Thread: Help with Class and Pointer Syntax

push() usually adds an element to a stack, whereas pop() usually removes the last element added to the stack. It depends on how the stack is implemented what the return value of pop() is. In the STL stack class pop() has return type void, meaning you must call top() to get the value of the top element in the stack, then call pop() if you want to remove it.

tower.top()->Draw(m_window, x, y);
tower.pop();

might work if you are using the STL stack class. Like Zach said, if you have created your own stack class, then we will need to see how you have implemented the pop() function.

Originally Posted by swoopy

So are you saying you need to temporarily pop() each HTblock off tower, do a Draw, then push back onto the stack?

If yes, then maybe you need a second stack to store each HTblock as you pop it. Something like:

Code:

stack<HTblock> Stack;
while (!tower.empty())
{
   HTblock item = tower.pop();
   item.Draw();
   Stack.push(item);
}

This is essentailly what i have to do (sorry I wasnt clearer) however my code isnt working. This is my code:

Code:

Stack *temptower = (Stack *) new Stack;
	for (int j = 0; j < (tower->GetLength()); j++){
	temptower->Push(tower->Pop());
	}	
	HTblock *temp_block;
	for (int k = 0; k < (temptower->GetLength()); k++){
	temp_block = temptower->Pop();
	temp_block->Draw(m_window, x_base, (y_base - (k * 20)));
	tower->Push(temp_block);
	}

where tower is the stack originally with the HTblock pointers. However when i go to compile this the third last line gives me an error saying "=, cannot convert from StackItemType to HTblock", if need be i can post the stack code, thanks for the help,
Cram

okay here is my stack code, unfortunetly it uses a list class but hopefully you should be able to figure it out without seeing the list code:
Stack header:

Code:

#pragma once
#include "list.h"

typedef ListItemType StackItemType;

class Stack
{
public:
	Stack(void);
	~Stack(void);
	void Push(StackItemType item);
	StackItemType Pop(void);
	StackItemType Peek(void);
	inline bool IsEmpty() const { return m_container.IsEmpty();}
	inline bool IsFull()  const { return m_container.IsFull();}
	inline int GetLength() const { return m_container.GetLength();}
private:
	int m_top;
	List m_container;
};

Stack Source Code:

Code:

#include "StdAfx.h"
#include ".\stack.h"

Stack::Stack(void)
{
	m_top = 0;
}

Stack::~Stack(void)
{
}

void Stack::Push(StackItemType item)
{
	m_top++;
	m_container.Insert(m_top, (ListItemType) item );
}

StackItemType Stack::Pop(void)
{
	StackItemType s;
	if (IsEmpty()) return NULL;
	m_container.Retrieve(m_top, (ListItemType *) &s );
	m_container.Remove(m_top);
	m_top--;
	return s;
}

StackItemType Stack::Peek(void)
{
	StackItemType s;
	if (IsEmpty()) return NULL;
	m_container.Retrieve( m_top, (ListItemType *) &s );
	return s;
}

If you could solve my question thatd really help me out thanks

Originally Posted by quzah

If I understand correctly, you have a stack, and you want to draw the whole thing, and then have the stack the way it was before you drew it. If so, do as swoopy suggested:

Code:

Stack tempstack;
StackItem item;
while( !origionalstack.isEmpty() )
{
    item = origionalstack.pop();
    draw( item );
    tempstack.push( item );
}

while( !tempstack.isEmpty() )
{
    origionalstack.push( tempstack.pop() );
}

Quzah.

essentaially thats what ive done except with the pointer stuff its not working. This line

Code:

item = origionalstack.pop();

is not functioning. Thanks

Originally Posted by swoopy

Here's a puzzling question. How did you create tower with HTblock pointers? If tower is a stack, it would consist of StackItemType's or ListItemType's. It appears from this error:
"=, cannot convert from StackItemType to HTblock"
that HTblock is not the same as a StackItemType.

Now I suppose if they are the same size you could do a cast:
temp_block = (HTblock) temptower->Pop();
or if it's a pointer:
temp_block = (HTblock *) temptower->Pop();

yah that last line seems to work thanks