#include <assert.h>
#include <iostream.h>
/////////////////////////////mydefs1.h//////////////
class Istack {
	int sz;
	int top;
	int* stack;
public:
	// Using only default constructor
	void init(int ) ;
	
	void push(int ) ;
	
	int pop() ;
	
	bool isempty() ;
	
	bool isfull() ;
	
};

/////////////////////////stack1.cc////////////////

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

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 );
}

//////////////////////stackmain1.cc//////////

void main()
{
	Istack s1;		// default constructor?		
		s1.init(500);
	Istack s2; 		// default constructor?
		s2.init;
	Istack s3(); 	// a function which returns Istack
	Istack s6;
		s6.init(137); 
	Istack s4[5]; 	// default constructor called 5 times here
	Istack* s5;		// no space, just a pointer

	int i;

	
	for( i = 0; i < 20; i++ ) {
		s1.push(i);			// s1 is a 500 element stack
	}

	for( i = 0; i < 20; i++ ) {
		cout << s1.pop() << ' ';
	}
	cout << endl;
	
	//		Everything is OK up to here, but there are problems
	//		with both of the following, depending on system used
	
	s4[3].push(11);		// 3rd stack in the array
	cout << s4[3].pop() << ' ';
	
	s5 = new Istack;		// get stack space, which constructor?
	s5->push(12);			// pointing to a stack
	cout << s5->pop() << endl;
	delete s5;				// explicit removal
}
/*
19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 
Assertion (!isfull()) failed in "stack1.cc" on line 15
*/