党员双评结论:这个程序怎么调试啊?

#include<iostream.h>
template<class Item>
class bag
{
public:
bag(int initial_capacity=30)
{
capacity=initial_capacity;
used=0;

data=new Item[capacity];
}
bag(const bag &source){data=source.data;used=source.used;capacity=source.capacity;}
~bag(){};
int erase(Item &target)
{
int i,k=0;
for(i=0;i<used;i++)
if(data[i]==target)
{
k++;
data[i]=data[used-1];
used--;
i--;
}
return k;
}
void insert(Item &entry)
{
if(used<capacity)
{data[used]=entry;used++;}
else
reserve(used+10);
}

void operator=(bag &source)
{
data=source.data;used=source.used;capacity=source.capacity;
}

void operator+=(bag &addend)
{
data[used-1]+=addend[addend.used-1];
}

void reserve(int new_capacity)
{
if(new_capacity>used)
{
i=new_capacity-capacity;
capacity=new_capacity;
data=new Item[i];
}
}

Item grab(){}
int size(){return used;}
private:
Item *data;
int used;
int capacity;
};

void main()
{
bag<int> b(10);
}