stack and queue commenting

[connerrichards95]

I am having difficulty in adding well explained comments to this code. does anyone have any help please or guidance?

#include <iostream>
using namespace std; 


template<typename T>
class Node
{
public:
	T value;
	Node *pNext = nullptr;
	Node *pPrevious = nullptr;
};

template <typename T>
class Stack
{
public:

	~Stack(void);
	void Push(T value);
	Node<T>* NodePop(void);
	T Pop(void);
protected:
	int count = 0;
	Node<T> *pTop = nullptr;
};

template <typename T>
Stack<T>::~Stack(void)
{
	while (pTop != nullptr) { delete NodePop(); }
}

template <typename T>

Node<T>* Stack<T>::NodePop(void)
{
	Node<T> *pTmp = pTop;
	if (pTop != nullptr) pTop = pTop->pNext;
	return pTmp;
}

template <typename T>

void Stack<T>::Push(T value)
{
	Node<T>* pTmp = new Node<T>;
	pTmp->value = value;
	pTmp->pNext = pTop;
	pTop = pTmp;

}

template <typename T>

T Stack<T>::Pop(void)
{
	Node<T> *pTmp = NodePop();
	int ret = 0;

	if (pTmp != nullptr)
	{
		ret = pTmp->value;
	}
	else
	{
		throw "Stack Empty";
	}
	delete pTmp;

	return ret;
}

template <typename T>
class Queue : protected Stack<T>
{
private:
	Node<T> *pFront;
public:
	Queue(void);
	~Queue(void);
	virtual void enqueue(T value);
	virtual Node<T>* nodeDequeue(void);
	virtual T dequeue(void);
};

template<typename T>
void Queue<T>::enqueue(T value)
{
	this->Push(value);

	if (pFront == nullptr) pFront = pTop;
	else (pTop->pNext)->pPrevious = pTop;
}
template<typename T>
Queue<T>::Queue(void)
{
	pFront = pTop = nullptr;
}

template<typename T>
Queue<T>::~Queue(void)
{
	//uses stack destructor
}
template<typename T>
Node<T>* Queue<T>::nodeDequeue(void)
{
	Node<T> *pTmp = pFront;
	if (pFront != nullptr)
	{
		pFront = pFront->pPrevious;
		if (pFront != nullptr) pFront->pNext = nullptr;
	}
	return pTmp;
}

template<typename T>
T Queue<T>::dequeue(void)
{
	Node<T> *pTmp = nodeDequeue();
	T ret = 0;

	if (pTmp != nullptr)
	{
		ret = pTmp->value;
	}
	else
	{
		throw "Queue Empty";
	}
	if (pFront == nullptr) pTop = pFront; //last node has been removed
	delete pTmp;
	return ret;
}

int main(void)
{
	Stack<int> MyStack;
	Queue<int> MyQueue;

	for (int count = 0; count < 20; count++)
	{
		MyStack.Push(count);
		MyQueue.enqueue(count);
	}
	try
	{
		cout << "Stack output:" << endl;

		while (true)
		{
			cout << MyStack.Pop() << " ";
		}

	}
	catch (...)
	{
		cout << endl;
	}

	try
	{
		cout << "Queue output:" << endl;

		while (true)
		{
			cout << MyQueue.dequeue() << " ";
		}
	}
	catch (...)
	{
		cout << endl;
	}
	return 0;
}

[gunnerfunner]

if you wrote this program yourself then ask yourself what made your write each bit of it the way you did and jot down those thoughts - this will give you the material you need to make comments out of

[TheIdeasMan]

IMO, a lot of your code doesn't really need comments. If one chooses meaningful names for variables and functions, then the code itself tells a story of what is happening - so well done there :+)

Comments can be handy to explain why something is being done; invariants; expected ranges of values; pre and post conditions.

Btw, there has never been a requirement in C++ for void as function parameter, just leave it empty.

This looks a bit sketchy - Does it work? I see it throws when the end is reached, that's not a good use for an exception.

	while (true)
		{
			cout << MyStack.Pop() << " ";
		}

I am not keen on infinite loops with no obvious exit in the code.

Ideally, one would define iterators, then use a range based for loop to do things like print all the elements.

The catch clauses are pointless at the moment, at least print what the error is.

Good Luck !!