#ifndef FALSE
#define FALSE 0
#endif
#ifndef NULL
#define NULL 0
#endif

template<class T>
    class Gstack {
    public:
    	virtual void push(T) = 0; 	// pure virtual function
    	virtual T pop() = 0; 		// pure virtual function
    	virtual bool isempty() = 0;	// pure virtual function
    	virtual bool isfull() = 0; 	// pure virtual function
    };

#include <assert.h>
template<class T>
    class Array_stack : public Gstack<T> {
    	int sz;
    	int top;
    	T* astack;
    public:
    	Array_stack(int Nitems = 100)
    		{ sz = Nitems; astack = new T[sz]; top = sz; }
    	~Array_stack() 
		    { delete[] astack; }
    	void push(T x) 
		    { assert( !isfull() ); astack[--top] = x; }
    	T pop() 
		    { assert( !isempty() ); return( astack[top++] ); }
    	bool isempty() 
		    { return( top == sz ); }
    	bool isfull() 
		    { return( top == 0 ); }
    };

template<class T>
    class Link_stack : public Gstack<T> {
    	struct node {
    		T data;
    		node* next;
    		node(T d, node* n) 
			    { data = d; next = n; }
    	};
    	node* top;
    public:
    	Link_stack( int Nitems = 100 ) 
		    { top = NULL; }
    	void push(T x) 
		    { top = new node(x, top); }
    	T pop() {
        	assert( !isempty() );
        	T t = top -> data;
        	node* oldtop = top;
        	top = top -> next;
        	delete oldtop;
        	return t;
    	}

    	bool isempty() 
		    { return( top == NULL ); }
    	bool isfull() 
		    { return( FALSE ); }
    };

#include <iostream.h>
//#include "Vstack.h"
// Doesn't know about Arraystack or Linkedstack
//void reverse( Gstack<int> &, int );	// a prototype

template <class T>
void reverse( Gstack<T> &s, int n )
{
        int i;

        for( i = 0; i < n; i++ ) {
                s.push((T)('a'+i));
        }
        for( i = 0; i < n; i++ ) {
                cout << s.pop() << ' ';
        }
        cout << endl;
}
//#include "Vstack.h"
//#include "Linkedstack.h"
//#include "Arraystack.h"
//extern void reverse( stack<int> &s, int n );

int main()
{
	Array_stack<int> s1(500);
	Link_stack<int> s2;	        // or s2(137); but not s2();
	Array_stack<char> s3;
	Link_stack<char> s4(50);

	reverse (s1, 20);
	reverse (s2, 20);
	reverse (s3, 20);	//problem reverse only knows about integers
	reverse (s4, 20);	//need to make reverse a member function, perhaps?
	return 0;
}
/*	
//////////////Code Warrior 12 says:////////////////
Warning : variable 'Nitems' is not used in function
TStack.cc line 90   void main()

Warning : variable 'Nitems' is not used in function
TStack.cc line 90   void main()

116 115 114 113 112 111 110 109 108 107 106 105 104 103 102 101 100 99 98 97 
116 115 114 113 112 111 110 109 108 107 106 105 104 103 102 101 100 99 98 97 
t s r q p o n m l k j i h g f e d c b a 
t s r q p o n m l k j i h g f e d c b a 
*/
/*
/////////////g++ says//////////////
TStack.cc:91: warning: return type for `main' changed to integer type
TStack.cc:36: warning: `class Array_stack<int>' has virtual functions
	but non-virtual destructor
TStack.cc:36: warning: `class Array_stack<char>' has virtual functions
	but non-virtual destructor
TStack.cc: In function `int main(...)':
TStack.cc:97: type unification failed for function template `template
	<class T> void reverse(Gstack<...> &, int)'
TStack.cc:98: type unification failed for function template `template
	<class T> void reverse(Gstack<...> &, int)'
TStack.cc:99: type unification failed for function template `template
	<class T> void reverse(Gstack<...> &, int)'
TStack.cc:100: type unification failed for function template `template
	<class T> void reverse(Gstack<...> &, int)'
TStack.cc: In method `Link_stack<int>::Link_stack(int)':
TStack.cc:49: warning: unused parameter `int Nitems'
TStack.cc: In method `Link_stack<char>::Link_stack(int)':
TStack.cc:49: warning: unused parameter `int Nitems'

*/