#include <assert.h>
////////////////////////mydefs1b.cc////////////
class Istack {
	int sz;
	int top;
	int* stack;
public:
	void init(int Nitems = 100) 
	    { sz = Nitems; stack = new int[sz]; top = sz; }
	void push(int x) 
	    { assert( !isfull() ); stack[--top] = x; }
	int pop()
	    { assert( !isempty() ); return( stack[top++] ); }
	bool isempty() 
	    { return(( top == sz )); }
	bool isfull() 
	    { return(( top == 0)); }
};
class Cstack { 	// Changed
	int sz;
	int top;
	char* stack; 		// Changed
public:
	// init, push, and pop are changed
	void init(int Nitems = 100) 
	    { sz = Nitems; stack = new char[sz]; top = sz; }
	void push(char x) 
	    { assert( !isfull() ); stack[--top] = x; }
	char pop() 
	    { assert( !isempty() ); return( stack[top++] ); }
	bool isempty() 
	    { return(( top == sz )); }
	bool isfull() 
	    { return(( top == 0)); }
};


////////////////////////stackmain1b.cc//////////////
#include <iostream.h>

void main()
{
	Istack s1;		// a stack of integers
	Cstack s3;		// a stack of chars
	int i;

	s1.init(500);
	s3.init();			// default size of 100
	
	for( i = 0; i < 20; i++ ) {
		s1.push(i);		// also push(s1, i);
	}
	for( i = 0; i < 20; i++ ) {
		cout << s1.pop() << ' ';
	}
	cout << endl;
	
	for( i = 0; i < 20; i++ ) {
		s3.push('a' + i);		// overloading push
	}
	for( i = 0; i < 20; i++ ) {
		cout << s3.pop() << ' ';
	}
	cout << endl;
}
/*
19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 
t s r q p o n m l k j i h g f e d c b a 
*/