浅层复制与深层复制

浅层复制：利用默认复制构造函数，在析构时会出错（因为析构了两遍）

深层复制：利用成员函数

题目：
1.

T& operator[](unsigned int i) ;
T& operator[](unsigned int i)const; //为什么用 const？

DynamicArray<int> iarray(length,-1);
DynamicArray<double> darray(length,-2.1);
const DynamicArray<char> carray(length,'c');

2.重载 = 运算符
先判断是否是同一个对象；

template <typename T>
DynamicArray<T>& DynamicArray<T>::operator= (const DynamicArray<T> & anotherDA) {
	if(this == &anotherDA) {
		cout<<endl<<"operator = is called";
		return *this;
	}
	mallocSize = anotherDA.mallocSize;
	array = new T[anotherDA.mallocSize];
	for(int i = 0; i < anotherDA.mallocSize; i ++) array[i] = anotherDA.array[i];
	cout<<endl<<"operator = is called";
	return *this;
}