stack list ADT

readme.md

老師在 CEIBA 給的 Stack list ADT (stack.cpp) 實作，我只在最後面多加了幾行

// 只多加下面幾行 
try{
   aStack.pop();
}
catch (StackException e){
      cout << e.what(); 
} 

Output

=> 1
=> 2
=> 3
=> empty pop

stack.cpp

#include <iostream>
#include <stdexcept>
#include <string>

using namespace std;
const int MAX_STACK = 50;
typedef int StackItemType;

class StackException: public exception
{
private:
	string msg;
public:
    StackException(const string & message =""):msg(message) {}
    ~StackException() throw(){};
    const char* what() const throw() { return msg.c_str(); }
};

class Stack
{
public:
	Stack();
	~Stack();
	Stack(const Stack&);
    bool isEmpty();
    void push(const StackItemType& ) throw (StackException);
    void pop() throw(StackException);
    StackItemType getTop() throw(StackException);
private:
	struct StackNode
	{
		StackItemType item;
		StackNode *next;
	};
	StackNode *topPtr;
};


// default constructor.
Stack::Stack() : topPtr(NULL) {}

// destructor
Stack::~Stack()
{
   while(!isEmpty())
	pop();
}

// copy constructor.
Stack::Stack(const Stack& aStack)
{
   if(aStack.topPtr == NULL)
      	topPtr = NULL;
   else
   {	// copy first node
	topPtr = new StackNode;
	topPtr->item = aStack.topPtr->item;
	// copy rest of list
	StackNode *newPtr = topPtr;
	for(StackNode *origPtr = aStack.topPtr->next;
		origPtr != NULL;
		origPtr = origPtr->next)
    {
		newPtr->next = new StackNode;
		newPtr = newPtr->next;
		newPtr->item = origPtr->item;
	} // end for
	newPtr->next = NULL;
   } // end if
} // end copy constructor
bool Stack::isEmpty(){
    return topPtr==NULL;
}

void Stack::push(const StackItemType& newItem) throw (StackException)
{  try {
     StackNode *newPtr = new StackNode;
     newPtr->item = newItem;
     newPtr->next = topPtr;
     topPtr = newPtr;
   } catch (bad_alloc e) { throw StackException("push failed"); }
}

void Stack::pop() throw(StackException)
{
   if(isEmpty())
	throw StackException("empty pop");
   else
   {
	StackNode *temp = topPtr;
	topPtr = topPtr->next;
	temp->next = NULL;
	delete temp;
   } 
}

StackItemType Stack::getTop() throw(StackException)
{
   if(isEmpty())
	throw StackException("empty stack");
   else
   {
	return topPtr->item;
   } 
}

int main()
{
   StackItemType anItem;   // typedef int StackItemType;
   Stack aStack;
   aStack.push(1);
   aStack.push(2);
   aStack.push(3);
   cout<<aStack.getTop()<<endl;
   aStack.pop();
   cout<<aStack.getTop()<<endl;
   aStack.pop();
   cout<<aStack.getTop()<<endl;
   aStack.pop();
   // 只多加下面幾行 
   try{
      aStack.pop();
   }
   catch (StackException e){
         cout << e.what(); 
   } 

   system("pause"); 
}