Program does not print the elements of the copied stack

[Bopaki]

The original stack (myStack) prints elements well on the screen.
The copied stack (yourStack) prints nothing on the screen>

  #include<iostream>
#include<string>
#include<stack>
#include<cstddef>
#include<cassert>

using namespace std;
typedef string ItemType;

class Stack {
public:
	// Creates an empty stack.
	Stack();

	// Makes a "deep" copy of another stack, i.e. it copies
	// all the values in the stack.
	// Note that if this copy constructor is not included
	// then C++ makes a simple default copy constructor
	// that does a "shallow" copy, i.e. the default
	// copy constructor only copies the head
	// pointer (and not the stack elements).
	Stack(const Stack& other);

	// Completely destroys a stack.
	~Stack();

	// Pre:
	// Post: returns true if this stack is empty, and
	//       false otherwise
	bool empty() const;

	// Pre:
	// Post: x is put on the top of the stack
	void push(const ItemType& x);

	// Pre: stack is not empty
	// Post: returns a copy of the item on top of the stack;
	//       does *not* remove the item from the stack
	ItemType top() const;

	// Pre: stack is not empty
	// Post: deletes the top element of the stack
	void remove_top();

	// Pre: stack is not empty
	// Post: removes the top item of the stack and returns it
	ItemType pop();

private:
	struct Node {
		ItemType val;
		Node* next;

		Node(const ItemType& vv, Node* nn) : val(vv), next(nn) { }
		Node(const ItemType& vv) : val(vv), next(0) { }
	};

	Node* head;
};
// Makes a "deep" copy of another stack.
// It's interesting to note that this is, by far, the most complicated
// function in Stack, and it's only needed to prevent Stacks from
// being copied incorrectly by the default copy constructor C++
// automatically creates.
Stack::Stack()
{
   head = NULL;
    }
Stack::Stack(const Stack& other)
 {
	if (other.empty())
    {
		head = NULL;
	} else
	 {
		Node* p = other.head;          // points to current node on other
		Node* tmp = new Node(p->val);  // make a copy of the first node
		head = tmp;
		Node* tail = tmp;              // points to last node of this list
		while (p->next != NULL)
		{
			p = p->next;
			tmp = new Node(p->val);
			tail->next = tmp;
			tail = tmp;
        }
	}
 }
bool Stack::empty() const
{
    return (head == NULL);
}
//void push(const ItemType& x)
//{
  // ItemType *newNode;
    //newNode = new ItemType;
  //  assert(newNode != NULL);
  //  newNode->val = x;
  //  newNode->next = top();
  //  top() = newNode;
//}//end push
//};
// Pre:
// Post: x is put on the top of the stack
void Stack::push(const ItemType& x)
 {
	Node* tmp = new Node(x, head);
	head = tmp;
}
// Pre: stack is not empty
// Post: returns a copy of the item on top of the stack;
//       does *not* remove the item from the stack
ItemType Stack::top() const {
	if(!empty());
	return head->val;
}

// Pre: stack is not empty
// Post: deletes the top element of the stack
void Stack::remove_top() {
	if(!empty());
Node*temp = head;
	head = head->next;
	delete temp;
}
// Completely destroys a stack.
Stack::~Stack() {
	while (!empty()) remove_top();
}
//Pre: stack is not empty
//Post: removes the top item of the stack and returns it
ItemType Stack::pop()
{
    //assert(!empty());
    ItemType result = top();
    remove_top();
    return result;
}
int main()
{
 	//cout<<"See Programming Exercise 1"<<endl;
	Stack myStack;
	//Stack yourStack;
	myStack.push("summer");
	myStack.push("automn");
	myStack.push("winter");
	myStack.push("fall");
	myStack.push("spring");

	while(!myStack.empty()) //didn't look... you should have an empty checker member somewhere
{
      cout << myStack.pop() << endl;
}
    Stack yourStack(myStack);
    while(!yourStack.empty())
    {
        cout <<yourStack.pop() << endl;
    }

	return 0;
}

Here is the output:

spring
fall
winter
automn
summer

Process returned 0 (0x0)   execution time : 0.060 s
Press any key to continue.

Help as to why yourStack does not print on the screen would be appreciated:

[lastchance]

You just copied an empty stack!

You know ... the one you emptied by pop'ping whilst printing it out!

[TheIdeasMan]

The compiler says:

In member function 'ItemType Stack::top() const':
114:14: warning: suggest braces around empty body in an 'if' statement [-Wempty-body]
In member function 'void Stack::remove_top()':
121:14: warning: suggest braces around empty body in an 'if' statement [-Wempty-body]

Always use braces, even if there is only 1 statement. Do you see what happened?

When I fix those problems, then this happens:

In member function 'void Stack::remove_top()':
122:6: warning: unused variable 'temp' [-Wunused-variable]
124:9: error: 'temp' was not declared in this scope In member function 'ItemType Stack::top() const': 116:1: warning: control reaches end of non-void function [-Wreturn-type]

This is a similar problem.



Also don't use NULL , use nullptr instead.

Oh yeah, what lastchance said *facepalm* :+D

[Bopaki]

Thank you very much again good people.
Your help is greatly valued.
I simply re-pushed all the elements from myStack and the program worked fine

Stack myStack;
	//Stack yourStack;
	myStack.push("summer");
	myStack.push("automn");
	myStack.push("winter");
	myStack.push("fall");
	myStack.push("spring");

	while(!myStack.empty()) //didn't look... you should have an empty checker member somewhere
{
      cout << myStack.pop() << endl;
}
    myStack.push("summer");
	myStack.push("automn");
	myStack.push("winter");
	myStack.push("fall");
	myStack.push("spring");

    Stack yourStack(myStack);
    cout << endl << "Now printing yourStack" << endl;
    while(!yourStack.empty())
    {
        cout << yourStack.pop() << endl;
    }

[TheIdeasMan]

I simply re-pushed all the elements from myStack and the program worked fine

But you still need to fix the things I mentioned.