Code:
#include<iostream.h>

class Num
{

public:
	Num(int num)
	{
		_num = num;
	}

	int GetNum()
	{
		return _num;
	}

	void DoSomething()
	{
		_num += GetNum(); /*Is this more expensive or the same as _num += _num? *
						  When calling GetNum, the function does not have to prepare
						  its own local stack but has to pop the value from the stack
						  local to the class, which is the same cost as accessing the 
						  private variable _num directly. However, the caller has to 
						  record its state before the call and also its return address.
						  Thoughts please.*/
	}

private:
	int _num;

};