Thread: function accepting reference as parameter?

I am trying to make a very basic copy of a vector.

when i add too many elements to the vector..all the sudden randomly it starts to behave strangely...only explanation is that maybe i am not understanding how references pass (?)

Heres a part of the code pertaining to my error...
(erased nonessential methods for forum)

Code:

//myVector.h

template <class T>
class myVector
{
public:
	myVector(const int sz = 10);
	void add(const T&);
	T operator[] (int index){ return arr[index]; }
private:
	int avail;
	T *arr;
	void expand();
};

template <class T>

template <class T>
myVector<T>::myVector(const int sz = 10)
{
	avail = 0;
	arr = new T[sz];
}

template <class T>
void myVector<T>::add(const T &in)
{
        //check to see if arr array is full, if it is then call expand function.
	if( sizeof(arr) == avail)
	{	
		expand();
	}
	arr[avail] = in;
	++avail;
}

template <class T>
void myVector<T>::expand()
{
	const int sz = sizeof(arr);
	T temp[sz];
	for(int i=0;i<sz;++i)
		temp[i] = arr[i];
	arr = new T[sz*2];
	for(int i=0;i<sz*2;++i)
		arr[i]=temp[i];
}

Now here is the code I am testing with it...(there are no compile errors in this program)
and here is the output following it.

Code:

#include <iostream>
#include "myVector.h"

using namespace std;
int main()
{
	myVector<int> al(1000);
	al.add(5);al.add(5);al.add(5);al.add(5);al.add(5);al.add(5);
	al.add(5);al.add(5);al.add(5);al.add(5);al.add(5);al.add(5);

	cout << "size : " << al.size()<< endl;
	for(int i=0;i<al.size();++i){
		cout << al[i]<<endl;
	}
}

size : 12
5
5
5
5
5
5
5
5
5
5
1444607057
5

It added a random LARGE number to the 11th slot there..(every time)

If i add one more addition to myVector..the program crashes on runtime...

what is the problem?

thank you

wow now the program works perfectly

Code:

template <class T>
void myVector<T>::expand()
{
    sizeArr = avail*2;

	T *temp = new T[avail*2];

	for(int i=0;i<avail;++i)
		temp[i] = arr[i];

	delete [] arr;
	arr = temp;
}

why do I have to delete arr beforehand? , shouldn't the array just point elsewhere now?

thanks again