///////////////////mydefs2a.h/////////////

class Istack {	// not array of ints but linked list of ints
	class node {
	public:
		int data;
		node* next;
	};
	node* new_node(int , node* );	// prototype only
	node* top;
public:
	// Note pop() is a prototype
	void init(int Nitems = 100) 
	    { top = NULL; }
	void push(int x) 
	    { top = new_node(x, top); }
	int pop(); // prototype function
	bool isempty() 
	    { return( top == NULL ); }
	bool isfull() 
	    { return( FALSE ); }
};

//////////////////////////stackmain2a.cc/////////
#include <assert.h>
#include <iostream.h>

// Linked list implementation of stacks.

Istack :: node* Istack :: new_node(int d, node* n)
{
	node* t = new node;
	assert( t );
	t -> data = d;
	t -> next = n;
	return( t );
}

int Istack :: pop()
{
	assert( !isempty() );
	int t = top -> data;
	node* oldtop = top;
	top = top -> next;
	delete oldtop;
	return t;
}
void 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 
*/