void init(int );
	void push(int );
	int pop();
	bool isempty();
	bool isfull();
};
/*
class Pstack {
	class node {
	public:
		int data;
		node* next;
	};
	node* new_node(int , node* );
	node* top;
public:
	// Note that the stack is implicit
	void init(int nitems );
	void push(int x);
	int pop();
	bool isempty();
	bool isfull();
};
*/

// Array implementation of stacks. 
// Grow from high index towards 0.

void Istack :: init(int nitems = 100)
{
        sz = nitems;
        stack = new int[sz];
        top = sz;
}
void Istack :: push(int x)
{
        assert( !isfull() );
        stack[--top] = x;
}
int Istack :: pop()
{
        assert( !isempty() );
        return( stack[top++] );
}
bool Istack :: isempty()
{
        return( top == sz );
}
bool Istack :: isfull()
{
        return( top == 0 );
}


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();
}